supplementation does not prevent or slow the progression of age-related cataract. A systematic review reported that low intake and low serum concentration was associated with greater progression of periodontal disease. Vitamin C is marketed as a topical "serum" ingredient to prevent or treat skin aging, melasma (dark pigment spots) and wrinkles on the face. The purported mechanism is that if functions as an antioxidant, neutralizing free radicals from sunlight exposure, air pollutants or normal metabolic processes. Side effects Vitamin C is a water-soluble vitamin, with dietary excesses not absorbed, and excesses in the blood rapidly excreted in the urine, so it exhibits remarkably low acute toxicity. More than two to three grams may cause indigestion, particularly when taken on an empty stomach. However, taking vitamin C in the form of sodium ascorbate and calcium ascorbate may minimize this effect. Other symptoms reported for large doses include nausea, abdominal cramps and diarrhea. These effects are attributed to the osmotic effect of unabsorbed vitamin C passing through the intestine. In theory, high vitamin C intake may cause excessive absorption of iron. A summary of reviews of supplementation in healthy subjects did not report this problem, but left as untested the possibility that individuals with hereditary hemochromatosis might be adversely affected. There is a longstanding belief among the mainstream medical community that vitamin C increases risk of kidney stones. "Reports of kidney stone formation associated with excess ascorbic acid intake are limited to individuals with renal disease". Reviews state that "data from epidemiological studies do not support an association between excess ascorbic acid intake and kidney stone formation in apparently healthy individuals", although one large, multi-year trial did report a nearly two-fold increase in kidney stones in men who regularly consumed a vitamin C supplement. Diet Recommended levels Recommendations for vitamin C intake by adults have been set by various national agencies: 40 milligrams per day: India National Institute of Nutrition, Hyderabad 45 milligrams per day or 300 milligrams per week: the World Health Organization 80 milligrams per day: the European Commission Council on nutrition labeling 90 mg/day (males) and 75 mg/day (females): Health Canada 2007 90 mg/day (males) and 75 mg/day (females): United States National Academy of Sciences. 100 milligrams per day: Japan National Institute of Health and Nutrition. 110 mg/day (males) and 95 mg/day (females): European Food Safety Authority In 2000, the chapter on Vitamin C in the North American Dietary