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| The Third National Health and Nutrition Survey, also called NHANES III, showed that 11% of nonsmoking women and 21% of nonsmoking men in the United States do not get enough vitamin C. One of the main objections to mega-dose vitamin C use has been the possibility of developing kidney stones from elevated oxalic acid levels in the urine. More accurate testing methods have shown there are no oxalic acid elevations in vitamin C users. Urinary oxalate excretion generally does not increase significantly for both normal subjects and stone-formers with ascorbic acid supplementation unless doses exceed 6gm daily; however, oxalate excretion even at those high doses is still usually in the range achievable by dietary influences alone. The exceptions derive from anecdotal reports of a small number of cases and from one poorly controlled trial with unstated methodology and questionable assay techniques (Piesse JW. Nutritional factors in calcium-containing kidney stones with particular emphasis on vitamin C.) [Int Clin Nutr Rev 5(3): pp.110-29, 1985] A study did not find a correlation between a high daily intake of vitamin C or vitamin B6 and the risk of stone formation, even when consumed in large doses. Source Most ascorbic acid is synthesized by the oxidation of l-sorbose (usually derived from corn). To get the maximum effect of ascorbic acid supplements, one should combine them with plant flavonoids. The best sources of vitamin C are fruits and vegetables. Acerola is a small cherry-like fruit of the small shrub Malpighia glabra. Acerola also contains such other vitamins as vitamin A, thiamin, riboflavin and niacin in similar proportions as other fruits. However, in some conditions, in order for vitamin C to be effective it has to be used in doses that come very close to causing diarrhea. If you are consuming doses of vitamin C greater than perhaps 500mg per day, do not stop its use abruptly. The RDA for vitamin C is 75mg for women and 90mg men. |