New guidelines released on vitamin, mineral supplements

By Linda Ciampa
CNN Medical Correspondent

ATLANTA, Georgia (CNN) -- The National Academy of Sciences Institute of Medicine has set an upper limit for how much vitamin A is safe. Several nutritional supplements sold over the Internet or in retail outlets contain 25,000 international units (IU) of vitamin A, but the new report says people should not consume more than 10,000 IU or 3,000 micrograms of vitamin A each day. Too much of the vitamin can lead to liver and nerve damage, bone and joint pain, bone loss and birth defects.

Since 1997, the institute has periodically issued Dietary Reference Intakes (DRI's) for various vitamins and minerals. Tuesday, for the first time since 1989, it released new DRI's for vitamins A and K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium and zinc. DRI's include the Recommended Dietary Allowances or RDA's and upper safe limits for nutrients.

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Dr. Robert Russell discusses vitamin A and carotene Vegeterians need to make sure they get enough carotene WAV sound Colored vegetables are good sources of carotene WAV sound The right amount of carotene and vitamin A WAV sound

In another nutritional development, the so-called B-Carotene factor has been raised. The factor indicates how much beta carotene is needed to make one unit of Vitamin A, explained Dr. Robert Russell, a professor of medicine and nutrition at Tufts University School of Nutrition and chair of the DRI panel for vitamin A. The 1989 bioconversion factor was 6 to 1 -- it was necessary to eat six units of dietary b-carotene for the body to absorb one unit of vitamin A. With the new conversion factor, researchers said a person has to eat 12 units.

"In the United States, vitamin A deficiency is not a problem because we get it from so many sources," said Russell.

Americans get as much as 70 percent of their vitamin A from meat, milk and fish. Other good sources include dark green leafy vegetables, and deep orange or yellow fruits and vegetables. Vegetarians who depend on fruits and vegetables for their vitamin A need to understand that it takes more beta carotene than once believed for the body to convert to vitamin A, added Russell.

Russell explained that vitamin A deficiency is "a very important problem in developing countries such as India and parts of Southeast Asia." Even if it takes twice as much beta carotene in a carrot to provide as much vitamin A as once believed, there's still plenty in most darkly colored fruits and vegetables, said registered dietitian Chris Rosenbloom with the American Dietetic Association.

"A seven-inch carrot contains 2,025 RE's or micrograms of Vitamin A," said Rosenbloom. So, even with the adjustment of the beta carotene conversion factor, one carrot still meets the RDA for vitamin A for men and is more than the RDA for vitamin A for women.

The IOM also released new findings on women and iron. Researchers found that half of pregnant women don't get enough iron during pregnancy. Iron deficiency can lead to premature delivery, spontaneous abortion and infection after delivery.

The institute lowered the RDA for iron for men and post-menopausal women from the 10 milligrams set in 1989 to eight. For pre-menopausal women, the RDA has been raised from 15 to 18 milligrams. For pregnant women, it's been lowered from 30 to 27 milligrams. And for the first time, the IOM set an upper limit of 45 milligrams of iron. Too much iron can result in stomach upset and there is a link, still inconclusive, between heart disease and excess iron.

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