Vitamin C

What does it do? Vitamin C is a water-soluble vitamin that has a number of biological functions. Acting as an antioxidant, one of vitamin C’s important functions is to protect LDL cholesterol from oxidative damage. (Only when LDL is damaged does cholesterol appear to lead to heart disease, and vitamin C may be one of the most important antioxidant protectors of LDL.)¹ Vitamin C may also protect against heart disease by reducing the stiffness of arteries and the tendency of platelets to clump together.²

The antioxidant properties of vitamin C are thought to protect smokers, as well as people exposed to secondhand smoke, from the harmful effects of free radicals. A controlled trial demonstrated the ability of 3 grams of vitamin C, taken by non-smokers two hours prior to being exposed to cigarette smoke, to reduce the free radical damage and LDL cholesterol oxidation associated with exposure to cigarette smoke.³ The smoke-induced decline in total antioxidant defense was also diminished. These beneficial effects were not observed in non-smokers under normal conditions (no free radical exposure).

Vitamin C is needed to make collagen, the “glue” that strengthens many parts of the body, such as muscles and blood vessels. Vitamin C also plays important roles in wound healing and as a natural antihistamine. This vitamin also aids in the formation of liver bile and helps to fight viruses and to detoxify alcohol and other substances.

Recently, researchers have shown that vitamin C improves nitric oxide activity.⁴ Nitric oxide is needed for the dilation of blood vessels, potentially important in lowering blood pressure and preventing spasms of arteries in the heart that might otherwise lead to heart attacks. Vitamin C has reversed dysfunction of cells lining blood vessels.⁵ The normalization of the functioning of these cells may be linked to prevention of heart disease.

Evidence indicates that vitamin C levels in the eye decrease with age⁶ and that supplementing with vitamin C prevents this decrease,⁷ possibly leading to a lower risk of developing cataracts.⁸ ⁹ Healthy people have been reported in some, but not all, studies¹⁰ to be more likely to take vitamin C and vitamin E supplements than are people with cataracts.¹¹

Vitamin C has been reported to reduce activity of the enzyme, aldose reductase, in people.¹² Aldose reductase is the enzyme responsible for accumulation of sorbitol in eyes, nerves, and kidneys of people with diabetes. This accumulation is believed to be responsible for deterioration of these parts of the body associated with diabetes. Therefore, interference with the activity of aldose reductase theoretically helps protect people with diabetes.

Vitamin C may help protect the body against accumulation or retention of the toxic mineral, lead. In one preliminary study, people with higher blood levels of vitamin C had much lower risk of having excessive blood levels of lead.¹³ In a controlled trial, male smokers with moderate to high levels of lead received supplements of 1,000 mg per day of vitamin C, 200 mg per day of vitamin C, or a placebo.¹⁴ Only those people taking 1,000 mg per day of vitamin C experienced a drop in the blood lead levels, but the reduction in this group was dramatic.

People with recurrent boils (furunculosis) may have defects in white blood cell function that are correctable with vitamin C supplementation. A preliminary study of people with recurrent boils and defective white blood cell function, found that 1 gram of vitamin C taken daily for four to six weeks, resulted in normalization of white blood cell function.¹⁵ Ten of twelve people receiving vitamin C became symptom-free within one month and remained so for periods of one to three years without additional supplementation. The other two people required long-term vitamin C supplementation to prevent recurrences.

A double-blind trial found that 500 mg of vitamin C per day for one year reduced the risk of developing reflex sympathetic dystrophy (a painful nerve condition of the extremities), after a wrist fracture.¹⁶

In a small, preliminary trial, vitamin C (500 mg twice daily) combined with rutoside (500 mg twice daily), a derivative of the flavonoid, rutin, produced marked improvement in three women with progressive pigmented purpura (PPP), a mild skin condition.¹⁷ Although not a serious medical condition, cosmetic concerns lead people with PPP to seek treatment with a variety of drugs. The vitamin C/rutoside combination represents a promising, non-toxic alternative to these drug treatments, but larger, controlled trials are needed to confirm these preliminary results.

Vitamin C has been used in connection with the following conditions (refer to the individual health concern for complete information):

Rating	Health Concerns
	Anemia (if deficient) Athletic performance (if deficient, or to reduce pain and speed up muscle strength recovery after intense exercise) Bronchitis Bruising (for deficiency) Burns (in combination with vitamin E for prevention of sunburn only) Capillary fragility Common cold/sore throat Gingivitis (periodontal disease) (for deficiency only) Glaucoma Heart attack (for deficiency) High cholesterol (protection of LDL cholesterol) Infection Infertility (male) (for sperm agglutination) Reflex sympathetic dystrophy (prevention) Scurvy Wound healing
	Asthma Atherosclerosis Athletic performance (for exercise recovery) Autism Cataracts Childhood intelligence (for deficiency) Cold sores Diabetes Dysmenorrhea (plus vitamin B3 [niacin] and rutin) Gastritis Gingivitis (periodontal disease) (in combination with flavonoids) Immune function Influenza Iron-deficiency anemia (as an adjunct to supplemental iron) Lead toxicity Pancreatic insufficiency Pre- and post-surgery health (if deficient) Preeclampsia (in combination with vitamin E; for high risk only) Schizophrenia Skin ulcers Sprains and strains
	Age-related cognitive decline Alcohol withdrawal support Amenorrhea Anemia (for thalassemia if deficient) Bipolar disorder/manic depression Boils (recurrent furunculosis) Childhood diseases Chronic obstructive pulmonary disease (COPD) Colon cancer (reduces risk) Diabetic retinopathy (in combination with selenium, vitamin A, and vitamin E) Ear infections (recurrent) Eczema Gallstones Gout Halitosis (if gum disease and deficient) Hay fever Heart attack (for those not deficient) Hepatitis High blood pressure HIV support (oral and topical) Hives Hypoglycemia Leukoplakia Low back pain Macular degeneration Menopause Menorrhagia (heavy menstruation) Morning sickness Parkinson’s disease (in combination with Vitamin E) Peptic ulcer Progressive pigmented purpura (in combination with rutoside) Prostatitis (acute bacterial prostatitis, chronic bacterial prostatitis) Retinopathy (in combination with selenium, vitamin A and vitamin E) Sickle cell anemia Sinusitis Tardive dyskinesia Urinary tract infection Vitiligo
Reliable and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit. An herb is primarily supported by traditional use, or the herb or supplement has little scientific support and/or minimal health benefit.

How much is usually taken? The recommended dietary allowance (RDA) for vitamin C in nonsmoking adults is 75 mg per day for women and 90 mg per day for men. For smokers, the RDAs are 110 mg per day for women and 125 mg per day for men. Most clinical vitamin C studies have investigated the effects of a broad range of higher vitamin C intakes (100–1,000 mg per day or more), often not looking for (or finding) the “optimal” intake within that range. In terms of heart disease prevention, as little as 100–200 mg of vitamin C appears to be adequate.²¹ Although some doctors recommend 500–1,000 mg per day or more, additional research is needed to determine whether these larger amounts are necessary. Some vitamin C experts propose that adequate intake be considered 200 mg per day because of evidence that the cells of the human body do not take up any more vitamin C when larger daily amounts are used.²²

Some scientists have recommended that healthy people take multi-gram amounts of vitamin C for the prevention of illness. However, little or no research supports this point of view and it remains controversial. Supplementing more results in an excretion level virtually identical to intake, meaning that consuming more vitamin C does not increase the amount that remains in the body.²³ On the basis of extensive analysis of published vitamin C studies, researchers at the Linus Pauling Institute at Oregon State University have called for the RDA to be increased, but only to 120 mg.²⁴ This same report reveals that “. . . 90–100 mg vitamin C per day is required for optimum reduction of chronic disease risk in nonsmoking men and women.” Thus, the multiple gram amounts of vitamin C taken by many healthy people may be superfluous.

The studies that ascertained approximately 120–200 mg daily of vitamin C is correct for prevention purposes in healthy people have typically not investigated whether people suffering from various diseases can benefit from larger amounts. In the case of the common cold, a review of published trials found that amounts of 2 grams per day in children appear to be more effective than 1 gram per day in adults, suggesting that large intakes of vitamin C may be more effective than smaller amounts, at least for this condition.²⁵

Are there any side effects or interactions? Some people develop diarrhea after as little as a few grams of vitamin C per day, while others are not bothered by ten times this amount. Strong scientific evidence to define and defend an upper tolerable limit for vitamin C is not available. A review of the available research concluded that high intakes (2–4 grams per day) are well-tolerated by healthy people.²⁶ However, intake of large amounts of vitamin C can deplete the body of copper ²⁷ ²⁸ —an essential nutrient. People should be sure to maintain adequate copper intake at higher intakes of vitamin C. Copper is found in many multivitamin-mineral supplements. Vitamin C increases the absorption of iron and should be avoided by people with iron overload diseases (e.g., hemochromatosis, hemosiderosis). Vitamin C helps recycle the antioxidant, vitamin E.

It is widely (and mistakenly) believed that mothers who consume large amounts of vitamin C during pregnancy are at risk of giving birth to an infant with a higher-than-normal requirement for the vitamin. The concern is that the infant could suffer “rebound scurvy,” a vitamin C deficiency caused by not having this increased need met. Even some medical textbooks have subscribed to this theory.²⁹ In fact, however, the concept of “rebound scurvy” in infants is supported by extremely weak evidence.³⁰ Since the publication in 1965 of the report upon which this mistaken notion is based, millions of women have consumed high amounts of vitamin C during pregnancy and not a single new case of rebound scurvy has been reported.³¹

A preliminary study found that people who took 500 mg per day of vitamin C supplements for one year had a greater increase in wall thickness of the carotid arteries (vessels in the neck that supply blood to the brain) than those who did not take vitamin C.³² Thickness of carotid artery walls is an indicator of progression of atherosclerosis. Currently, no evidence supports a cause-and-effect relationship for the outcome reported in this study. The vast preponderance of research suggests either a protective or therapeutic effect of vitamin C for heart disease, or no effect at all.

Are there any drug interactions? Certain medications may interact with vitamin C. Refer to the drug interactions safety check for a list of those medications.

People with the following conditions should consult their doctor before supplementing with vitamin C: glucose-6-phosphate dehydrogenase deficiency, iron overload (hemosiderosis or hemochromatosis), history of kidney stones, or kidney failure.

It has been suggested that people who form calcium oxalate kidney stones should avoid vitamin C supplements, because vitamin C can be converted into oxalate and increase urinary oxalate.³³ ³⁴ Initially, these concerns were questioned because of potential errors in the laboratory measurement of oxalate.³⁵ ³⁶ However, using newer methodology that rules out this problem, recent evidence shows that as little as 1 gram of vitamin C per day can increase the urinary oxalate levels in some people, even those without a history of kidney stones.³⁷ ³⁸ In one case, 8 grams per day of vitamin C led to dramatic increases in urinary oxalate excretion and kidney stone crystal formation causing bloody urine.³⁹ People with a history of kidney stones should consult a doctor before taking large amounts (1 gram or more per day) of supplemental vitamin C.

Despite possible therapeutic effects of vitamin C in people with diabetes at lower intakes, one case of increased blood sugar levels was reported after taking 4.5 grams per day.⁴⁰

References:

1. Balz F. Antioxidant vitamins and heart disease. Presented at the 60th Annual Biology Colloquium, Oregon State University, Corvallis, Oregon, February 25, 1999.

2. Wilkinson IB, Megson IL, MacCallum H, et al. Oral vitamin C reduces arterial stiffness and platelet aggregation in humans. J Cardiovasc Pharmacol 1999;34:690–3.

3. Valkonen MM, Kuusi T. Vitamin C prevents the acute atherogenic effects of passive smoking. Free Radic Biol Med 2000 Feb 1;28:428–36.

4. Taddei S, Virdis A, Ghaidoni L, et al. Vitamin C improves endotheoium-dependent vasodilation by restoring nitric oxide activity in essential hypertension. Circulation 1998;97:2222–9.

5. Chambers JC, McGregor A, Jean-Marie J, et al. Demonstration of rapid onset vascular endothelial dysfunction after hyperhomocysteinemia. An effect reversible with vitamin C therapy. Circulation 1999;99:1156–60.

6. Taylor A. Cataract: relationship between nutrition and oxidation. J Am Coll Nutr 1993;12:138–46 [review].

7. Taylor A, Jacques PF, Nadler D, et al. Relationship in humans between ascorbic acid consumption and levels of total and reduced ascorbic acid in lens, aqueous humor, and plasma. Curr Eye Res 1991;10:751–9.

8. Jacques PF, Chylack LT Jr. Epidemiologic evidence of a role for the antioxidant vitamins and carotenoids in cataract prevention. Am J Clin Nutr 1991;53:352S–5S.

9. Jacques PF, Chylack LT, McGandy RB, Hartz SC. Antioxidant status in persons with and without senile cataract. Arch Ophthalmol 1988;106:337–40.

10. Seddon JM, Christen WG, Manson JE, et al. The use of vitamin supplements and the risk of cataract among US male physicians. Am J Public Health 1994;84:788–92.

11. Robertson JM, Donner AP, Trevithick JR. Vitamin E intake and risk of cataracts in humans. Ann NY Acad Sci 1989;570:372–82.

12. Vincent TE, Mendiratta S, May JM. Inhibition of aldose reductase in human erythrocytes by vitamin C. Diabetes Res Clin Pract 1999;43:1–8.

13. Simon JA, Hudes ES. Relationship of ascorbic acid to blood lead levels. JAMA 1999;281:2289–93.

14. Dawson EB, Evans DR, Harris WA, et al. The effect of ascorbic acid supplementation on the blood lead levels of smokers. J Am Coll Nutr 1999;18:166–70.

15. Levy R, Shriker O, Porath A, et al. Vitamin C for the treatment of recurrent furunculosis in patients with impaired neutrophil functions. J Infect Dis 1996;173:1502–5.

16. Zollinger PE, Tuinebreijer WE, Kreis RW, Breederveld RS. Effect of vitamin C on frequency of reflex sympathetic dystrophy in wrist fractures: a randomised trial. Lancet 1999;354:2025–8.

17. Reinhold U, Seiter S, Ugurel S, Tilgen W. Treatment of progressive pigmented purpura with oral bioflavonoids and ascorbic acid: an open pilot study in 3 patients. J Am Acad Dermatol 1999;41(2 Pt 1):207–8.

18. Kharb S. Total free radical trapping antioxidant potential in pre-eclampsia. Int J Gynaecol Obstet 2000;69:23–6.

19. Simon JA, Hudes ES. Serum ascorbic acid and gallbladder disease prevalence among US adults. Arch Intern Med 2000;160:931–6.

20. Makoff R. Vitamin replacement therapy in renal failure patients. Miner Electrolyte Metab 1999;25:349–51 [review].

21. Balz F. Antioxidant Vitamins and Heart Disease. Presented at the 60th Annual Biology Colloquium, Oregon State University, February 25, 1999.

22. Levine M, Rumsey SC, Daruwala R, et al. Criteria and recommendations for vitamin C intake. JAMA 1999;281:1415–23.

23. Levine M, Conry-Cantilena C, Wang Y, et al. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proc Natl Acad Sci 1996;93:3704–9.

24. 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.

25. Hemilä H. Vitamin C supplementation and common cold symptoms: factors affecting the magnitude of the benefit. Med Hypotheses 1999;52:171–8 [review].

26. Johnston CS. Biomarkers for establishing a tolerable upper intake level for vitamin C. Nutr Rev 1999;57:71–7.

27. Sandstead HH. Copper bioavailability and requirements. Am J Clin Nutr 1982;35:809–14 [review].

28. Finley EB, Cerklewski FL. Influence of ascorbic acid supplementation on copper status in young adult men. Am J Clin Nutr 1983;37:553–6.

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30. Cochrane WA. Overnutrition in prenatal and neonatal life: a problem? Can Med Assoc J 1965;93:893–9.

31. Gaby AR. The myth of rebound scurvy. Townsend Letter for Doctors 2000;June:122.

32. Dwyer J, Nicholson LM, Shircore A, et al. Vitamin C intake and progression of carotid atherosclerosis. The Los Angeles Atherosclerosis Study. American Heart Association Annual Meeting. March 2, 2000 [abstract].

33. Piesse JW. Nutritional factors in calcium containing kidney stones with particular emphasis on vitamin C. Int Clin Nutr Rev 1985;5:110–29 [review].

34. Ringsdorf WM, Cheraskin WM. Medical complications from ascorbic acid: a review and interpretation (part one). J Holistic Med 1984;6:49–63.

35. Hoffer A. Ascorbic acid and kidney stones. Can Med Assoc J 1985;32:320 [letter].

36. Wandzilak TR, D’Andre SD, Davis PA, Williams HE. Effect of high dose vitamin C on urinary oxalate levels. J Urol 1994;151:834–7.

37. Levine M. Vitamin C and optimal health. Presented at the February 25, 1999 60th Annual Biology Colloquium, Oregon State University, Corvallis, Oregon.

38. Levine M, Conry-Cantilena C, Wang Y, et al. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proc Natl Acad Sci 1996;93:3704–9.

39. Auer BL, Auer D, Rodgers AL. Relative hyperoxaluria, crystalluria and haematuria after megadose ingestion of vitamin C. Eur J Clin Invest 1998;28:695–700.

40. Branch DR. High-dose vitamin C supplementation increases plasma glucose. Diabetes Care1999;22:1218 [letter].