RDAs, ULs Released for Micronutrients

RDAs, ULs Released for Micronutrients

WASHINGTON--On Jan. 9, a 561-page report suggesting Recommended DietaryAllowances (RDAs) and Tolerable Upper Intake Levels (ULs) for 12 micronutrientshit the news waves. These findings came from a research panel at the NationalAcademy of Sciences' Institute of Medicine's Food & Nutrition Board (FNB),and media bigwigs such as CNN.com, MSNBC.com and the Associated Press (AP) tookpart in spreading the word.

The most newsworthy part of the report included establishing a UL for vitaminA: 3,000 mcg/d (or 10,000 IU) for adults and an RDA of 900 mcg/d for men and 700mcg/d for women. While a lack of vitamin A may cause blindness, excess vitamin Aintake may increase the risk of birth defects and liver problems for adults.Most Americans consume 70 percent of this vitamin from meat, milk, fish, greenleafy vegetables and deep orange or yellow fruits and vegetables.

In addition, the report questioned the "B-Carotene factor." Thefactor relates to how much beta carotene constitutes one unit of vitamin A.According to Robert Russell, a professor of medicine and nutrition at TuftsUniversity School of Nutrition and chair of the FNB panel, reported that in1989, it was found that six units of dietary beta carotene equaled one unit ofabsorbable vitamin A. However, Russell stated the correct amount is 12 units.

Also, the report noted that almost half of all pregnant women may be irondeficient, which may lead to premature delivery, spontaneous abortion and birthdefects. The RDA for iron was set at 27 mg/d for pregnant women, as well as 8mg/d for men and 18 mg/d for premenopausal women. An UL intake was set at 45mg/d; according to the report, some research has suggested that elevated ironstores may lead to a higher risk for heart attacks and cancer.

Recommended levels were also set for vitamin K (90 to 120 mcg/d), chromium(25 to 35 mcg/d), copper (900 mcg/d), iodine (150 mcg/d), molybdenum (45 mcg/d)and zinc (8 to 11 mg/d). The ULs were set for boron (20 mg/d), copper (10,000mcg/d), iodine (40 mg/d), molybdenum (2,000 mcg/d), nickel (1.1 mg/d), vanadium(1.8 mg/d) and zinc (1,100 mcg/d). Rather than an RDA, the panel set an adequateintake (AI) level for manganese of 1.8 to 2.3 mg/d with a ULs of 11 mg/d.Neither an RDA nor a UL were set for arsenic or silicon.

This is the fourth report in a continuing line of research updatingrecommended dietary allowances (RDA), and it follows the April 11, 2000, reporton vitamins C, E and selenium. The FNB's panel on micronutrients based intakelevels on scientific literature from the United States and Canada.

The Council for Responsible Nutrition (CRN) found FNB's report to beconsistent with CRN's 1997 Vitamin and Mineral Safety. However, minordifferences were found between FNB's ULs and CRN's. "One point of concernis the low recommendations for chromium that are based on the usual intakes inapparently healthy people, rather than the clinical trial data from people withimpaired glucose tolerance," said John Hathcock, vice president ofnutritional and regulatory science at CRN.

The FNB researchers concluded that more studies need to be conducted tounderstand the functional and biochemical endpoints of sufficient andinsufficient levels of nutrients, as well as the interactions betweenmicronutrients.

For more information about the FNB report, visit www.iom.edu; for a copy of the NHANES III survey, visit www.cdc.gov/nchs; and for more about CRN, visit www.crnusa.org.