DIETARY REFERENCE STANDARDS
The Food and Nutrition Board of the Institute of Medicine (IOM) has been developing reference stan-dards for vitamins and other nutrients called Dietary.
Reference Intakes (DRIs). In the past, the recommended dietary allowances (RDAs), which are the levels of in-take of essential nutrients that are considered to be ade-quate to meet the known nutritional needs of practically all healthy persons, were the primary reference value for vitamins and other nutrients. The DRIs also include other reference values, such as the estimated average re-quirement (EAR) and the adequate intake (AI). The RDA, EAR, and AI reference standards define nutri-tional intake adequacy. Since these recommendations are given for healthy populations in general and not for indi-viduals, special problems, such as premature birth, inher-ited metabolic disorders, infections, chronic disease, and use of medications, are not covered by the requirements. Separate RDAs have been developed for pregnant and lactating women. Vitamin supplementation may be re-quired by patients with special conditions and for those who do not consume an appropriate diet.
A varied diet containing a wide range of foodstuffs provides adequate intake of vitamins for most people, and supplementing these amounts will have no benefi-cial effect and may result in the toxicity associated with hypervitaminosis. The DRI also includes the tolerable upper intake level (UL) of vitamins. The UL is defined as the highest level of intake of a nutrient that will not pose a risk of adverse health effects to most individuals in the general population. The UL is an important ref-erence standard, especially with the current promotion and wide availability of vitamin preparations.