BETHESDA, MARYLAND. The Food and Nutrition Board of the US National Academy of Sciences recently issued new Recommended Dietary Allowances (RDAs) for vitamin-C. The RDA for men and women (USA and Canada) is now 90 mg/day and 75 mg/day respectively. In Germany, Switzerland, Austria, and Japan the RDA is now 100 mg/day for both men and women and in France it is 110 mg/day for both. The RDA for women in the USA was not actually determined by experiment (as it was for men), but was merely based on the difference in average body weight between the two sexes.
Researchers at the National Institutes of Health now recommend that the RDA for healthy young women be increased to 90 mg/day. This recommendation follows a comprehensive depletion/repletion study involving 15 healthy young women who were hospitalized for six months in a dietary ward. The researchers found that vitamin C concentrations in blood plasma, lymphocytes, platelets, monocytes, and neutrophils tended to stabilize at vitamin C intakes of 100 mg/day (50 mg taken twice daily at least two hours before breakfast and dinner). Plasma and circulating cells become saturated at daily vitamin C intakes of 400 mg/day. Higher dosages resulted in increased excretion in the urine. The researchers emphasize that their findings only apply to healthy young women and that optimum vitamin C intakes could be quite different for patients with diabetes, hypertension, high cholesterol levels, kidney failure or heart disease.
Levine, Mark, et al. A new recommended dietary allowance for vitamin C for healthy young women. Proceedings of the National Academy of Sciences, Vol. 98, No. 17, August 14, 2001, pp. 9842- 46