The RDA is the average daily intake that will meet the nutrient requirement of nearly all healthy people in a specific age and gender category. In the past, the RDA of most nutrients represented the levels needed to prevent deficiency diseases such as rickets (lack of vitamin D) or scurvy (lack of vitamin C). Now, an RDA also includes the goal of preventing chronic diseases such as osteoporosis and heart disease, where applicable. The RDA of a nutrient is computed using the Estimated Average Requirement (EAR), which represents the average daily nutrient intake estimated to meet the requirements of half of the healthy individuals in a particular life stage and gender group.

RDAs can differ widely between countries, due to changes in dietary habits, climate and other locally important factors