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and the United States. If the degree of absorption of the nutrient is unusually low on a chronic basis (e.g., because of very high fiber intake), a higher intake may be needed. If the primary source of a B vitamin is a supplement (e.g., B12 for the elderly), a higher percentage of the vitamin may be absorbed and so a smaller intake may be required.

The DRIs apply to the healthy population. RDAs and AIs are levels of intake recommended for individuals. Meeting the recommended intake for the B vitamins and choline would not necessarily be sufficient for individuals who are already malnourished. People with diseases that result in malabsorption syndrome or who are receiving treatments such as hemodialysis or peritoneal dialysis may have increased requirements. Special guidance should be provided for those with greatly increased nutrient requirements. Although the RDA or AI may serve as the basis for such guidance, qualified medical and nutrition personnel should make necessary adaptations for specific situations.

CATEGORIES OF DIETARY REFERENCE INTAKES

Each type of Dietary Reference Intake (DRI) refers to average daily nutrient intake of individuals over time. The amount taken may vary substantially from day to day without ill effect in most cases.

Recommended Dietary Allowance

The Recommended Dietary Allowance (RDA) is the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group (see Figure 1-1). The RDA is intended to be used as a goal for daily intake by individuals. The process for setting the RDA is described below; it depends on being able to set an Estimated Average Requirement (EAR). That is, if an EAR cannot be set, no RDA will be set.

Estimated Average Requirement1

The EAR is the daily intake value that is estimated to meet the requirement—as defined by the specified indicator of adequacy—

1  

The definition of EAR implies a median as opposed to a mean, or average. The median and average would be the same if the distribution of requirements followed a symmetrical distribution and would diverge as a distribution became skewed.



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