Magazine article Drug Topics

Upper Limit and Adequate Intake Levels Set for Nutrients

Magazine article Drug Topics

Upper Limit and Adequate Intake Levels Set for Nutrients

Article excerpt

SELF-CARE

The old adage "everything in moderation" seems to be more apt than ever, at least when it comes to taking vitamin A. So a panel of the National Academy of Sciences' Institute of Medicine (IOM) appears to warn in a new report on Dietary Reference Intakes (DRIs).

In an effort to help people avoid harm from taking too much of a nutrient, the panel has established "upper intake" levels (ULs). It also has recommended what it calls "adequate intake" levels (AI), based on diets known to be nutritionally adequate for the U.S. and Canadian populations when not enough evidence exists to set a Recommended Dietary Allowance (RDA).

The panel set a UL for vitamin A intake for both foods and supplements at 3,000 micrograms a day for adults. Excess vitamin A intake may increase the risk of physical birth defects, liver abnormalities in adults, and bulging of the skull where bone has not yet formed in infants and young children.

To ensure adequate stores of vitamin A in the body, the panel recommended that women should consume 700 micrograms a day and men should take 900 mcg daily.

Vitamin A is essential to maintain normal reproduction, vision, and immune function. It also plays a role in gene expression, embryonic development, and growth. A deficiency of vitamin A, although uncommon in North America, can result in vision impairment, especially night blindness.

Here are some other nutrient levels released in the new guidelines:

* The RDA for iron for adult men and postmenopausal women is 8 milligrams per day and 18 mg/day for premenopausal women. The RDA for pregnant women is 27 mg/day, which usually requires taking a small supplement. The RDA for women who breast-feed and who are not menstruating is 9 mg a day, and for adolescents who breast-feed, it is 10 mg daily. The UL for iron is set at 45 mg per day for adults, above which gastrointestinal distress may occur, especially when iron supplements are consumed on an empty stomach. Research has suggested a possible link between elevated iron stores and a higher incidence of heart disease and cancer.

* The RDA for zinc is set at 8 milligrams per day for women and 11 mg per day for men. A UL of 40 mg for adults was recommended, based on studies showing that zinc adversely affects copper absorption at high levels of intake.

* The panel recommended an AI of 120 micrograms of vitamin K for men and 90 mcg for women (no UL was established). …

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