Vitamin C Elimination

Vitamin C Elimination

This is a fact sheet intended for health professionals. For a reader-friendly overview of Vitamin C, see our consumer fact sheet on Vitamin C.

For information on vitamin C and COVID-19, see Dietary Supplements in the Time of COVID-19.

Introduction

Vitamin C, also known as L-ascorbic acid, is a water-soluble vitamin that is naturally present in some foods, added to others, and available as a dietary supplement. Humans, unlike most animals, are unable to synthesize vitamin C endogenously, so it is an essential dietary component [1].

Vitamin C is required for the biosynthesis of collagen, L-carnitine, and certain neurotransmitters; vitamin C is also involved in protein metabolism [1,2]. Collagen is an essential component of connective tissue, which plays a vital role in wound healing. Vitamin C is also an important physiological antioxidant [3] and has been shown to regenerate other antioxidants within the body, including alpha-tocopherol (vitamin E) [4]. Ongoing research is examining whether vitamin C, by limiting the damaging effects of free radicals through its antioxidant activity, might help prevent or delay the development of certain cancers, cardiovascular disease, and other diseases in which oxidative stress plays a causal role. In addition to its biosynthetic and antioxidant functions, vitamin C plays an important role in immune function [4] and improves the absorption of nonheme iron [5], the form of iron present in plant-based foods. Insufficient vitamin C intake causes scurvy, which is characterized by fatigue or lassitude, widespread connective tissue weakness, and capillary fragility [1,2,4,6-9].

The intestinal absorption of vitamin C is regulated by at least one specific dose-dependent, active transporter [4]. Cells accumulate vitamin C via a second specific transport protein. In vitro studies have found that oxidized vitamin C, or dehydroascorbic acid, enters cells via some facilitated glucose transporters and is then reduced internally to ascorbic acid. The physiologic importance of dehydroascorbic acid uptake and its contribution to overall vitamin C economy is unknown.

Oral vitamin C produces tissue and plasma concentrations that the body tightly controls. Approximately 70%–90% of vitamin C is absorbed at moderate intakes of 30–180 mg/day. However, at doses above 1 g/day, absorption falls to less than 50% and absorbed, unmetabolized ascorbic acid is excreted in the urine [4]. Results from pharmacokinetic studies indicate that oral doses of 1.25 g/day ascorbic acid produce mean peak plasma vitamin C concentrations of 135 micromol/L, which are about two times higher than those produced by consuming 200–300 mg/day ascorbic acid from vitamin C-rich foods [10]. Pharmacokinetic modeling predicts that even doses as high as 3 g ascorbic acid taken every 4 hours would produce peak plasma concentrations of only 220 micromol/L [10].

The total body content of vitamin C ranges from 300 mg (at near scurvy) to about 2 g [4]. High levels of vitamin C (millimolar concentrations) are maintained in cells and tissues, and are highest in leukocytes (white blood cells), eyes, adrenal glands, pituitary gland, and brain. Relatively low levels of vitamin C (micromolar concentrations) are found in extracellular fluids, such as plasma, red blood cells, and saliva [4].

Recommended Intakes

Intake recommendations for vitamin C and other nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) at the Institute of Medicine (IOM) of the National Academies (formerly National Academy of Sciences) [8]. DRI is the general term for a set of reference values used for planning and assessing nutrient intakes of healthy people. These values, which vary by age and gender [8], include:

• Recommended Dietary Allowance (RDA): Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals.
• Adequate Intake (AI): Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA.
• Estimated Average Requirement (EAR): Average daily level of intake estimated to meet the requirements of 50% of healthy individuals; usually used to assess the nutrient intakes of groups of people and to plan nutritionally adequate diets for them; can also be used to assess the nutrient intakes of individuals.
• Tolerable Upper Intake Level (UL): Maximum daily intake unlikely to cause adverse health effects.

Table 1 lists the current RDAs for vitamin C [8]. The RDAs for vitamin C are based on its known physiological and antioxidant functions in white blood cells and are much higher than the amount required for protection from deficiency [4,8,11]. For infants from birth to 12 months, the FNB established an AI for vitamin C that is equivalent to the mean intake of vitamin C in healthy, breastfed infants.

Table 1: Recommended Dietary Allowances (RDAs) for Vitamin C [8]

Age	Male	Female	Pregnancy	Lactation
0–6 months	40 mg*	40 mg*
7–12 months	50 mg*	50 mg*
1–3 years	15 mg	15 mg
4–8 years	25 mg	25 mg
9–13 years	45 mg	45 mg
14–18 years	75 mg	65 mg	80 mg	115 mg
19+ years	90 mg	75 mg	85 mg	120 mg
Smokers	Individuals who smoke require 35 mg/day more vitamin C than nonsmokers.

* Adequate Intake (AI)

Sources of Vitamin C

Food

Fruits and vegetables are the best sources of vitamin C (see Table 2) [12]. Citrus fruits, tomatoes and tomato juice, and potatoes are major contributors of vitamin C to the American diet [8]. Other good food sources include red and green peppers, kiwifruit, broccoli, strawberries, Brussels sprouts, and cantaloupe (see Table 2) [8,12]. Although vitamin C is not naturally present in grains, it is added to some fortified breakfast cereals. The vitamin C content of food may be reduced by prolonged storage and by cooking because ascorbic acid is water soluble and is destroyed by heat [6,8]. Steaming or microwaving may lessen cooking losses. Fortunately, many of the best food sources of vitamin C, such as fruits and vegetables, are usually consumed raw. Consuming five varied servings of fruits and vegetables a day can provide more than 200 mg of vitamin C.

Table 2: Vitamin C Content of Selected Foods [12]

Food	Milligrams (mg) per serving	Percent (%) DV*
Red pepper, sweet, raw, ½ cup	95	106
Orange juice, ¾ cup	93	103
Orange, 1 medium	70	78
Grapefruit juice, ¾ cup	70	78
Kiwifruit, 1 medium	64	71
Green pepper, sweet, raw, ½ cup	60	67
Broccoli, cooked, ½ cup	51	57
Strawberries, fresh, sliced, ½ cup	49	54
Brussels sprouts, cooked, ½ cup	48	53
Grapefruit, ½ medium	39	43
Broccoli, raw, ½ cup	39	43
Tomato juice, ¾ cup	33	37
Cantaloupe, ½ cup	29	32
Cabbage, cooked, ½ cup	28	31
Cauliflower, raw, ½ cup	26	29
Potato, baked, 1 medium	17	19
Tomato, raw, 1 medium	17	19
Spinach, cooked, ½ cup	9	10
Green peas, frozen, cooked, ½ cup	8	9

*DV = Daily Value. The U.S. Food and Drug Administration (FDA) developed DVs to help consumers compare the nutrient contents of foods and dietary supplements within the context of a total diet. The DV for vitamin C is 90 mg for adults and children age 4 years and older [13]. FDA does not require food labels to list vitamin C content unless vitamin C has been added to the food. Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.

The U.S. Department of Agriculture's (USDA's) FoodData Central lists the nutrient content of many foods and provides a comprehensive list of foods containing vitamin C arranged by nutrient content and by food name.

Dietary supplements

Supplements typically contain vitamin C in the form of ascorbic acid, which has equivalent bioavailability to that of naturally occurring ascorbic acid in foods, such as orange juice and broccoli [14-16]. Other forms of vitamin C supplements include sodium ascorbate; calcium ascorbate; other mineral ascorbates; ascorbic acid with bioflavonoids; and combination products, such as Ester-C®, which contains calcium ascorbate, dehydroascorbate, calcium threonate, xylonate and lyxonate [17].

A few studies in humans have examined whether bioavailability differs among the various forms of vitamin C. In one study, Ester-C® and ascorbic acid produced the same vitamin C plasma concentrations, but Ester-C® produced significantly higher vitamin C concentrations in leukocytes 24 hours after ingestion [18]. Another study found no differences in plasma vitamin C levels or urinary excretion of vitamin C among three different vitamin C sources: ascorbic acid, Ester-C®, and ascorbic acid with bioflavonoids [17]. These findings, coupled with the relatively low cost of ascorbic acid, led the authors to conclude that simple ascorbic acid is the preferred source of supplemental vitamin C [17].

Vitamin C Intakes and Status

According to the 2001–2002 National Health and Nutrition Examination Survey (NHANES), mean intakes of vitamin C are 105.2 mg/day for adult males and 83.6 mg/day for adult females, meeting the currently established RDA for most nonsmoking adults [19]. Mean intakes for children and adolescents aged 1-18 years range from 75.6 mg/day to 100 mg/day, also meeting the RDA for these age groups [19]. Although the 2001–2002 NHANES analysis did not include data for breastfed infants and toddlers, breastmilk is considered an adequate source of vitamin C [8,14]. Use of vitamin C-containing supplements is also relatively common, adding to the total vitamin C intake from food and beverages. NHANES data from 1999–2000 indicate that approximately 35% of adults take multivitamin supplements (which typically contain vitamin C) and 12% take a separate vitamin C supplement [20]. According to 1999–2002 NHANES data, approximately 29% of children take some form of dietary supplement that contains vitamin C [21].

Vitamin C status is typically assessed by measuring plasma vitamin C levels [4,14]. Other measures, such as leukocyte vitamin C concentration, could be more accurate indicators of tissue vitamin C levels, but they are more difficult to assess and the results are not always reliable [4,9,14].

Vitamin C Deficiency

Acute vitamin C deficiency leads to scurvy [7,8,11]. The timeline for the development of scurvy varies, depending on vitamin C body stores, but signs can appear within 1 month of little or no vitamin C intake (below 10 mg/day) [6,7,22,23]. Initial symptoms can include fatigue (probably the result of impaired carnitine biosynthesis), malaise, and inflammation of the gums [4,11]. As vitamin C deficiency progresses, collagen synthesis becomes impaired and connective tissues become weakened, causing petechiae, ecchymoses, purpura, joint pain, poor wound healing, hyperkeratosis, and corkscrew hairs [1,2,4,6-8]. Additional signs of scurvy include depression as well as swollen, bleeding gums and loosening or loss of teeth due to tissue and capillary fragility [6,8,9]. Iron deficiency anemia can also occur due to increased bleeding and decreased nonheme iron absorption secondary to low vitamin C intake [6,11]. In children, bone disease can be present [6]. Left untreated, scurvy is fatal [6,9].

Until the end of the 18^th century, many sailors who ventured on long ocean voyages, with little or no vitamin C intake, contracted or died from scurvy. During the mid-1700s, Sir James Lind, a British Navy surgeon, conducted experiments and determined that eating citrus fruits or juices could cure scurvy, although scientists did not prove that ascorbic acid was the active component until 1932 [24-26].

Today, vitamin C deficiency and scurvy are rare in developed countries [8]. Overt deficiency symptoms occur only if vitamin C intake falls below approximately 10 mg/day for many weeks [5-8,22,23]. Vitamin C deficiency is uncommon in developed countries but can still occur in people with limited food variety.

Groups at Risk of Vitamin C Inadequacy

Vitamin C inadequacy can occur with intakes that fall below the RDA but are above the amount required to prevent overt deficiency (approximately 10 mg/day). The following groups are more likely than others to be at risk of obtaining insufficient amounts of vitamin C.

Smokers and passive "smokers"

Studies consistently show that smokers have lower plasma and leukocyte vitamin C levels than nonsmokers, due in part to increased oxidative stress [8]. For this reason, the IOM concluded that smokers need 35 mg more vitamin C per day than nonsmokers [8]. Exposure to secondhand smoke also decreases vitamin C levels. Although the IOM was unable to establish a specific vitamin C requirement for nonsmokers who are regularly exposed to secondhand smoke, these individuals should ensure that they meet the RDA for vitamin C [4,8].

Infants fed evaporated or boiled milk

Most infants in developed countries are fed breastmilk and/or infant formula, both of which supply adequate amounts of vitamin C [8,14]. For many reasons, feeding infants evaporated or boiled cow's milk is not recommended. This practice can cause vitamin C deficiency because cow's milk naturally has very little vitamin C and heat can destroy vitamin C [6,12].

Individuals with limited food variety

Although fruits and vegetables are the best sources of vitamin C, many other foods have small amounts of this nutrient. Thus, through a varied diet, most people should be able to meet the vitamin C RDA or at least obtain enough to prevent scurvy. People who have limited food variety—including some elderly, indigent individuals who prepare their own food; people who abuse alcohol or drugs; food faddists; people with mental illness; and, occasionally, children—might not obtain sufficient vitamin C [4,6-9,11].

People with malabsorption and certain chronic diseases

Some medical conditions can reduce the absorption of vitamin C and/or increase the amount needed by the body. People with severe intestinal malabsorption or cachexia and some cancer patients might be at increased risk of vitamin C inadequacy [27]. Low vitamin C concentrations can also occur in patients with end-stage renal disease on chronic hemodialysis [28].

Vitamin C and Health

Due to its function as an antioxidant and its role in immune function, vitamin C has been promoted as a means to help prevent and/or treat numerous health conditions. This section focuses on four diseases and disorders in which vitamin C might play a role: cancer (including prevention and treatment), cardiovascular disease, age-related macular degeneration (AMD) and cataracts, and the common cold.

Cancer prevention

Epidemiologic evidence suggests that higher consumption of fruits and vegetables is associated with lower risk of most types of cancer, perhaps, in part, due to their high vitamin C content [1,2]. Vitamin C can limit the formation of carcinogens, such as nitrosamines [2,29], in vivo; modulate immune response [2,4]; and, through its antioxidant function, possibly attenuate oxidative damage that can lead to cancer [1].

Most case-control studies have found an inverse association between dietary vitamin C intake and cancers of the lung, breast, colon or rectum, stomach, oral cavity, larynx or pharynx, and esophagus [2,4]. Plasma concentrations of vitamin C are also lower in people with cancer than controls [2].

However, evidence from prospective cohort studies is inconsistent, possibly due to varying intakes of vitamin C among studies. In a cohort of 82,234 women aged 33–60 years from the Nurses' Health Study, consumption of an average of 205 mg/day of vitamin C from food (highest quintile of intake) compared with an average of 70 mg/day (lowest quintile of intake) was associated with a 63% lower risk of breast cancer among premenopausal women with a family history of breast cancer [30]. Conversely, Kushi and colleagues did not observe a significantly lower risk of breast cancer among postmenopausal women consuming at least 198 mg/day (highest quintile of intake) of vitamin C from food compared with those consuming less than 87 mg/day (lowest quintile of intake) [31]. A review by Carr and Frei concluded that in the majority of prospective cohort studies not reporting a significantly lower cancer risk, most participants had relatively high vitamin C intakes, with intakes higher than 86 mg/day in the lowest quintiles [2]. Studies reporting significantly lower cancer risk found these associations in individuals with vitamin C intakes of at least 80–110 mg/day, a range associated with close to vitamin C tissue saturation [2,22,32].

Evidence from most randomized clinical trials suggests that vitamin C supplementation, usually in combination with other micronutrients, does not affect cancer risk. In the Supplémentation en Vitamines et Minéraux Antioxydants (SU.VI.MAX) study, a randomized, double-blind, placebo-controlled clinical trial,13,017 healthy French adults received antioxidant supplementation with 120 mg ascorbic acid, 30 mg vitamin E, 6 mg beta-carotene, 100 mcg selenium, and 20 mg zinc, or placebo [33]. After a median follow-up time of 7.5 years, antioxidant supplementation lowered total cancer incidence in men, but not in women. In addition, baseline antioxidant status was related to cancer risk in men, but not in women [34]. Supplements of 500 mg/day vitamin C plus 400 IU vitamin E every other day for a mean follow-up period of 8 years failed to reduce the risk of prostate or total cancer compared with placebo in middle-aged and older men participating in the Physicians' Health Study II [35]. Similar findings were reported in women participating in the Women's Antioxidant Cardiovascular Study [36]. Compared with placebo, supplementation with vitamin C (500 mg/day) for an average of 9.4 years had no significant effect on total cancer incidence or cancer mortality. In a large intervention trial conducted in Linxian, China, daily supplements of vitamin C (120 mg) plus molybdenum (30 mcg) for 5–6 years did not significantly affect the risk of developing esophageal or gastric cancer [37]. Moreover, during 10 years of follow-up, this supplementation regimen failed to significantly affect total morbidity or mortality from esophageal, gastric, or other cancers [38]. A 2008 review of vitamin C and other antioxidant supplements for the prevention of gastrointestinal cancers found no convincing evidence that vitamin C (or beta-carotene, vitamin A, or vitamin E) prevents gastrointestinal cancers [39]. A similar review by Coulter and colleagues found that vitamin C supplementation, in combination with vitamin E, had no significant effect on death risk due to cancer in healthy individuals [40].

At this time, the evidence is inconsistent on whether dietary vitamin C intake affects cancer risk. Results from most clinical trials suggest that modest vitamin C supplementation alone or with other nutrients offers no benefit in the prevention of cancer.

A substantial limitation in interpreting many of these studies is that investigators did not measure vitamin C concentrations before or after supplementation. Plasma and tissue concentrations of vitamin C are tightly controlled in humans. At daily intakes of 100 mg or higher, cells appear to be saturated and at intakes of at least 200 mg, plasma concentrations increase only marginally [2,10,22,31,37]. If subjects' vitamin C levels were already close to saturation at study entry, supplementation would be expected to have made little or no difference on measured outcomes [22,23,41,42].

Cancer treatment

During the 1970s, studies by Cameron, Campbell, and Pauling suggested that high-dose vitamin C has beneficial effects on quality of life and survival time in patients with terminal cancer [43,44]. However, some subsequent studies—including a randomized, double-blind, placebo-controlled clinical trial by Moertel and colleagues at the Mayo Clinic [45]—did not support these findings. In the Moertel study, patients with advanced colorectal cancer who received 10 g/day vitamin C fared no better than those receiving a placebo. The authors of a 2003 review assessing the effects of vitamin C in patients with advanced cancer concluded that vitamin C confers no significant mortality benefit [40].

Emerging research suggests that the route of vitamin C administration (intravenous vs. oral) could explain the conflicting findings [1,46,47]. Most intervention trials, including the one conducted by Moertel and colleagues, used only oral administration, whereas Cameron and colleagues used a combination of oral and intravenous (IV) administration. Oral administration of vitamin C, even of very large doses, can raise plasma vitamin C concentrations to a maximum of only 220 micromol/L, whereas IV administration can produce plasma concentrations as high as 26,000 micromol/L [47,48]. Concentrations of this magnitude are selectively cytotoxic to tumor cells in vitro [1,67]. Research in mice suggests that pharmacologic doses of IV vitamin C might show promise in treating otherwise difficult-to-treat tumors [49]. A high concentration of vitamin C may act as a pro-oxidant and generate hydrogen peroxide that has selective toxicity toward cancer cells [49-51]. Based on these findings and a few case reports of patients with advanced cancers who had remarkably long survival times following administration of high-dose IV vitamin C, some researchers support reassessment of the use of high-dose IV vitamin C as a drug to treat cancer [3,47,49,52].

As discussed below, it is uncertain whether supplemental vitamin C and other antioxidants might interact with chemotherapy and/or radiation [53]. Therefore, individuals undergoing these procedures should consult with their oncologist prior to taking vitamin C or other antioxidant supplements, especially in high doses [54].

Cardiovascular disease

Evidence from many epidemiological studies suggests that high intakes of fruits and vegetables are associated with a reduced risk of cardiovascular disease [1,55,56]. This association might be partly attributable to the antioxidant content of these foods because oxidative damage, including oxidative modification of low-density lipoproteins, is a major cause of cardiovascular disease [1,4,56]. In addition to its antioxidant properties, vitamin C has been shown to reduce monocyte adherence to the endothelium, improve endothelium-dependent nitric oxide production and vasodilation, and reduce vascular smooth-muscle-cell apoptosis, which prevents plaque instability in atherosclerosis [2,57].

Results from prospective studies examining associations between vitamin C intake and cardiovascular disease risk are conflicting [56]. In the Nurses' Health Study, a 16-year prospective study involving 85,118 female nurses, total intake of vitamin C from both dietary and supplemental sources was inversely associated with coronary heart disease risk [58]. However, intake of vitamin C from diet alone showed no significant associations, suggesting that vitamin C supplement users might be at lower risk of coronary heart disease. A much smaller study indicated that postmenopausal women with diabetes who took at least 300 mg/day vitamin C supplements had increased cardiovascular disease mortality [59].

A prospective study in 20,649 British adults found that those in the top quartile of baseline plasma vitamin C concentrations had a 42% lower risk of stroke than those in the bottom quartile [60]. In male physicians participating in the Physicians' Health Study, use of vitamin C supplements for a mean of 5.5 years was not associated with a significant decrease in total cardiovascular disease mortality or coronary heart disease mortality [61]. A pooled analysis of nine prospective studies that included 293,172 subjects free of coronary heart disease at baseline found that people who took ≥700 mg/day of supplemental vitamin C had a 25% lower risk of coronary heart disease incidence than those who took no supplemental vitamin C [62]. The authors of a 2008 meta-analysis of prospective cohort studies, including 14 studies reporting on vitamin C for a median follow-up of 10 years, concluded that dietary, but not supplemental, intake of vitamin C is inversely associated with coronary heart disease risk [55].

Results from most clinical intervention trials have failed to show a beneficial effect of vitamin C supplementation on the primary or secondary prevention of cardiovascular disease. In the Women's Antioxidant Cardiovascular Study, a secondary prevention trial involving 8,171 women aged 40 years or older with a history of cardiovascular disease, supplementation with 500 mg/day vitamin C for a mean of 9.4 years showed no overall effect on cardiovascular events [63]. Similarly, vitamin C supplementation (500 mg/day) for a mean follow-up of 8 years had no effect on major cardiovascular events in male physicians enrolled in the Physicians' Health Study II [64].

Other clinical trials have generally examined the effects on cardiovascular disease of supplements combining vitamin C with other antioxidants, such as vitamin E and beta-carotene, making it more difficult to isolate the potential contribution of vitamin C. The SU.VI.MAX study examined the effects of a combination of vitamin C (120 mg/day), vitamin E (30 mg/day), beta-carotene (6 mg/day), selenium (100 mcg/day), and zinc (20 mg/day) in 13,017 French adults from the general population [33]. After a median follow-up time of 7.5 years, the combined supplements had no effect on ischemic cardiovascular disease in either men or women. In the Women's Angiographic Vitamin and Estrogen (WAVE) study, involving 423 postmenopausal women with at least one coronary stenosis of 15%–75%, supplements of 500 mg vitamin C plus 400 IU vitamin E twice per day not only provided no cardiovascular benefit, but significantly increased all-cause mortality compared with placebo [65].

The authors of a 2006 meta-analysis of randomized controlled trials concluded that antioxidant supplements (vitamins C and E and beta-carotene or selenium) do not affect the progression of atherosclerosis [66]. Similarly, a systematic review of vitamin C's effects on the prevention and treatment of cardiovascular disease found that vitamin C did not have favorable effects on cardiovascular disease prevention [67]. Since then, researchers have published follow-up data from the Linxian trial, a population nutrition intervention trial conducted in China [38]. In this trial, daily vitamin C supplements (120 mg) plus molybdenum (30 mcg) for 5–6 years significantly reduced the risk of cerebrovascular deaths by 8% during 10 years of follow-up after the end of the active intervention.

Although the Linxian trial data suggest a possible benefit, overall, the findings from most intervention trials do not provide convincing evidence that vitamin C supplements provide protection against cardiovascular disease or reduce its morbidity or mortality. However, as discussed in the cancer prevention section, clinical trial data for vitamin C are limited by the fact that plasma and tissue concentrations of vitamin C are tightly controlled in humans. If subjects' vitamin C levels were already close to saturation at study entry, supplementation would be expected to have made little or no difference on measured outcomes [22,23,41,42].

Age-related macular degeneration (AMD) and cataracts

AMD and cataracts are two of the leading causes of vision loss in older individuals. Oxidative stress might contribute to the etiology of both conditions. Thus, researchers have hypothesized that vitamin C and other antioxidants play a role in the development and/or treatment of these diseases.

A population-based cohort study in the Netherlands found that adults aged 55 years or older who had high dietary intakes of vitamin C as well as beta-carotene, zinc, and vitamin E had a reduced risk of AMD [68]. However, most prospective studies do not support these findings [69]. The authors of a 2007 systematic review and meta-analysis of prospective cohort studies and randomized clinical trials concluded that the current evidence does not support a role for vitamin C and other antioxidants, including antioxidant supplements, in the primary prevention of early AMD [70].

Although research has not shown that antioxidants play a role in AMD development, some evidence suggests that they might help slow AMD progression [71]. The Age-Related Eye Disease Study (AREDS), a large, randomized, placebo-controlled clinical trial, evaluated the effect of high doses of selected antioxidants (500 mg vitamin C, 400 IU vitamin E, 15 mg beta-carotene, 80 mg zinc, and 2 mg copper) on the development of advanced AMD in 3,597 older individuals with varying degrees of AMD [72]. After an average follow-up period of 6.3 years, participants at high risk of developing advanced AMD (i.e., those with intermediate AMD or those with advanced AMD in one eye) who received the antioxidant supplements had a 28% lower risk of progression to advanced AMD than participants who received a placebo. A follow-up AREDS2 study confirmed the value of this and similar supplement formulations in reducing the progression of AMD over a median follow-up period of 5 years [73].

High dietary intakes of vitamin C and higher plasma ascorbate concentrations have been associated with a lower risk of cataract formation in some studies [2,4]. In a 5-year prospective cohort study conducted in Japan, higher dietary vitamin C intake was associated with a reduced risk of developing cataracts in a cohort of more than 30,000 adults aged 45–64 years [74]. Results from two case-control studies indicate that vitamin C intakes greater than 300 mg/day reduce the risk of cataract formation by 70%–75% [2,4]. Use of vitamin C supplements, on the other hand, was associated with a 25% higher risk of age-related cataract extraction among a cohort of 24,593 Swedish women aged 49–83 years [75]. These findings applied to study participants who took relatively high-dose vitamin C supplements (approximately 1,000 mg/day) and not to those who took multivitamins containing substantially less vitamin C (approximately 60 mg/day).

Data from clinical trials are limited. In one study, Chinese adults who took daily supplements of 120 mg vitamin C plus 30 mcg molybdenum for 5 years did not have a significantly lower cataract risk [76]. However, adults aged 65–74 years who received 180 mg vitamin C plus 30 mcg molybdenum combined with other nutrients in a multivitamin/mineral supplement had a 43% significantly lower risk of developing nuclear cataracts than those who received a placebo [76]. In the AREDS study, older individuals who received supplements of 500 mg vitamin C, 400 IU vitamin E, and 15 mg beta-carotene for an average of 6.3 years did not have a significantly lower risk of developing cataracts or of cataract progression than those who received a placebo [77]. The AREDS2 study, which also tested formulations containing 500 mg vitamin C, confirmed these findings [78].

Overall, the currently available evidence does not indicate that vitamin C, taken alone or with other antioxidants, affects the risk of developing AMD, although some evidence indicates that the AREDS formulations might slow AMD progression in people at high risk of developing advanced AMD.

The common cold

In the 1970s Linus Pauling suggested that vitamin C could successfully treat and/or prevent the common cold [79]. Results of subsequent controlled studies have been inconsistent, resulting in confusion and controversy, although public interest in the subject remains high [80,81].

A 2007 Cochrane review examined placebo-controlled trials involving the use of at least 200 mg/day vitamin C taken either continuously as a prophylactic treatment or after the onset of cold symptoms [81]. Prophylactic use of vitamin C did not significantly reduce the risk of developing a cold in the general population. However, in trials involving marathon runners, skiers, and soldiers exposed to extreme physical exercise and/or cold environments, prophylactic use of vitamin C in doses ranging from 250 mg/day to 1 g/day reduced cold incidence by 50%. In the general population, use of prophylactic vitamin C modestly reduced cold duration by 8% in adults and 14% in children. When taken after the onset of cold symptoms, vitamin C did not affect cold duration or symptom severity.

Overall, the evidence to date suggests that regular intakes of vitamin C at doses of at least 200 mg/day do not reduce the incidence of the common cold in the general population, but such intakes might be helpful in people exposed to extreme physical exercise or cold environments and those with marginal vitamin C status, such as the elderly and chronic smokers [81-83]. The use of vitamin C supplements might shorten the duration of the common cold and ameliorate symptom severity in the general population [80,83], possibly due to the anti-histamine effect of high-dose vitamin C [84]. However, taking vitamin C after the onset of cold symptoms does not appear to be beneficial [81].

Health Risks from Excessive Vitamin C

Vitamin C has low toxicity and is not believed to cause serious adverse effects at high intakes [8]. The most common complaints are diarrhea, nausea, abdominal cramps, and other gastrointestinal disturbances due to the osmotic effect of unabsorbed vitamin C in the gastrointestinal tract [4,8].

In postmenopausal women with diabetes who participated in the Iowa Women's Health Study, supplemental (but not dietary) vitamin C intake (at least 300 mg/day) was significantly associated with an increased risk of cardiovascular disease mortality [59]. The mechanism for this effect, if real, is not clear and this finding is from a subgroup of patients in an epidemiological study. No such association has been observed in any other epidemiological study, so the significance of this finding is uncertain. High vitamin C intakes also have the potential to increase urinary oxalate and uric acid excretion, which could contribute to the formation of kidney stones, especially in individuals with renal disorders [8]. However, studies evaluating the effects on urinary oxalate excretion of vitamin C intakes ranging from 30 mg to 10 g/day have had conflicting results, so it is not clear whether vitamin C actually plays a role in the development of kidney stones [8,85-87]. The best evidence that vitamin C contributes to kidney stone formation is in patients with pre-existing hyperoxaluria [23].

Due to the enhancement of nonheme iron absorption by vitamin C, a theoretical concern is that high vitamin C intakes might cause excess iron absorption. In healthy individuals, this does not appear to be a concern [8]. However, in individuals with hereditary hemochromatosis, chronic consumption of high doses of vitamin C could exacerbate iron overload and result in tissue damage [4,8].

Under certain conditions, vitamin C can act as a pro-oxidant, potentially contributing to oxidative damage [8]. A few studies in vitro have suggested that by acting as a pro-oxidant, supplemental oral vitamin C could cause chromosomal and/or DNA damage and possibly contribute to the development of cancer [8,88,89]. However, other studies have not shown increased oxidative damage or increased cancer risk with high intakes of vitamin C [8,90].

Other reported effects of high intakes of vitamin C include reduced vitamin B12 and copper levels, accelerated metabolism or excretion of ascorbic acid, erosion of dental enamel, and allergic responses [8]. However, at least some of these conclusions were a consequence of assay artifact, and additional studies have not confirmed these observations [8].

The FNB has established ULs for vitamin C that apply to both food and supplement intakes (Table 3) [8]. Long-term intakes of vitamin C above the UL may increase the risk of adverse health effects. The ULs do not apply to individuals receiving vitamin C for medical treatment, but such individuals should be under the care of a physician [8].

Table 3: Tolerable Upper Intake Levels (ULs) for Vitamin C [8]

Age	Male	Female	Pregnancy	Lactation
0–12 months	Not possible to establish*	Not possible to establish*
1–3 years	400 mg	400 mg
4–8 years	650 mg	650 mg
9–13 years	1,200 mg	1,200 mg
14–18 years	1,800 mg	1,800 mg	1,800 mg	1,800 mg
19+ years	2,000 mg	2,000 mg	2,000 mg	2,000 mg

*Formula and food should be the only sources of vitamin C for infants.

Interactions with Medications

Vitamin C supplements have the potential to interact with several types of medications. A few examples are provided below. Individuals taking these medications on a regular basis should discuss their vitamin C intakes with their healthcare providers.

Chemotherapy and radiation

The safety and efficacy of the use of vitamin C and other antioxidants during cancer treatment is controversial [53,91,92]. Some data indicate that antioxidants might protect tumor cells from the action of radiation therapy and chemotherapeutic agents, such as cyclophosphamide, chlorambucil, carmustine, busulfan, thiotepa, and doxorubicin [54,91,93,94]. At least some of these data have been criticized because of poor study design [52]. Other data suggest that antioxidants might protect normal tissues from chemotherapy- and radiation-induced damage [91,93] and/or enhance the effectiveness of conventional cancer treatment [95]. However, due to the physiologically tight control of vitamin C, it is unclear whether oral vitamin C supplements could alter vitamin C concentrations enough to produce the suggested effects. Individuals undergoing chemotherapy or radiation should consult with their oncologist prior to taking vitamin C or other antioxidant supplements, especially in high doses [54].

3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins)

Vitamin C, in combination with other antioxidants, may attenuate the increase in high-density lipoprotein levels resulting from combination niacin–simvastatin (Zocor®) therapy [96,97]. It is not known whether this interaction occurs with other lipid-altering regimens [54]. Healthcare providers should monitor lipid levels in individuals taking both statins and antioxidant supplements [54].

Vitamin C and Healthful Diets

The federal government's 2020-2025 Dietary Guidelines for Americans notes that "Because foods provide an array of nutrients and other components that have benefits for health, nutritional needs should be met primarily through foods. ... In some cases, fortified foods and dietary supplements are useful when it is not possible otherwise to meet needs for one or more nutrients (e.g., during specific life stages such as pregnancy)."

For more information about building a healthy dietary pattern, refer to the Dietary Guidelines for Americans and the U.S. Department of Agriculture's MyPlate.

The Dietary Guidelines for Americans describes a healthy dietary pattern as one that:

• Includes a variety of vegetables; fruits; grains (at least half whole grains); fat-free and low-fat milk, yogurt, and cheese; and oils.

  Fruits, particularly citrus fruits, fruit juices, and many vegetables are excellent sources of vitamin C. Some ready-to-eat breakfast cereals are fortified with vitamin C.

• Includes a variety of protein foods such as lean meats; poultry; eggs; seafood; beans, peas, and lentils; nuts and seeds; and soy products.
• Limits foods and beverages higher in added sugars, saturated fat, and sodium.


• Limits alcoholic beverages.


• Stays within your daily calorie needs.

References

1. Li Y, Schellhorn HE. New developments and novel therapeutic perspectives for vitamin C. J Nutr 2007;137:2171-84. [PubMed abstract]
2. Carr AC, Frei B. Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. Am J Clin Nutr 1999;69:1086-107. [PubMed abstract]
3. Frei B, England L, Ames BN. Ascorbate is an outstanding antioxidant in human blood plasma. Proc Natl Acad Sci U S A 1989;86:6377-81. [PubMed abstract]
4. Jacob RA, Sotoudeh G. Vitamin C function and status in chronic disease. Nutr Clin Care 2002;5:66-74. [PubMed abstract]
5. Gershoff SN. Vitamin C (ascorbic acid): new roles, new requirements? Nutr Rev 1993;51:313-26. [PubMed abstract]
6. Weinstein M, Babyn P, Zlotkin S. An orange a day keeps the doctor away: scurvy in the year 2000. Pediatrics 2001;108:E55. [PubMed abstract]
7. Wang AH, Still C. Old world meets modern: a case report of scurvy. Nutr Clin Pract 2007;22:445-8. [PubMed abstract]
8. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press, 2000.
9. Stephen R, Utecht T. Scurvy identified in the emergency department: a case report. J Emerg Med 2001;21:235-7. [PubMed abstract]
10. Padayatty SJ, Sun H, Wang Y, Riordan HD, Hewitt SM, Katz A, Wesley RA, Levine M. Vitamin C pharmacokinetics: implications for oral and intravenous use. Ann Intern Med 2004;140:533-7. [PubMed abstract]
11. Francescone MA, Levitt J. Scurvy masquerading as leukocytoclastic vasculitis: a case report and review of the literature. Cutis 2005;76:261-6. [PubMed abstract]
12. U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, 2019.
13. U.S. Food and Drug Administration. Food Labeling: Revision of the Nutrition and Supplement Facts Labels. 2016.
14. Bates CJ. Bioavailability of vitamin C. Eur J Clin Nutr 1997;51 (Suppl 1):S28-33. [PubMed abstract]
15. Mangels AR, Block G, Frey CM, Patterson BH, Taylor PR, Norkus EP, et al. The bioavailability to humans of ascorbic acid from oranges, orange juice and cooked broccoli is similar to that of synthetic ascorbic acid. J Nutr 1993;123:1054-61. [PubMed abstract]
16. Gregory JF 3rd. Ascorbic acid bioavailability in foods and supplements. Nutr Rev 1993;51:301-3. [PubMed abstract]
17. Johnston CS, Luo B. Comparison of the absorption and excretion of three commercially available sources of vitamin C. J Am Diet Assoc 1994;94:779-81. [PubMed abstract]
18. Moyad MA, Combs MA, Vrablic AS, Velasquez J, Turner B, Bernal S. Vitamin C metabolites, independent of smoking status, significantly enhance leukocyte, but not plasma ascorbate concentrations. Adv Ther 2008;25:995-1009. [PubMed abstract]
19. Moshfegh A, Goldman J, Cleveland L. What We Eat in America, NHANES 2001-2002: Usual Nutrient Intakes from Food Compared to Dietary Reference Intakes. Washington, DC: U.S. Department of Agriculture, Agricultural Research Service, 2005.
20. Radimer K, Bindewald B, Hughes J, Ervin B, Swanson C, Picciano MF. Dietary supplement use by US adults: data from the National Health and Nutrition Examination Survey, 1999-2000. Am J Epidemiol 2004;160:339-49. [PubMed abstract]
21. Picciano MF, Dwyer JT, Radimer KL, Wilson DH, Fisher KD, Thomas PR, et al. Dietary supplement use among infants, children, and adolescents in the United States, 1999-2002. Arch Pediatr Adolesc Med 2007;161:978-85. [PubMed abstract]
22. Levine M, Conry-Cantilena C, Wang Y, Welch RW, Washko PW, Dhariwal KR, et al. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proc Natl Acad Sci U S A 1996;93:3704-9. [PubMed abstract]
23. Levine M, Rumsey SC, Daruwala R, Park JB, Wang Y. Criteria and recommendations for vitamin C intake. JAMA 1999;281:1415-23. [PubMed abstract]
24. King, CG, Waugh, WA. The chemical nature of vitamin C. Science 1932;75:357-358.
25. Svirbely J, Szent-Györgyi A. Hexuronic acid as the antiscorbutic factor. Nature 1932;129: 576.
26. Svirbely J, Szent-Györgyi A. Hexuronic acid as the antiscorbutic factor. Nature 1932;129: 690.
27. Hoffman FA. Micronutrient requirements of cancer patients. Cancer. 1985;55 (1 Suppl):295-300. [PubMed abstract]
28. Deicher R, Hörl WH. Vitamin C in chronic kidney disease and hemodialysis patients. Kidney Blood Press Res 2003;26:100-6. [PubMed abstract]
29. Hecht SS. Approaches to cancer prevention based on an understanding of N-nitrosamine carcinogenesis. Proc Soc Exp Biol Med 1997;216:181-91. [PubMed abstract]
30. Zhang S, Hunter DJ, Forman MR, Rosner BA, Speizer FE, Colditz GA, et al. Dietary carotenoids and vitamins A, C, and E and risk of breast cancer. J Natl Cancer Inst 1999;91:547-56. [PubMed abstract]
31. Kushi LH, Fee RM, Sellers TA, Zheng W, Folsom AR. Intake of vitamins A, C, and E and postmenopausal breast cancer. The Iowa Women's Health Study. Am J Epidemiol 1996;144:165-74. [PubMed abstract]
32. Levine M, Wang Y, Padayatty SJ, Morrow J. A new recommended dietary allowance of vitamin C for healthy young women. Proc Natl Acad Sci U S A 2001;98:9842-6. [PubMed abstract]
33. Hercberg S, Galan P, Preziosi P, Bertrais S, Mennen L, Malvy D, et al. The SU.VI.MAX Study: a randomized, placebo-controlled trial of the health effects of antioxidant vitamins and minerals. Arch Intern Med 2004;164:2335-42. [PubMed abstract]
34. Galan P, Briançon S, Favier A, Bertrais S, Preziosi P, Faure H, et al. Antioxidant status and risk of cancer in the SU.VI.MAX study: is the effect of supplementation dependent on baseline levels? Br J Nutr 2005;94:125-32. [PubMed abstract]
35. Gaziano JM, Glynn RJ, Christen WG, Kurth T, Belanger C, MacFadyen J, et al. Vitamins E and C in the prevention of prostate and total cancer in men: the Physicians' Health Study II randomized controlled trial. JAMA 2009;301:52-62. [PubMed abstract]
36. Lin J, Cook NR, Albert C, Zaharris E, Gaziano JM, Van Denburgh M, et al. Vitamins C and E and beta carotene supplementation and cancer risk: a randomized controlled trial. J Natl Cancer Inst 2009;101:14-23. [PubMed abstract]
37. Taylor PR, Li B, Dawsey SM, Li JY, Yang CS, Guo W, et al. Prevention of esophageal cancer: the nutrition intervention trials in Linxian, China. Linxian Nutrition Intervention Trials Study Group. Cancer Res 1994;54(7 Suppl):2029s-31s. [PubMed abstract]
38. Qiao YL, Dawsey SM, Kamangar F, Fan JH, Abnet CC, Sun XD, et al. Total and cancer mortality after supplementation with vitamins and minerals: follow-up of the Linxian General Population Nutrition Intervention Trial. J Natl Cancer Inst 2009;101:507-18. [PubMed abstract]
39. Bjelakovic G, Nikolova D, Simonetti RG, Gluud C. Antioxidant supplements for preventing gastrointestinal cancers. Cochrane Database Syst Rev 2008;(3):CD004183. [PubMed abstract]
40. Coulter I, Hardy M, Shekelle P, Udani J, Spar M, Oda K, et al. Effect of the supplemental use of antioxidants vitamin C, vitamin E, and coenzyme Q10 for the prevention and treatment of cancer. Evidence Report/Technology Assessment Number 75. AHRQ Publication No. 04-E003. Rockville, MD: Agency for Healthcare Research and Quality, 2003. [PubMed abstract]
41. Padayatty SJ, Levine M. Vitamins C and E and the prevention of preeclampsia. N Engl J Med 2006;355:1065. [PubMed abstract]
42. Padayatty SJ, Levine M. Antioxidant supplements and cardiovascular disease in men. JAMA 2009;301:1336. [PubMed abstract]
43. Cameron E, Campbell A. The orthomolecular treatment of cancer. II. Clinical trial of high-dose ascorbic acid supplements in advanced human cancer. Chem Biol Interact 1974;9:285-315. [PubMed abstract]
44. Cameron E, Pauling L. Supplemental ascorbate in the supportive treatment of cancer: prolongation of survival times in terminal human cancer. Proc Natl Acad Sci U S A 1976;73:3685-9. [PubMed abstract]
45. Moertel CG, Fleming TR, Creagan ET, Rubin J, O'Connell MJ, Ames MM. High-dose vitamin C versus placebo in the treatment of patients with advanced cancer who have had no prior chemotherapy. A randomized double-blind comparison. N Engl J Med 1985;312:137-41. [PubMed abstract]
46. Bruno EJ Jr, Ziegenfuss TN, Landis J. Vitamin C: research update. Curr Sports Med Rep 2006;5:177-81. [PubMed abstract]
47. Padayatty SJ, Riordan HD, Hewitt SM, Katz A, Hoffer LJ, Levine M. Intravenously administered vitamin C as cancer therapy: three cases. CMAJ 2006;174:937-42. [PubMed abstract]
48. Hoffer LJ, Levine M, Assouline S, Melnychuk D, Padayatty SJ, Rosadiuk K, et al. Phase I clinical trial of i.v. ascorbic acid in advanced malignancy. Ann Oncol 2008;19:1969-74. [PubMed abstract]
49. Chen Q, Espey MG, Sun AY, Pooput C, Kirk KL, Krishna MC, et al. Pharmacologic doses of ascorbate act as a prooxidant and decrease growth of aggressive tumor xenografts in mice. Proc Natl Acad Sci U S A 2008;105:11105-9. [PubMed abstract]
50. Chen Q, Espey MG, Krishna MC, Mitchell JB, Corpe CP, Buettner GR, et al. Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues. Proc Natl Acad Sci U S A 2005;102:13604-9. [PubMed abstract]
51. Chen Q, Espey MG, Sun AY, Lee JH, Krishna MC, Shacter E, et al. Ascorbate in pharmacologic concentrations selectively generates ascorbate radical and hydrogen peroxide in extracellular fluid in vivo. Proc Natl Acad Sci U S A 2007;104:8749-54. [PubMed abstract]
52. Levine M, Espey MG, Chen Q. Losing and finding a way at C: new promise for pharmacologic ascorbate in cancer treatment. Free Radic Biol Med 2009;47:27-9. [PubMed abstract]
53. Seifried HE, Anderson DE, Sorkin BC, Costello RB. Free radicals: the pros and cons of antioxidants. Executive summary report. J Nutr 2004;134:3143S-63S. [PubMed abstract]
54. Natural Medicines Comprehensive Database. Vitamin C.
55. Ye Z, Song H. Antioxidant vitamins intake and the risk of coronary heart disease: meta-analysis of cohort studies. Eur J Cardiovasc Prev Rehabil 2008;15:26-34. [PubMed abstract]
56. Willcox BJ, Curb JD, Rodriguez BL. Antioxidants in cardiovascular health and disease: key lessons from epidemiologic studies. Am J Cardiol 2008;101:75D-86D. [PubMed abstract]
57. Honarbakhsh S, Schachter M. Vitamins and cardiovascular disease. Br J Nutr 2008:1-19. [PubMed abstract]
58. Osganian SK, Stampfer MJ, Rimm E, Spiegelman D, Hu FB, Manson JE, et al. Vitamin C and risk of coronary heart disease in women. J Am Coll Cardiol 2003;42:246-52. [PubMed abstract]
59. Lee DH, Folsom AR, Harnack L, Halliwell B, Jacobs DR Jr. Does supplemental vitamin C increase cardiovascular disease risk in women with diabetes? Am J Clin Nutr 2004;80:1194-200. [PubMed abstract]
60. Myint PK, Luben RN, Welch AA, Bingham SA, Wareham NJ, Khaw KT. Plasma vitamin C concentrations predict risk of incident stroke over 10 y in 20 649 participants of the European Prospective Investigation into Cancer Norfolk prospective population study. Am J Clin Nutr 2008;87:64-9. [PubMed abstract]
61. Muntwyler J, Hennekens CH, Manson JE, Buring JE, Gaziano JM. Vitamin supplement use in a low-risk population of US male physicians and subsequent cardiovascular mortality. Arch Intern Med 2002;162:1472-6. [PubMed abstract]
62. Knekt P, Ritz J, Pereira MA, O'Reilly EJ, Augustsson K, Fraser GE, et al. Antioxidant vitamins and coronary heart disease risk: a pooled analysis of 9 cohorts. Am J Clin Nutr 2004;80:1508-20. [PubMed abstract]
63. Cook NR, Albert CM, Gaziano JM, Zaharris E, MacFadyen J, Danielson E, et al. A randomized factorial trial of vitamins C and E and beta carotene in the secondary prevention of cardiovascular events in women: results from the Women's Antioxidant Cardiovascular Study. Arch Intern Med 2007;167:1610-8. [PubMed abstract]
64. Sesso HD, Buring JE, Christen WG, Kurth T, Belanger C, MacFadyen J, et al. Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial. JAMA 2008;300:2123-33. [PubMed abstract]
65. Waters DD, Alderman EL, Hsia J, Howard BV, Cobb FR, Rogers WJ, et al. Effects of hormone replacement therapy and antioxidant vitamin supplements on coronary atherosclerosis in postmenopausal women: a randomized controlled trial. JAMA 2002;288:2432-40. [PubMed abstract]
66. Bleys J, Miller ER 3rd, Pastor-Barriuso R, Appel LJ, Guallar E. Vitamin-mineral supplementation and the progression of atherosclerosis: a meta-analysis of randomized controlled trials. Am J Clin Nutr 2006;84:880-7. [PubMed abstract]
67. Shekelle P, Morton S, Hardy M. Effect of supplemental antioxidants vitamin C, vitamin E, and coenzyme Q10 for the prevention and treatment of cardiovascular disease. Evidence Report/Technology Assessment No. 83 AHRQ Publication No. 03-E043. Rockville, MD: Agency for Healthcare Research and Quality, 2003. [PubMed abstract]
68. van Leeuwen R, Boekhoorn S, Vingerling JR, Witteman JC, Klaver CC, Hofman A, et al. Dietary intake of antioxidants and risk of age-related macular degeneration. JAMA 2005;294:3101-7. [PubMed abstract]
69. Evans J. Primary prevention of age related macular degeneration. BMJ 2007;335:729. [PubMed abstract]
70. Chong EW, Wong TY, Kreis AJ, Simpson JA, Guymer RH. Dietary antioxidants and primary prevention of age related macular degeneration: systematic review and meta-analysis. BMJ 2007;335:755. [PubMed abstract]
71. Evans JR. Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration. Cochrane Database Syst Rev 2006;(2):CD000254. [PubMed abstract]
72. Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Arch Ophthalmol 2001;119:1417-36. [PubMed abstract]
73. The Age-Related Eye Disease Study 2 (AREDS2) Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the Age-Related Eye Disease Study 2 (AREDS2) randomized clinical trial. JAMA 2013;309:2005-15. [PubMed abstract]
74. Yoshida M, Takashima Y, Inoue M, Iwasaki M, Otani T, Sasaki S; JPHC Study Group. Prospective study showing that dietary vitamin C reduced the risk of age-related cataracts in a middle-aged Japanese population. Eur J Nutr 2007;46:118-24. [PubMed abstract]
75. Rautiainen S, Lindblad BE, Morgenstern R, Wolk A. Vitamin C supplements and the risk of age-related cataract: a population-based prospective cohort study in women. Am J Clin Nutr. 2010 Feb;91(2):487-93. [PubMed abstract]
76. Sperduto RD, Hu TS, Milton RC, Zhao JL, Everett DF, Cheng QF, et al. The Linxian cataract studies. Two nutrition intervention trials. Arch Ophthalmol 1993;111:1246-53. [PubMed abstract]
77. Age-Related Eye Disease Study Research Group. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E and beta carotene for age-related cataract and vision loss: AREDS report no. 9. Arch Ophthalmol 2001;119:1439-52. [PubMed abstract]
78. The Age-Related Eye Disease Study 2 (AREDS2) Research Group. Lutein/zeaxanthin for the treatment of age-related cataract: AREDS2 randomized trial report no. 4. JAMA Ophthalmol 2013. Online May 5. [PubMed abstract]
79. Pauling L. The significance of the evidence about ascorbic acid and the common cold. Proc Natl Acad Sci U S A 1971;68:2678-81. [PubMed abstract]
80. Douglas RM, Hemilä H. Vitamin C for preventing and treating the common cold. PLoS Med 2005;2:e168. [PubMed abstract]
81. Douglas RM, Hemilä H, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev 2007;(3):CD000980. [PubMed abstract]
82. Wintergerst ES, Maggini S, Hornig DH. Immune-enhancing role of vitamin C and zinc and effect on clinical conditions. Ann Nutr Metab 2006;50:85-94. [PubMed abstract]
83. Hemilä H. The role of vitamin C in the treatment of the common cold. Am Fam Physician 2007;76:1111, 1115. [PubMed abstract]
84. Johnston CS. The antihistamine action of ascorbic acid. Subcell Biochem 1996;25:189-213. [PubMed abstract]
85. Curhan GC, Willett WC, Rimm EB, Stampfer MJ. A prospective study of the intake of vitamins C and B6, and the risk of kidney stones in men. J Urol 1996;155:1847-51. [PubMed abstract]
86. Curhan GC, Willett WC, Speizer FE, Stampfer MJ. Intake of vitamins B6 and C and the risk of kidney stones in women. J Am Soc Nephrol 1999;10:840-5. [PubMed abstract]
87. Taylor EN, Stampfer MJ, Curhan GC. Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up. J Am Soc Nephrol 2004;15:3225-32. [PubMed abstract]
88. Lee SH, Oe T, Blair IA. Vitamin C-induced decomposition of lipid hydroperoxides to endogenous genotoxins. Science 2001;292:2083-6. [PubMed abstract]
89. Podmore ID, Griffiths HR, Herbert KE, Mistry N, Mistry P, Lunec J. Vitamin C exhibits pro-oxidant properties. Nature 1998;392:559. [PubMed abstract]
90. Carr A, Frei B. Does vitamin C act as a pro-oxidant under physiological conditions? FASEB J 1999 Jun;13:1007-24. [PubMed abstract]
91. Lawenda BD, Kelly KM, Ladas EJ, Sagar SM, Vickers A, Blumberg JB. Should supplemental antioxidant administration be avoided during chemotherapy and radiation therapy? J Natl Cancer Inst 2008;100:773-83. [PubMed abstract]
92. Ladas EJ, Jacobson JS, Kennedy DD, Teel K, Fleischauer A, Kelly KM. Antioxidants and cancer therapy: a systematic review. J Clin Oncol 2004;22:517-28. [PubMed abstract]
93. Block KI, Koch AC, Mead MN, Tothy PK, Newman RA, Gyllenhaal C. Impact of antioxidant supplementation on chemotherapeutic efficacy: a systematic review of the evidence from randomized controlled trials. Cancer Treat Rev 2007;33:407-18. [PubMed abstract]
94. Heaney ML, Gardner JR, Karasavvas N, Golde DW, Scheinberg DA, Smith EA, et al. Vitamin C antagonizes the cytotoxic effects of antineoplastic drugs. Cancer Res 2008;68:8031-8. [PubMed abstract]
95. Prasad KN. Rationale for using high-dose multiple dietary antioxidants as an adjunct to radiation therapy and chemotherapy. J Nutr 2004;134:3182S-3S. [PubMed abstract]
96. Brown BG, Zhao XQ, Chait A, Fisher LD, Cheung MC, Morse JS, et al. Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease. N Engl J Med 2001;345:1583-92. [PubMed abstract]
97. Cheung MC, Zhao XQ, Chait A, Albers JJ, Brown BG. Antioxidant supplements block the response of HDL to simvastatin-niacin therapy in patients with coronary artery disease and low HDL. Arterioscler Thromb Vasc Biol 2001;21:1320-6. [PubMed abstract]

Disclaimer

This fact sheet by the Office of Dietary Supplements (ODS) provides information that should not take the place of medical advice. We encourage you to talk to your healthcare providers (doctor, registered dietitian, pharmacist, etc.) about your interest in, questions about, or use of dietary supplements and what may be best for your overall health. Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice.

Vitamin C Elimination

Source: https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/

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Zicam Vitamin C

Zicam Vitamin C

Everything You Need to Know About Vitamin C

Medically Reviewed by Madeline Hubbard, RN, BSN.

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Whether in the form of a fizzy drink or flavored lozenges, cold and flu preventative supplements almost always highlight vitamin C as one of their key ingredients. So, what's so magical about vitamin C? Also known as ascorbic acid, vitamin C is critical to living healthily. Since the human body cannot spontaneously generate this nutrient, vitamin C must instead be absorbed from outside sources, such as vitamin supplements or foods that are naturally rich in it.

What Does Vitamin C Do?

Commonly found in cold and flu preventative supplements, vitamin C strengthens and speeds up immune system functionality. Though research does not indicate that vitamin C intake alone can prevent the onset of cold or flu, adequate daily intake may shorten the duration of an infection or lessen the severity of symptoms.

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Vitamin C is crucial for the maintenance of well being. For example, it plays a role in wound healing and helps maintain many essential body tissues. It also acts as a potent antioxidant and can repair damage from free radicals, which are linked to aging effects, and disease vulnerability. Additionally, vitamin C can also prevent anemia, since it helps the body increase absorption of dietary iron, another vital mineral that the body cannot spontaneously create.

Foods that contain high concentrations of vitamin C have been linked with a lower risk of cardiovascular disease, like heart attack and stroke. Vitamin C can also increase levels of nitric oxide, a compound that widens blood vessels and, in turn, lowers blood pressure. In addition, regular intake of vitamin C, along with other vitamins, has been linked to a decreased risk for developing age-related cataracts, a leading cause of visual impairment in the United States.

Common Sources of Vitamin C

Vitamin C can be easily obtained through the many different foods, including:

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• Citrus fruits and juices (orange, grapefruit, lemon, lime and tangerine)
• Berries
• Melons
• Mangoes
• Kiwi
• Tomato
• Broccoli
• Red peppers
• Spinach
• Squash
• Potatoes

Cooking these foods may result in the loss of some of the vitamin content, so it is ideal to ingest them raw, either whole or juiced. Nowadays, there are also numerous packaged food products, like cereals, that have been enriched and fortified with vitamin C, so that the nutrient can be easily obtained.

Vitamin C may also be labeled as "L-ascorbic acid" in supplement form, and most over-the-counter multivitamins contain the recommended daily amount of the vitamin. While it is a good source when an individual is in need of a vitamin C boost, supplements are not meant to replace a diet rich in naturally derived vitamin C.

What Happens When You Have Too Much — or Too Little — Vitamin C?

Vitamin C is a water-soluble vitamin that can be easily flushed out of the body via urination when it is not needed. Therefore, if the main source of vitamin C is from naturally occurring foods, it is near-impossible for excess vitamin C to produce side effects. However, taking excessive concentrated vitamin C supplements may lead to diarrhea or stomach upset.

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Since vitamin C-rich foods are so readily available nowadays, symptoms of inadequate vitamin C intake are also rare in the United States. However, malnourished individuals can experience symptoms of vitamin C deficiency over time, including:

• Weakness
• Fatigue
• Anemia
• Easy bruising
• Joint pain
• Skin breakdown
• Weakened tooth enamel
• Gum inflammation

Severe vitamin C deficiency is referred to as scurvy. Scurvy can be easily treated with increased dietary or supplemental vitamin C. Since vitamin C is crucial in the detoxification of the body, a lack of vitamin C can compromise the immune system and make an individual more susceptible to diseases and infections. Individuals with insufficient vitamin C may find that it takes longer than usual to recover from a cold or a physical wound.

Daily Dosage Recommendations:

The daily dosage recommendation for vitamin C is different for everyone, depending on factors such as gender, age, lifestyle and current health condition. The recommended daily dosage for vitamin C is at least 75 mg daily for women and 90 mg for men. Since people who are pregnant, breast feeding, smoking or using oral contraceptives have a lower blood level of vitamin C than others, larger doses of vitamin C may be needed to achieve optimal results in these individuals. Those who have prior or current medical conditions may also require bigger or smaller dosage levels, as recommended by their healthcare providers.

Resource Links:

• "Vitamin C" via MedlinePlus
• "Vitamin C and Infections" via MDPI
• "Extra Dose of Vitamin C Based on a Daily Supplementation Shortens the Common Cold: A Meta-Analysis of 9 Randomized Controlled Trials" via Hindawi, BioMed Research International
• "Vitamin C" via National Institutes of Health
• "Scurvy" via U.S. Department of Health & Human Services, National Institutes of Health
• "Dietary intake and blood concentrations of antioxidants and the risk of cardiovascular disease, total cancer, and all-cause mortality: a systematic review and dose-response meta-analysis of prospective studies" via The American Journal of Clinical Nutrition
• "Dietary vitamin and carotenoid intake and risk of age-related cataract" via The American Journal of Clinical Nutrition
• "Cardiovascular System" via Department of Anatomy, Seoul National University College of Medicine (via Springer)

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Is Vitamin C Good For Rosacea

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Vitamin A Facts: Everything You Need to Know

Medically Reviewed by Dr Samantha Miller, MBChB

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Vitamin A should be an integral part of every person's diet. It plays vital roles in your body by helping to maintain your vision, skin health and even your immune system's ability to work properly. But it's important to consume the right amount; vitamin A can be harmful when your body gets too much of it. Learn more about vitamin A, including what it does, where to find it and what happens when you get too much of it.

What Does Vitamin A Do?

Vitamin A is actually a group of fat-soluble vitamins like retinol, retinal and retinyl esters, all of which have various health benefits. Vitamin A is particularly important in the maintenance of vision — especially your ability to see in low light. Your body converts this vitamin to retinal, which combines with other molecules to form rhodopsin. This is the protein principally responsible for your eyes' absorption of light. If you're worried about your vision getting worse over time, make sure you get enough vitamin A. It's a good way to strengthen your sight naturally.

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Consuming sufficient amounts of vitamin A can also work wonders for your immune system. Vitamin A promotes the production of white blood cells, particularly T cells, which eliminate viruses and bacteria from your body. Vitamin A also stimulates the production of special T cells called regulatory T cells. These help to reduce the risk of your body attacking its own healthy cells, which is what happens with some autoimmune diseases. Furthermore, vitamin A fortifies the linings of your respiratory, intestinal and urinary tracts, along with your skin and mucous membranes. It also sends additional immune cells there to prevent bacteria from entering your body and causing an infection.

Vitamin A is also involved in the maintenance of healthy skin by helping immature skin cells age properly into mature skin cells. It reduces sebum production, which can be problematic in oily skin. In fact, Isotretinoin is a common prescription-only vitamin A derivative used as a treatment for acne.

Vitamin A can also contribute to improved bone growth, cell division and cell differentiation. It even promotes reproduction and is a healthy supplement for people who are breastfeeding.

Food Sources of Vitamin A

Vitamin A is quite easy to come by naturally. Many of the most basic staples in our diets — meat, eggs, milk and cheese, for example — are excellent sources of vitamin A. Other specific animal sources have high vitamin A levels as well, such as kidney and liver. However, it's important to note that some of these foods have high cholesterol and saturated fat levels, so be sure to keep a healthy balance of these in your diet if you choose to eat them.

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Vitamin A exists as either preformed vitamin A or as provitamin A carotenoids. Preformed vitamin A is found in animal and dairy sources. Provitamin A carotenoids include beta-carotene and alpha-carotene, which your body converts into vitamin A and other derivatives. Beta-carotene is found in foods like carrots, pumpkins, sweet potatoes, cantaloupes, grapefruits, spinach, broccoli and apricots. As a general rule, the more vibrant the color of a fruit or vegetable is, the more beta-carotene it contains. As a bonus, you won't have to worry about the fat or cholesterol content in these foods.

Side Effects of Too Much Vitamin A

Getting the right amount of vitamin A in your diet shouldn't have any negative side effects. However, a vitamin A deficiency can lead to health issues over time. If you don't get enough vitamin A, you could develop vision problems. Plus, your immune system could weaken, leaving you susceptible to infectious diseases.

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Perhaps even more serious are the side effects of consuming too much vitamin A, also known as hypervitaminosis A. Initially, too much vitamin A can cause headaches, dizziness, nausea and even vomiting. Because vitamin A is fat-soluble, it tends to get stored in your liver if you consume too much of it, which can lead to liver problems and even liver failure. There's also evidence that getting excess vitamin A can cause osteoporosis and bone fractures.

In particular, pregnant people must be careful about their intake of vitamin A, as getting too much vitamin A can cause birth defects. Pregnant people shouldn't eat foods that are high in vitamin A, such as pate and fish liver oil. In general, babies and small children are more sensitive to vitamin A overdoses and deficiencies, so it's important to closely monitor their daily vitamin A consumption, too.

Taking Vitamin A: Daily Dosage Recommendations

According to the Institute of Medicine Food and Nutrition Board, most adult men should consume around 900 micrograms (mcg) of vitamin A per day, and women should have around 700mcg per day. The recommended daily intake is lower (750–770mcg per day) in pregnant people and higher (1200–1300mcg per day) for people who are breastfeeding.

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The daily dosage for children varies with age. From 0 to 6 months, infants should have 400mcg per day, after which they should consume 500mcg per day until they reach the age of 1. Children 1 to 3 years of age should get 300mcg per day, while those from 4 to 8 years of age need 400mcg per day. Those from 9 to 13 years old need 600mcg each day. Daily recommendations for children don't change based on gender.

These dosage requirements are general guidelines. Individuals may have differing daily recommendations for vitamin A, depending on their health status and lifestyle. Most people can get a sufficient amount of vitamin A simply by eating a balanced diet. Consult a doctor before taking any vitamin A supplements or changing from the recommended dosage for your age and sex.

In summary, it's important to be aware of the foods that'll give you an adequate supply of vitamin A. Provided you have a balanced diet, you might not need to take vitamin A supplements. Be aware of foods containing high levels of vitamin A, and avoid eating too much of these, particularly during pregnancy.

Resource Links:

https://medlineplus.gov/vitamina.html

https://bnf.nice.org.uk/treatment-summary/vitamins.html

https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-a/

https://ods.od.nih.gov/factsheets/VitaminA-Consumer/

https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6470929/pdf/nutrients-11-00681.pdf

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Is Vitamin C Good For Rosacea

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Bliss Vitamin C Moisturizer

Bliss Vitamin C Moisturizer

A Guide to Vitamin C Serums

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For 70 years Vitamin C has been one of the biggest weapons in the skin care industry. It's used to make cleansers, moisturizers, lotions, masks, and serums. So what is this powerful vitamin? How can it benefit you? Why should you use serums that contain Vitamin C? We're here to answer all of those burning questions in this complete guide and reveal the many benefits Vitamin C serums offer for your skin.

What Are Vitamin C Serums?

There are many variations of Vitamin C, but the most popular is ascorbic acid, a common ingredient in skincare products. However, all the variations of Vitamin C have anti-inflammatory benefits.

Vitamin C Serums are products that contain a high level of Vitamin C. They're used to treat wrinkles, sagging skin, lighten dark or red spots, prevent breakouts and even your skin tone. Basically, they battle all of those annoying skin issues. There are loads of products out there that claim they'll save your skin, but some can cause damage. Vitamin C is one of the most revered ingredients and conclusive research has shown how effective it can be.

How Are Vitamin C Serums Made?

Well so far we've talked about how incredible Vitamin C is and it sounds like a dream come true doesn't it? It's not all good. In fact, the mighty vitamin is unstable when it's exposed to air and light. Other ingredients need to be used to stabilize it and allow it to deliver amazing results. The serums are combined with ferulic acid and Vitamin E. According to researchers the perfect mixture is 15% Vitamin C with 1% Vitamin E and 0.5% ferulic acid. This makes Vitamin C perform to the best of its abilities, without damaging your skin.

What Does Vitamin C Serum Do for Your Face?

Boosts Collagen Production: Collagen keeps your skin firm and prevents sagging. Environmental factors such as lifestyle choices and pollution can increase the elasticity of your skin, so it's important you try to increase your collagen production.

Hydrates Your Skin: Dry skin is a common issue, but Vitamin C can help to give your skin that much-needed moisture boost. Remember, it doesn't work immediately so you need to keep applying the serum to see results.

Brightens Your Complexion: Dark spots on your skin are caused by the overproduction of melanin. Vitamin C decreases the production and lightens the dark spots to even out your complexion.

Reduces Redness and Inflammation: Conditions such as Rosacea leave many people searching for a magic cure. Vitamin C helps facial redness and inflammation by reducing the appearance of broken capillaries.

Why Should You Be Using Vitamin C Serum?

Don't think Vitamin C serums are just beneficial for your face. They can also shield you from sun damage and reduce stretch marks.

Saves You From The Sun: Prolonged exposure to UV rays can cause long-term damage to your skin. Luckily, Vitamin C is a powerful antioxidant that reduces red sports and prevents sunburn from spreading.

Fades Acne Scars: Acne plagues most of us at some point and we look forward to being free. Most of us get stuck with some scars but Vitamin C helps to fade scars and even out any discoloration.

Reduces Stretch Marks: Yes, Vitamin C serum can even help prevent those unsightly stretch marks by tightening your skin.

Are you ready to change your skin? Add a Vitamin C serum to your beauty regimen and enjoy a glowing complexion.

Bliss Vitamin C Moisturizer

Source: https://www.bloglines.com/article/a-guide-to-vitamin-c-serums?utm_content=params%3Ao%3D740010%26ad%3DdirN%26qo%3DserpIndex

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Vitamin C Weight Loss

Vitamin C Weight Loss

Researchers in the United Kingdom say a study on eyesight shows diet and environmental factors are more important than genetics in lowering risk of cataracts.

Eating an apple a day may keep the doctor away, but eating oranges might do the same for cataracts.

In a study published today in the journal Ophthalmology, researchers in the United Kingdom said a higher dietary intake of vitamin C might significantly reduce the risk of developing cataracts.

The study, led by scientists at King's College London, is the first to conclude that dietary and environmental factors play a larger role than genetics in the development of cataracts.

"The findings of this study could have significant impact, particularly for the aging population globally by suggesting that simple dietary changes such as increased intake of fruits and vegetables as part of a healthier diet could help protect them from cataracts," Dr. Chris Hammond, professor of ophthalmology at King's College, consultant eye surgeon and lead author of the study, said in a statement.

Read More: What Is a Cataract? »

The researchers estimated genetic factors account for 35 percent of the difference in cataract progression. Environment and lifestyle account for 65 percent.

To study the impact diet has on cataracts, the researchers tracked the progression of the eye condition in 324 pairs of female twins from the United Kingdom.

The scientists examined digital images of the women's eye lenses when they were about 60 years old. They then studied the same type of images 10 years later.

They kept track of the women's intake of vitamins A, B, C, D, and E. They also tracked their intake of copper, manganese, and zinc using a food questionnaire.

The researchers said the women who ingested more vitamin C initially had a 20 percent reduced risk of developing cataracts. After 10 years, that risk had decreased by 33 percent.

The researchers noted that there was little risk reduction in the women who took vitamin supplements. Instead the preventative effects appeared to be obtained only by eating foods rich in vitamin C.

Dr. Ravi D. Goel, an ophthalmologist from New Jersey who is also a clinical instructor at Wills Eye Hospital in Pennsylvania, said the study provides helpful information for patients and doctors.

"These are novel findings for patients going forward," Goel, a spokesperson for the American Academy of Ophthalmology, told Healthline. "This is a helpful tool for patient education."

Read More: Americans Spend Billions on Vitamins and Supplements That Don't Work »

Cataracts occur when the lens of the eye becomes cloudy due to oxidation over a long period of time.

The researchers said the fluids that bathe the eye are rich in vitamin C, which helps stop the lens from oxidizing.

The dietary intake of vitamin C helps prevent cataracts by increasing the amount of this vitamin in the eye fluid.

The researchers added that smoking and diabetes also are risk factors for certain kinds of cataracts, so a balanced diet and healthy lifestyle are important.

"Healthy diets are always an advantage for patients," added Goel.

Goel also said vitamin C has already been shown to help slow the progression of age-related macular degeneration.

This latest information on cataracts adds to vitamin C's attributes. "It helps overall eye health," he said.

The researchers did note that their observational study has its limitations as it only involved women who were aged 60 years and older.

However, the researchers believe the information could also be relevant for male patients.

Cataracts are the leading cause of blindness in the world, affecting about 20 million people, according to statistics from the World Health Organization (WHO). Cataracts also affect 24 million Americans over the age of 40.

The condition can cause blurry vision, glare, poor night vision, and sensitivity to light.

Initially, better lighting and glasses may help ease some of the symptoms, but as cataracts progress surgery is sometimes needed.

Read More: Diabetes and Blurry Vision: What You Need to Know »

Vitamin C Weight Loss

Source: https://www.healthline.com/health-news/vitamin-c-may-reduce-risk-of-cataracts

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Best Vitamin B12 Supplement Uk / Top 10 Rda Vitamin B12 Uk - Your Best Life - I've decided to produce a short blog post this week on the types of supplements containing b12.

Best Vitamin B12 Supplement Uk / Top 10 Rda Vitamin B12 Uk - Your Best Life - I've decided to produce a short blog post this week on the types of supplements containing b12.. In this section, we have included the absolute best vitamin b12 supplements available in north america. Find the top products of 2021 with our buying guides, based on hundreds of reviews! Symptoms of deficiency include anemia, fatigue, nervous system changes, and cognitive decline. Our official guide to the best vitamin b12 supplements. Vitamin b12 supplements are meant for those looking to replenish their vitamin b12 levels or those who don't get enough of this vitamin through their diet.

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Zenwise health's vitamin b12 supplement provides a strong but not outrageously high dosage. Because vitamin b12 contains the mineral cobalt, compounds with vitamin b12 activity are collectively called cobalamins 1. Vitamin b12 — also known as cobalamin — is an essential vitamin needed for optimal health. Methylcobalamin is the best form of vitamin b12! Vitamin b12 is one of the 13 essential vitamins your body needs to maintain health, growth, and vitality. Vitamin b12 is most prominent in animal based sources like meat, eggs and dairy. Buying guide for best b12 supplements. This vitamin supplement contains b12, biotin, folic acid and vitamin c with other nutrients.

10 best b12 supplements of july 2021.

Best vegetarian vitamin b12 supplement. Our official guide to the best vitamin b12 supplements. Which active ingredients are best? Nu u nutrition made these vitamin b12 supplements with maximum potency and increased absorption. Most vitamin b12 supplements contain cyanocobalamin, which. See our picks for the best 10 b12 supplements in uk. Methylcobalamin is the best form of vitamin b12! Vitamin b12 is required for the proper function and development of the brain, nerves, blood cells the shot works best in people with severe vitamin b12 deficiency and in those not able to take vitamin b12 taking b vitamin supplements that include vitamin b12 might slightly reduce stroke risk in. Zenwise health's vitamin b12 supplement provides a strong but not outrageously high dosage. Vitamin b12 has several names — cyanocobalamin, hydroxocobalamin, cobalamin or methylcobalamin. However, if you struggle to eat the right foods or are deficient, it may be necessary to use a. Outside of supplementing for otherwise deficient intake, vitamin b12 is often taken. Vitamin b12 is an essential vitamin that the body needs to support cognitive functioning, energy production, mental and cardiovascular health.

Make red blood cells and keeping the nervous system healthy. Find the top products of 2021 with our buying guides, based on hundreds of reviews! Best vegetarian vitamin b12 supplement. Outside of supplementing for otherwise deficient intake, vitamin b12 is often taken. It doesn't have the independent lab testing that other supplements have, and its delivery mechanism.

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Look through our top 10 list of the most effective products to help you make the best decision. Best vitamin b12 supplements uk. Methylcobalamin is better absorbed and retained than other forms of vitamin b12 such as cyanocobalamin. Vitamin b12 is an essential nutrient that you can get from foods like meat, fish, eggs and dairy products. Find the top 100 most popular items in amazon health & personal care best sellers. This vitamin is also necessary for the proper functioning of our hearts. Outside of supplementing for otherwise deficient intake, vitamin b12 is often taken. As you know, vitamin b12 is a water soluble vitamin.

Vitamin b12 also called cobalamins is.

Symptoms of deficiency include anemia, fatigue, nervous system changes, and cognitive decline. Zenwise health's vitamin b12 supplement provides a strong but not outrageously high dosage. It could be vitamin b12 deficiency. Vitamin b12 is essential for proper red blood cell production, neurological and cognitive function, and dna synthesis. Because vitamin b12 contains the mineral cobalt, compounds with vitamin b12 activity are collectively called cobalamins 1. However, if you struggle to eat the right foods or are deficient, it may be necessary to use a. Our official guide to the best vitamin b12 supplements. See our picks for the best 10 b12 supplements in uk. Make red blood cells and keeping the nervous system healthy. 112m consumers helped this year. Looking for the best vitamin b12 supplements? Vitamin b12 has several names — cyanocobalamin, hydroxocobalamin, cobalamin or methylcobalamin. There are 4 supplemental forms of vitamin b12 which i discuss in this post.

Vitamin b12 is an essential nutrient that you can get from foods like meat, fish, eggs and dairy products. Jarrows b12 methylcobalamin does not require conversion in the liver to be biologically active. Find the top 100 most popular items in amazon health & personal care best sellers. Nu u nutrition made these vitamin b12 supplements with maximum potency and increased absorption. How to find the best vitamin b12 supplement.

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Vitamin b12 is involved in helping the body: Like all b vitamins, b12 is utilized in enzyme. However, if you struggle to eat the right foods or are deficient, it may be necessary to use a. This post features the five best b12 supplement brands available on the market today. Find the top 100 most popular items in amazon health & personal care best sellers. Discover the best vitamin b12 supplements in best sellers. Zenwise health's vitamin b12 supplement provides a strong but not outrageously high dosage. Because vitamin b12 contains the mineral cobalt, compounds with vitamin b12 activity are collectively called cobalamins 1.

Make red blood cells and keeping the nervous system healthy.

Best vitamin b12 supplement reviews. This vitamin is also necessary for the proper functioning of our hearts. Vitamin b12 is essential for proper red blood cell production, neurological and cognitive function, and dna synthesis. Look through our top 10 list of the most effective products to help you make the best decision. Vitamin b12 has several names — cyanocobalamin, hydroxocobalamin, cobalamin or methylcobalamin. The best way to get enough is to eat a varied and balanced diet; In the late 1940s, it was identified as the substance in. See our picks for the best 10 b12 supplements in uk. Vitamin b12 is an important micronutrient that supports numerous processes within your body. Methylcobalamin is better absorbed and retained than other forms of vitamin b12 such as cyanocobalamin. Methylcobalamin is the best form of vitamin b12! Best vitamin b12 supplements uk. 2021's 10 best vitamin b12 (cobalamin) top supplements.

Symptoms of deficiency include anemia, fatigue, nervous system changes, and cognitive decline best vitamin b12 supplement. Discover the best vitamin b12 supplements in best sellers.

Source: cureline.co.uk

Although this vitamin b12 is plentiful in most people's diets, after the age of 50 some people have vitamin b12 is known as cobalamin and it is the most recent vitamin that has been discovered. Find the top products of 2021 with our buying guides, based on hundreds of reviews! It doesn't have the independent lab testing that other supplements have, and its delivery mechanism. However, if you struggle to eat the right foods or are deficient, it may be necessary to use a. You should be able to get all the vitamin b12 you need by eating a varied and balanced diet.

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There are so many different vitamin b12 supplements on the market that it can be overwhelming to find the best option. Methylcobalamin is the best form of vitamin b12! This vitamin supplement contains b12, biotin, folic acid and vitamin c with other nutrients. Jarrows b12 methylcobalamin does not require conversion in the liver to be biologically active. Best vitamin b12 supplement reviews.

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Best vegetarian vitamin b12 supplement. This vitamin is also necessary for the proper functioning of our hearts. Zenwise health's vitamin b12 supplement provides a strong but not outrageously high dosage. Methylcobalamin is better absorbed and retained than other forms of vitamin b12 such as cyanocobalamin. Furthermore, it is the vitamin responsible for your glowing skin, strong teeth, and great hair.

Source: naturescurezone.com

Vitamin b12 is an essential vitamin that the body needs to support cognitive functioning, energy production, mental and cardiovascular health. Vitamin b12 is one of the 13 essential vitamins your body needs to maintain health, growth, and vitality. Furthermore, it is the vitamin responsible for your glowing skin, strong teeth, and great hair. However, if you struggle to eat the right foods or are deficient, it may be necessary to use a. Vitamin b12 also called cobalamins is.

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However, if you struggle to eat the right foods or are deficient, it may be necessary to use a. Methylcobalamin is better absorbed and retained than other forms of vitamin b12 such as cyanocobalamin. You can also get more info by jumping to our. We hope this selection will help you. Free uk economy delivery online.

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This means that it doesn't stay in the body for a long period of time and that more frequent dosing several of our customer ask us, how to choose best vitamin b12 supplements to recover from deficiency. In this post, we are going to take a look at what vitamin b12 is, why you may be lacking this elusive vitamin and why you should be taking the best b12 supplement on the market. 10 best b12 supplements of july 2021. We hope this selection will help you. In this section, we have included the absolute best vitamin b12 supplements available in north america.

Source: 20twentyliving.com

If you take vitamin b12 supplements, do not take too much as. Free uk economy delivery online. See our picks for the best 10 b12 supplements in uk. Look through our top 10 list of the most effective products to help you make the best decision. Like all b vitamins, b12 is utilized in enzyme.

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Furthermore, it is the vitamin responsible for your glowing skin, strong teeth, and great hair. Vitamin b12 supplements are meant for those looking to replenish their vitamin b12 levels or those who don't get enough of this vitamin through their diet. Symptoms of deficiency include anemia, fatigue, nervous system changes, and cognitive decline. Like all b vitamins, b12 is utilized in enzyme. This vitamin is also necessary for the proper functioning of our hearts.

Source: www.arcturusclinic.co.uk

Outside of supplementing for otherwise deficient intake, vitamin b12 is often taken. Symptoms of deficiency include anemia, fatigue, nervous system changes, and cognitive decline. We hope this selection will help you. The common method for a supplement company to manufacture this. Vitamin b12 supplements that could help hair from going grey.

Source: dominatedepression.com

Because vitamin b12 is water soluble (meaning it dissolves in water if you do require a vitamin b12 supplement, follow this advice from our experts:

Source: www.biovea.com

If you take vitamin b12 supplements, do not take too much as.

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Supplements offer an array of health benefits and due to many not receiving enough vitamins and minerals from food, sometimes it is essential to get the added boost from supplements.

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Vitamin b12 is most prominent in animal based sources like meat, eggs and dairy.

Source: cureline.co.uk

Vitamin b12 is essential for proper red blood cell production, neurological and cognitive function, and dna synthesis.

Source: naturaldispensary.co.uk

See our picks for the best 10 b12 supplements in uk.

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Vitamin b12 is one of the 13 essential vitamins your body needs to maintain health, growth, and vitality.

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Vitamin b12 supplements that could help hair from going grey.

Source: www.seeknatural.co.uk

Vitamin b12 is an essential nutrient that you can get from foods like meat, fish, eggs and dairy products.

Source: i.pinimg.com

Find the top 100 most popular items in amazon health & personal care best sellers.

Source: healthandwellnessreviews.co.uk

Jarrows b12 methylcobalamin does not require conversion in the liver to be biologically active.

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It could be vitamin b12 deficiency.

Source: bigvits.co.uk

Top picks related reviews newsletter.

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Vitamin b12 is essential for proper red blood cell production, neurological and cognitive function, and dna synthesis.

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Outside of supplementing for otherwise deficient intake, vitamin b12 is often taken.

Source: supplementtree.com

If you're looking for the best vitamin b12 supplements to buy this year, then you've come to the right place.

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Vitamin b12 is required for the proper function and development of the brain, nerves, blood cells the shot works best in people with severe vitamin b12 deficiency and in those not able to take vitamin b12 taking b vitamin supplements that include vitamin b12 might slightly reduce stroke risk in.

Source: ws-eu.amazon-adsystem.com

Buying guide for best b12 supplements.

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I've decided to produce a short blog post this week on the types of supplements containing b12.

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Best vitamin b12 supplements uk.

Source: image.makewebeasy.net

Vitamin b12 also called cobalamins is.

Source: healthandwellnessreviews.co.uk

Vitamin b12 is an important micronutrient that supports numerous processes within your body.

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Therefore, it is firstly recommended that followers of vegan and vegetarian diets take a daily vitamin.

Source: healthandwellnessreviews.co.uk

How to find the best vitamin b12 supplement.

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There are so many different vitamin b12 supplements on the market that it can be overwhelming to find the best option.

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