NASEM Requirement Definitions

Estimated average requirement (EAR) : This is the nutrient amount needed to meet the requirement in half the healthy individuals in a particular life stage and gender group. This is the most robust requirement value, because it is based on many studies that determined variation in nutrient intake.

Recommend dietary allowance (RDA): This requirement accounts for a greater proportion of the population in meeting the nutrient needs for nearly all healthy individuals in a particular life stage and gender group. It is defined as the EAR + 2 standard deviations; if EAR variation is unknown, then RDA = EAR × 1.2.

Adequate intake (AI): Average daily nutrient intake that should meet or exceed requirements of specific groups. This value is determined by a panel of experts interpreting limited experimental data. Nutrients defined by this value have limited experimental data with high variation, and the EAR or RDA cannot be determined.

Tolerable upper intake level (UL) : Highest average daily nutrient intake that is not likely to pose an adverse health risk to nearly all individuals in a population. This value is similar to the maximum tolerable level (MTL). Maximum tolerable level is defined as the highest dietary amount of a mineral that can be fed for a brief (up to 3 months) period without causing toxicosis.