The IoM, an arm of the independent National Academies of Science, also revised slightly downward its recommendations for iron, saying men and women past menopause risk accumulating too much in their bodies, which in turn can increase the risk of heart attack. The main worry, it said, is that people may get too much vitamin A and iron from supplements. No one should take in more than 45 milligrams a day, the IoM said. The institute stands by the standard advice that food, and not vitamin pills, is the best source for nearly all vitamins in the diet.
Carotenes are the precursors to vitamin A found in fruits and vegetables.
Organ meats such as liver as also rich in vitamin A, but it is possible to get vitamin A poisoning from too much, Russell said. Too much vitamin A can cause birth defects when taken by pregnant women and can cause potentially fatal liver disease. The IoM slightly raised the recommended intake of vitamin K, found in leafy green vegetables and key to helping blood clot properly. The adequate intake is considered to be 120 micrograms for men and 90 micrograms for women. It said men and women both should get 900 micrograms a day of copper and 150 micrograms of iodine.