On the other hand, some people are taking megadoses of vitamin A that could damage the liver or cause birth defects in pregnant women. Generally, the body protects itself from too much vitamin A, but eating too much liver has proved fatal in children.
Besides vitamin A, the board examined the nutritional value of 13 additional vitamins and minerals, and most of the recommendations for minerals were slightly lower than in the past. In one exception, the recommended dose of vitamin K, essential for blood clotting, went up slightly to 120 mcg for men and 90 for women.
For iron, another crucial mineral, the board suggested slightly raising the amount for women and slightly lowering the dose for men. Postmenopausal women and men should get 8 mg a day, while premenopausal women (who lose blood during menstruation) should get 18 mg daily. The panel says pregnant women should get 27 mg daily and establishes an upper limit for adults at 45 mg daily, which is considered safe for all but those with the genetic disease known as hemochromatosis.
For a variety of other vitamins and minerals, the board recommended doses based on the average consumption of American adults. For chromium, for example, they found that harmful side effects are rare from too much chromium in food and based its daily recommendations of 35 mcg for men and 25 mcg for women on average diets.
The RDA for the popular supplement zinc was set at 11 and 8 mg a day for men and women, respectively, with an upper limit of 40 mg. The scientists say that vegetarians may need about 50% more than nonvegetarians, and infants between 7 and 12 months old will not get adequate amounts of zinc from mother's milk and would need to get it from other foods or formula.
- The new RDA for copper is 900 mcg a day for both men and women, with an upper limit of 10 mg a day.
- The new RDA for iodine is 150 mcg a day for both men and women, with an upper limit of 1.1 mg a day.
- The new RDA for manganese is 2.3 mg for men and 1.8 mg for women, daily, with an upper limit of 11 mg a day.
- The new RDA for molybdenum is 45 mcg a day for both men and women, with an upper limit of 2 mg a day.