History of the RDAs

When the RDAs were created in 1941, their primary goal was to prevent diseases caused by nutrient deficiencies. They were originally intended to evaluate and plan for the nutritional adequacy of groups, for example, the armed forces and children in school lunch programs, rather than to determine individuals' nutrient needs.

But, because the RDAs were essentially the only nutrient values available, they began to be used in ways other than the intended use. Health professionals often used RDAs to size-up the diets of their individual patients or clients. Statistically speaking, RDAs would prevent deficiency diseases in 97 percent of a population, but there was no scientific basis that RDAs would meet the needs of a single person.

It was evident that the RDAs were not addressing individual needs, and new science needed to be included. Therefore, the Food and Nutrition Board sought to redefine nutrient requirements and develop specific nutrient recommendations for individuals, as well as for groups. Along with these changes, concepts such as tolerable upper intakes and adequate intakes emerged to better meet individuals' needs.

Further, the new RDAs were set with prevention of chronic disease in mind. Sandra Schlicker, Ph.D., Senior Staff Officer with the Food and Nutrition Board explained that the new RDAs will still prevent nutrient deficiencies, but they are now set with an additional purpose. "For the first time, the RDAs are no longer focused only on preventing deficiency diseases such as scurvy or beriberi. Now they are also aimed at reducing the risk of diet-related chronic conditions such as heart disease, diabetes, hypertension and osteoporosis."

How RDAs became DRIs

In 1993, the Food and Nutrition Board put the RDA revision process into motion by holding a symposium and asking for scientific and public comment on how the RDAs should be revised. Utilizing feedback from this conference and other sources, the Food and Nutrition Board developed an ambitious framework for revamping the old RDAs: rather than having a single group of scientists revise the existing set of RDAs, they had expert panels review nutrient categories in much more detail than had ever been done before.

Not only did the definition of RDAs change, but three new values were also created: the Estimated Average Requirement (EAR), the Adequate Intake (AI), and the Tolerable Upper Intake Level (UL). All four values are collectively known as Dietary Reference Intakes or DRIs.

The Food and Nutrition Board partnered with Health Canada, the Canadian government agency responsible for nutrition policy, and the two groups jointly appointed a Dietary Reference Intakes (DRI) Committee. Seven expert panels and two subcommittees assisted the DRI Committee. All members of the DRI Committee, the expert panels and the subcommittees are leaders in their fields of nutrition and food science.

The first report of the DRI Committee was released in 1997 and focused on calcium, vitamin D, phosphorus, magnesium and fluoride. The second report on thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin and choline was released in Spring 1998. Future reports will be published in the next few years. (See timeline for estimated report release dates.)

Extending the RDA Family: Meet the New Members

As a result of the DRI Committee's work to meet individuals' nutrient needs and incorporate current nutrition science, there are now four nutrient requirement values-the RDA, Estimated Average Requirement (EAR), Adequate Intake (AI), and Tolerable Upper Intake Level (UL). The new RDAs are based on Estimated Average Requirements. The Estimated Average Requirement is the amount of a nutrient that will meet the needs of at least 50 percent of healthy people and is typically based on strong research evidence.

However, sometimes an Estimated Average Requirement cannot be accurately determined for a nutrient (e.g., vitamin D, fluoride, pantothenic acid) because the available scientific research is not conclusive. If this is the case, an Adequate Intake is estimated. Although Adequate Intakes are less precise than RDAs, they are still intended to meet or exceed the nutritive needs of nearly all healthy people.

There is more that is new to the nutrient value family. Tolerable Upper Intake Levels for some vitamins and minerals have been established for the first time. The Tolerable Upper Intake Level is the highest amount of a nutrient that can be safely consumed on a daily basis. Past editions of the RDAs have addressed toxicity levels of certain vitamins and minerals but have never clearly defined safe upper intake levels. At this time, Tolerable Upper Intake Levels cannot be established for all nutrients because of incomplete scientific information.

Appropriate Uses of the DRIs

DRIs-the compilation of RDAs, Estimated Average Requirements, Adequate Intakes, and the Tolerable Upper Intake Levels-can be used to evaluate or plan diets for individuals as well as groups. Practitioners who work with individual clients should use the new RDAs and Adequate Intakes as goals for optimal intake. People who eat less than the RDA/Adequate Intakes or exceed the Tolerable Upper Intake Level for a particular nutrient may be at nutritional risk. However, clinical, biochemical and or anthropometric data are required to accurately assess an individual's nutritional status. For groups, the Estimated Average Requirement can be used to set goals for nutrient intake and to measure the prevalence of poor nutrient intake.

To help practitioners and others learn how to use the new DRIs in their work settings, the Food and Nutrition Board appointed a Uses and Interpretations Subcommittee to develop a "user's manual." Committee chair Suzanne Murphy, Ph.D., R.D., Adjunct Associate Professor of Nutrition at the University of California at Davis, believes that the guide will help health professionals, nutrition policy planners, and others use the DRIs to their full advantage. "The process of developing the DRIs has been very thorough and represents a huge step forward for assessing the nutrient requirements of Americans. Now we want to make sure that health professionals and others know how to correctly use these new numbers." Dr. Murphy's goal is that the manual, which will be published within a few years, "be practical and easy to read. We hope that nutrition professionals and policy makers will be able to use it as a first reference before using the DRIs." For More InformationUpdates on the DRI process are available on the National Academy of Sciences web site (www.nas.edu). The site features information about the committee, expert panels and subcommittees. The DRI reports on calcium and the B vitamins can also be accessed. To order copies of the reports, call the National Academy Press at 800-624-6242.

Definitions

Dietary Reference Intakes (DRIs):

The new standards for nutrient recommendations that can be used to plan and assess diets for healthy people. Think of Dietary Reference Intakes as the umbrella term that includes the following values:

Estimated Average Requirement (EAR):

A nutrient intake value that is estimated to meet the requirement of half the healthy individuals in a group. It is used to assess nutritional adequacy of intakes of population groups. In addition, EARs are used to calculate RDAs.

Recommended Dietary Allowance (RDA):

This value is a goal for individuals, and is based upon the EAR. It is the daily dietary intake level that is sufficient to meet the nutrient requirement of 97-98% of all healthy individuals in a group. If an EAR cannot be set, no RDA value can be proposed.

Adequate Intake (AI):

This is used when a RDA cannot be determined. A recommended daily intake level based on an observed or experimentally determined approximation of nutrient intake for a group (or groups) of healthy people.

Tolerable Upper Intake Level (UL):

The highest level of daily nutrient intake that is likely to pose no risks of adverse heath effects to almost all individuals in the general population. As intake increases above the UL, the risk of adverse effects increases.