The Recommended Dietary Allowance (RDA) is the average daily dietary intake level considered sufficient to meet the nutrient requirements of nearly all healthy individuals. The RDA is specifically set to cover the needs of 97% to 98% of people within a particular life stage and gender group. This value is a target for individuals to ensure nutritional adequacy and prevent deficiency diseases. RDAs are used by nutrition professionals and public health officials to plan and assess diets for healthy populations.
How Recommended Dietary Allowance Values Are Determined
The process for establishing the RDA is based on a statistical model that accounts for the variation in nutrient needs. These standards are developed by the National Academy of Medicine (NAM) as part of the Dietary Reference Intakes (DRIs) system. The calculation begins with the Estimated Average Requirement (EAR), which is the daily intake value estimated to meet the nutrient requirement of only 50% of healthy individuals in a group.
The EAR serves as the median requirement, and the RDA is mathematically derived from this figure to build in a margin of safety. To cover 97% to 98% of the healthy population, the RDA is set by adding two standard deviations (2 SD) of the requirement to the EAR. If the standard deviation is unknown, a coefficient of variation of 10% is typically assumed, resulting in an RDA equal to 1.2 times the EAR.
The ability to calculate an EAR is a prerequisite for setting an RDA. If there is insufficient data to establish the EAR, an RDA cannot be determined for that nutrient.
Differentiating RDA from Other Intake Metrics
The RDA is one of four main metrics, collectively known as the Dietary Reference Intakes (DRIs). The Estimated Average Requirement (EAR) is the starting point for calculating the RDA. The EAR meets the needs of 50% of the group and is primarily used by public health researchers to assess nutrient intakes for groups, not individuals.
When there is not enough scientific evidence to establish an EAR and subsequently an RDA, an Adequate Intake (AI) value is set instead. The AI is based on observed or experimentally determined estimates of nutrient intake by a group of healthy people. While the AI is assumed to ensure nutritional adequacy, it has a more limited evidence base than the RDA.
The Tolerable Upper Intake Level (UL) is the fourth metric, representing the maximum daily intake of a nutrient that is unlikely to pose a risk of adverse health effects to almost all individuals. Unlike the RDA and AI, which are minimum targets to prevent deficiency, the UL is a safety limit to prevent toxicity from excessive intake, particularly relevant for supplement use.
Using RDA for Daily Nutritional Planning
The RDA serves as a practical, actionable target for individuals and is a foundation for national nutrition guidance. It is used in developing food guides and educational materials to help the public make informed choices about their diet. For instance, the RDA is a factor in setting the Daily Value (DV) that appears on food and supplement labels in the United States. The DV is a single reference value for labeling purposes, often based on the highest RDA for a given nutrient across various age and gender categories for adults and children over four.
The RDA is designed for healthy people and may not apply to those with chronic illnesses or medical conditions that alter nutrient metabolism. For these groups, individual nutritional requirements may be higher or lower than the established RDA, necessitating personalized medical advice. The RDA is an average target over several days, not a strict daily requirement, acknowledging that nutrient intake can vary daily.