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Glutathione and Vitamin C Defense Systems

Theodore Hersh, MD, MACG
Professor of Medicine, Emeritus, Emory University

Vitamin C accumulates as a free radical unless this ascorbate is reduced by L-glutathione to ascorbic acid. Indeed, various recent studies have documented that high doses of vitamin C are followed by oxidative stress as evidenced by increased levels of markers of lipid peroxidation and damage to DNA.

Podmore and co-workers reported an increased level of a marker of DNA damage in lymphocytes of healthy volunteers taking 500mg vitamin C daily for six weeks. Ascorbate blood levels were also increased. This damage to DNA by vitamin C reflects a potentially mutagenic cellular lesion. (Nature 1998; 392: 559)

Moreover, Nyyssonen found that oral supplementation also of 500 mg vitamin C daily for two months alone without any other antioxidant in smoking men promoted oxidative stress as evidenced by increased levels in markers of lipid peroxidation. (Eur J Clin Nutr 1997; 51: 154-163) Other studies using single dose Beta Carotene, which also accumulates as a free radical revealed an increase in cancer and cardiovascular disease in individuals who are already at high risk, such as smokers (Hennekens, C.H. et al NEJM 1996; 334: 1145-1149)

Experiments in hamster buccal mucosa have shown that vitamin C applied topically enhances the development of carcinomas in the buccal mucosa. (Schwartz, J et al, Oral Surg Med Pathol 1993; 76: 718-722)

In a study on the use of antioxidants to improve photoprotection in human skin, Steenvoorden and Van Henegouwen reported the best results they obtained on avoidance of UV damage were with the use of synergistic antioxidants. They showed too that “too much” of a single component like vitamin C could have deleterious effects accelerating photoaging.

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