How Much Vitamin C is Enough?

Taking megadoses of vitamin C is like pouring money down the drain according to research conducted at the National Institutes of Health. Although the current RDA is 60 mg, the researchers found that 200 mg of vitamin C was the level at which the blood was almost fully saturated with the vitamin. Excess vitamin C (over 200 mg) was excreted in the urine. The researchers warned that megadosing with 500 to 1000 mg of vitamin C -- a common practice --could cause kidney stones in some people.

Not all researchers agree with the 200 mg optimal dose. Opponents argue that we still don't have enough information to change the RDA for vitamin C, even though past studies have indicated that populations consuming plenty of vitamin C appear to be better protected from heart disease and cancer. Other aspects of their lifestyles, such as exercise habits and phytochemicals ("plant chemicals") in fruits and vegetables, may be contributing to the health-promoting effects.

If everyone ate 5-a-Day, we would easily surpass the current RDA -- and also benefit from the phytochemicals they contain. For instance, the vitamin C total from a menu including 5-a-Day, such as 6 ounces orange juice, ½ cup spaghetti sauce, 1 kiwi fruit, ½ cup cooked broccoli and 1 medium baked potato, is 223 mg.

Source: Tufts University Diet & Nutrition Letter, October 1996. As abstracted and printed in Lab to Kitchen, Newsletter from ND State University Extension Service. April, 1997.

Mary P Clarke, Ph.D.
Extension Specialist, Nutrition Education

5/97 FILE: NUTRITION, NORMAL/General

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