Dietary Reference Intake

The Dietary Reference Intake (DRI) is a system of nutrition recommendations from the Institute of Medicine (IOM) of the U.S. National Academy of Sciences. The DRI system is used by both the United States and Canada and is intended for the general public and health professionals. Applications include:


 * Composition of diets for schools, prisons, hospitals or nursing homes
 * Industries developing new food stuffs
 * Healthcare policy makers and public health officials

The DRI was introduced in 1997 in order to broaden the existing guidelines known as Recommended Dietary Allowances (RDAs). The DRI values are not currently used in nutrition labeling, where the older Reference Daily Intakes are still used.

History
The Recommended Dietary Allowance (RDA) was developed during World War II by Lydia J. Roberts, Hazel Stiebeling, and Helen S. Mitchell, all part of a committee established by the United States National Academy of Sciences in order to investigate issues of nutrition that might "affect national defense" (Nestle, 35). The committee was renamed the Food and Nutrition Board in 1941, after which they began to deliberate on a set of recommendations of a standard daily allowance for each type of nutrient. The standards would be used for nutrition recommendations for the armed forces, for civilians, and for overseas population who might need food relief. Roberts, Stiebeling, and Mitchell surveyed all available data, created a tentative set of allowances for "energy and eight nutrients", and submitted them to experts for review (Nestle, 35). The final set of guidelines, called RDAs for Recommended Dietary Allowances, were accepted in 1941. The allowances were meant to provide superior nutrition for civilians and military personnel, so they included a "margin of safety." Because of food rationing during the war, the food guides created by government agencies to direct citizens' nutritional intake also took food availability into account.

The Food and Nutrition Board subsequently revised the RDAs every five to ten years. In the early 1950s, United States Department of Agriculture nutritionists made a new set of guidelines that also included the number of servings of each food group in order to make it easier for people to receive their RDAs of each nutrient.

Current recommendations
The current Dietary Reference Intake recommendation is composed of:


 * Estimated Average Requirements (EAR), expected to satisfy the needs of 50% of the people in that age group based on a review of the scientific literature.
 * Recommended Dietary Allowances (RDA), the daily dietary intake level of a nutrient considered sufficient by the Food and Nutrition Board to meet the requirements of 97.5% of healthy individuals in each life-stage and sex group. It is calculated based on the EAR and is usually approximately 20% higher than the EAR (See Calculating the RDA).
 * Adequate Intake (AI), where no RDA has been established, but the amount established is somewhat less firmly believed to be adequate for everyone in the demographic group.
 * Tolerable upper intake levels (UL), to caution against excessive intake of nutrients (like vitamin A) that can be harmful in large amounts. This is the highest level of daily consumption that current data have shown to cause no side effects in humans when used indefinitely without medical supervision.

The RDA is used to determine the Recommended Daily Value (RDV) which is printed on food labels in the U.S. and Canada.

Vitamins and minerals
EARs, RDA/AIs and ULs for an average healthy 44-year old male are shown below. EARs shown as "NE" have not yet been established or not yet evaluated. ULs shown as "ND" could not be determined, and it is recommended that intake from these nutrients be from food only, to prevent adverse effects. Amounts and "ND" status for other age and gender groups, pregnant women, lactating women, and breastfeeding infants may be much different.

EAR: Estimated Average Requirements; RDA: Recommended Dietary Allowances; AI: Adequate Intake; UL: Tolerable upper intake levels.
 * a The UL for magnesium represents extra intake from dietary supplements. High doses of magnesium from dietary supplements or medications often result in diarrhea that can be accompanied by nausea and abdominal cramping. There is no evidence of adverse effects from the consumption of naturally occurring magnesium in foods.

It is also recommended that the following substances not be added to food or dietary supplements. Research has been conducted into adverse effects, but was not conclusive in many cases:

Macronutrients
RDA/AI is shown below for males and females aged 40–50 years.


 * b Includes water from food, beverages, and drinking water.
 * c Based on 0.8 g/kg of body weight

Calculating the RDA
The equations used to calculate the RDA are as follows:

"If the standard deviation (SD) of the EAR is available and the requirement for the nutrient is symmetrically distributed, the RDA is set at two SDs above the EAR:

$$RDA = EAR + 2SD(EAR)$$

If data about variability in requirements are insufficient to calculate an SD, a coefficient of variation (CV) for the EAR of 10 percent is assumed, unless available data indicate a greater variation in requirements. If 10 percent is assumed to be the CV, then twice that amount when added to the EAR is defined as equal to the RDA. The resulting equation for the RDA is then

$$RDA = 1.2EAR$$

This level of intake statistically represents 97.5 percent of the requirements of the population."

Recent developments
In September 2007, the Institute of Medicine held a workshop entitled “The Development of DRIs 1994–2004: Lessons Learned and New Challenges.” At that meeting, several speakers stated that the current Dietary Recommended Intakes (DRI’s) were largely based upon the very lowest rank in the quality of evidence pyramid, that is, opinion, rather than the highest level – randomized controlled clinical trials. Speakers called for a higher standard of evidence to be utilized when making dietary recommendations.