Dietary Reference Intakes suggest nutrient levels for "optimizing health" -- IoM report.

NUTRIENT INTAKE VALUES FOR "OPTIMIZING HEALTH" ESTABLISHED BY IoM in the "Dietary Reference Intakes" report released Aug. 13. Authored by the eight-member Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, a panel of the Institute of Medicine Food & Nutrition Board, the report sets forth DRIs for calcium, phosphorus, magnesium, vitamin D and fluoride, replacing FNB's periodically revised Recommended Dietary Allowances for the nutrients. The DRI report provides for the first time one set of reference values for the U.S. and Canada.

DRIs for six other nutrient groups will follow as funding is available; all will be complete, IoM says, by 2000. The additional DRIs will include: folate and B vitamins; antioxidants (vitamins C, E and selenium); macronutrients (protein, fat and carbohydrates); trace elements (iron and zinc); electrolytes and water; and other food components.

"Unlike the RDAs, which established the minimal amounts of nutrients needed to be protective against possible nutrient deficiency, the new values are designed to reflect the latest understanding about nutrient requirements based on optimizing health in individuals and groups," IoM states.

"Where the scientific evidence allowed," the standing committee "made recommendations aimed at helping individuals at different stages of life obtain enough of a nutrient to promote bone strength and to maintain normal nutritional status," IoM states. The committee's work was funded by the U.S. Department of Agriculture, the National Heart, Lung & Blood Institute and FDA, "with assistance" from Health Canada. Chaired by Vernon Young, PhD, Massachusetts Institute of Technology, the committee worked in collaboration with FNB's 10-member Panel on Calcium and Related Nutrients and 11-member Subcommittee on Upper Reference Levels of Nutrients.

The committee's work began last summer, when the Calcium & Related Nutrients panel met to gather input on considerations for establishing new intake levels ("The Tan Sheet" June 10, 1996, p. 11, and July 15, 1996, p. 21). The Subcommittee on Upper Reference Levels of Nutrients subsequently met to discuss a model to establish maximum intake levels for nutrients ("The Tan Sheet" July 22, 1996, p. 14).

Under the DRI system, the RDA is merely one of four categories of intake: the Estimated Average Requirement (EAR) is the intake value "estimated to meet the requirement, as defined by the specified indicator of adequacy, in 50% of the individuals in a life-stage or gender group"; the RDA is based on a calculation of the EAR (generally two standard deviations above the EAR); the Adequate Intake (AI) value is the average nutrient intake "by a defined population or subgroup that appears to sustain a defined nutritional state, such as normal circulating nutrient values or growth"; and the Tolerable Upper Intake Level (UL) is the "maximal level of nutrient intake that is unlikely to pose risks of adverse health effects to almost all individuals in the target group."

The EAR level can be used as a factor for assessing and planning intakes for various age groups, the report says, while the RDA is to be used as a "goal for dietary intake by individuals." In the "absence of definitive data on which to base an EAR and RDA, the AI may be used as a goal for nutrient intake of individuals." Finally, the UL is "not intended to be a recommended level of intake" but instead provides a level that "can, with high probability, be tolerated biologically," the report states. The need for setting UL levels arose from an increase in the practice of food fortification and use of dietary supplements, the document notes.

The UL levels were derived by the committee based on principles of risk assessment. From an evaluation of the data, the committee identified the highest nutrient intake level where no adverse effects are observed (the "no-observed-adverse-effect-level" or NOAEL); if this level could not be established, the "lowest-observed-adverse-effect-level," or LOAEL, was determined. One of these levels then was divided by the "uncertainty factor" -- based on judgments of weaknesses in the data -- to achieve the UL level. A similar process was used by the Council for Responsible Nutrition in its recently published report assessing safe upper limits of nutrient intake ("The Tan Sheet" July 28, p. 12).

"Low energy intakes reported in recent national surveys may mean that it would be unusual to see changes in food habits to the extent necessary to maintain intakes by all individuals at levels recommended in this report," IoM states. Eating fortified foods or consuming nutrient supplements are methods by which people can meet reference intakes, the report adds.

"The major focus of the development of EARs and AIs has been the determination of the most appropriate indicator of adequacy" for the subject nutrients, the IoM report states. However, a "key question...is `adequate for what,'" the report adds. The committee notes that "in many cases, a continuum of benefits can be ascribed to various levels of intake of the same nutrient."

The indicator used for determining calcium intake levels in several populations, including people ages four to eight, nine to 13, 14-18, 19-30 and 51-70, is the level at which "maximal calcium retention" appears to be achieved. This indicator "is targeted toward maximizing bone mineral content and, therefore, potentially reducing the risk of osteoporosis," IoM notes.

For calcium, an Adequate Intake level, rather than an RDA, is the DRI category used by the committee as a daily intake goal. For adults 19 to 30, the daily AI is 1,000 mg (down from the 1,200 mg/day level established for adults 19 to 24 in the former RDA for calcium); for adults 31-50, the AI also is 1,000 mg (up from the 800 mg/day suggested for ages 25-50 in the former RDA); and for those 51-70, the AI is 1,200 mg (up from the 800 mg/day set forth for those 51 and older in the former RDA). The calcium AI for children nine to 18 also is raised, to 1,300 mg daily from the 1,200 mg/day levels for children 11-18 in the former RDA.

CRN, long-time advocates of increased nutrient intake levels, noted Aug. 14 that the report marks the first time "dietary recommendations made to the public have recognized the prevention of chronic disease through nutrition." Regarding IoM's calcium recommendations, CRN commented: "While these recommendations represent a major step forward, in practical terms, it is difficult for many people to consume enough calcium through diet." Calcium supplements "can help fill the gap between normal dietary intakes and optimal levels," the group added.