April 15, 1996 Two hundred milligrams of vitamin C may be an appropriate daily amount for healthy men, according to a new study by the National Institutes of Health (NIH). The findings are published in the April 16 Proceedings of the National Academy of Sciences.
"Eating five fruits and vegetables a day will easily provide 200 mg," says principal investigator Dr. Mark Levine of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), a part of the NIH.
Seven healthy men aged 20 to 26 years old were hospitalized for 4 to 6 months and fed a vitamin C-restricted diet. Reducing the amount of stored vitamin C in the body ensured accurate measurements of absorption of the nutrient for daily doses ranging from 30 mg to 2,500 mg.
Among Levine's findings: at 30 mg, six patients reported feeling tired and irritable. At 200 mg, plasma had more than 80 percent maximal concentration of vitamin C and tissues were completely saturated. Doses of 500 mg and higher were completely excreted in urine. At 1,000 mg, some volunteers showed potential adverse effects, such as high levels of oxalate and uric acid in the urine, which might lead to kidney stones. "It's almost as if we are programmed to have a certain amount of vitamin C and no more," says Levine.
The study is the first to measure levels of absorption, distribution and excretion of vitamin C for multiple doses in patients who are hospitalized, which ensures accurate dosage and control of diet. Such a rigorous study provides the kind of data needed to establish a Recommended Daily Allowance (RDA). The current RDA for vitamin C, which is determined by the Food and Nutrition Board of the National Research Council, is 60 mg. That value is based on the amount of vitamin C needed to prevent a person from getting scurvy and provide body stores for about 30 days, with a margin of safety.
"It's a great incentive for people to eat more fruits and vegetables," says Dr. Van Hubbard, director of NIDDK's Division of Nutrition Research Coordination. He explains that vitamin C contributes to healing wounds, maintenance of capillaries, bones and teeth, and absorption of iron. Citrus fruits, strawberries, and green vegetables such as broccoli are rich in vitamin C.
"There's another message here for doctors," Levine adds. "They should ask patients who complain of fatigue or irritability what they eat. If their diet is all fast food, they may be deficient in vitamin C. It's a good, cheap intervention to first try adding fruits and vegetables to the diet for a few weeks."
Levine is now studying ideal intake for women. When asked whether he takes supplements, Levine says, "I used to, but now I eat my fruits and vegetables."
Other Resource:
National Research Council, News Office, Mr. Dan Quinn (202) 334-2138
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