Explain the Recommended Dietary Allowances - Nutrition?

The recommended dietary allowances are defined as the 'daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all healthy individuals in a particular life stage and gender group'. The RDA is derived from the statistical distribution of requirements for nutrients. It is generally assumed that nutrient requirements are distributed normally. With this kind of distribution the requirements of 97 to 98% of individuals in a given population group will be below the mean plus two standard deviations. Thus, mean + 2 SD will cover the requirements of practically all individuals in that population group and is designated as the RDA for that particular nutrient. This approach is used for deriving the RDA for all nutrients except energy. The RDA is intended for use primarily as a goal for usual intakes. Recommended Nutrient Intakes (RNIs) is another term commonly used to describe nutrient requirements and is equivalent to RDA.