The Recommended Dietary Allowance (RDA) is a foundational term in nutrition, representing the average daily dietary intake level of a nutrient considered sufficient to meet the requirements of nearly all healthy people. Set by expert panels, the RDA serves as a goal for individuals to ensure they consume enough of a nutrient to maintain health and prevent deficiency diseases. This value is tailored to different life stage and gender groups, recognizing that nutrient needs change throughout a person’s life.
The Framework of Dietary Reference Intakes
The RDA is one component within a broader collection of nutrient intake values known as the Dietary Reference Intakes (DRIs). These comprehensive reference values are used in both the United States and Canada to plan and assess the nutrient intakes of healthy individuals and populations. The DRI framework was established by the Food and Nutrition Board of the National Academy of Medicine to update the original Recommended Dietary Allowances used since the 1940s. This modern framework includes four primary reference values, allowing for a nuanced approach to dietary recommendations that addresses both deficiency prevention and the avoidance of excessive intake.
Recommended Dietary Allowance and Related Values
The Dietary Reference Intakes include three distinct values focused on ensuring nutritional adequacy. The Estimated Average Requirement (EAR) is the starting point for setting most recommendations, representing the daily intake level estimated to meet the requirement of half (50%) of the healthy individuals in a specified group. This value is based on a specific criterion of nutritional adequacy, such as maintaining a particular level of a nutrient in the blood.
The Recommended Dietary Allowance (RDA) is mathematically calculated from the EAR by setting the value two standard deviations above the average requirement. This calculation ensures that an intake at the RDA level is sufficient to meet the needs of 97 to 98 percent of healthy people in that life stage and gender group. The RDA is the primary goal for an individual’s daily nutrient intake, providing a wide margin of safety against deficiency.
When there is insufficient scientific evidence to establish an EAR, the Adequate Intake (AI) is used instead. The AI is based on observed estimates of nutrient intake by a group of apparently healthy people who are maintaining an adequate nutritional state. If an RDA is not available for a nutrient, the AI serves as the recommended goal for individual intake.
Tolerable Upper Intake Level
The Tolerable Upper Intake Level (UL) is a separate value that addresses the risk of adverse health effects from overconsumption. The UL is defined as the highest average daily nutrient intake level that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As a safety ceiling, the UL is not a recommended intake level, but rather a maximum to be consistently avoided.
The risk of adverse effects increases as intake rises above the UL. For example, the UL for Vitamin C is 2,000 milligrams per day for adults, as exceeding this level can lead to gastrointestinal disturbances. Similarly, consuming excessive amounts of Vitamin A over time can result in liver damage. The UL is particularly important for individuals who take nutrient supplements, which can easily push total intake past the safe limit.
Using DRIs to Assess Nutritional Adequacy
Individuals can use the RDA or AI as a target for their average daily intake to ensure a nutritionally adequate diet. When reading a nutrition label, the Percent Daily Value (%DV) is a reference point often based on these values. Staying at or above the RDA/AI helps individuals prevent nutrient deficiencies.
Consumers should also use the UL as a guide to avoid excessive nutrient consumption, especially when taking supplements. The UL applies to total intake from food, fortified products, and supplements combined. Conversely, the Estimated Average Requirement (EAR) is primarily used by public health experts to assess the nutritional adequacy of large population groups. If a significant portion of a population has an average intake below the EAR, public health initiatives may be needed to improve dietary habits.