The RDA and DRI

Early recommendations for nutrient intakes date back to the mid-1800s when, in the Lancashire district in England, nutrient intake recommendations were established because of a famine. The purpose, however, was solely to ensure adequate minimal nutrient intakes for the population and the army. In 1941, the U.S. National Research Council first issued recommendations which had the goal of achieving "perfect health" in the population. These Recommended Dietary Allowances (RDA) were updated in five-year cycles. In order to determine the RDA for a specific nutrient, its intake is determined in a representative sample population with no deficiency symptoms. The RDA are derived from the resulting Estimated Average Requirements (EAR). Where no or insufficient scientific data are available, an Adequate Intake (AI) is approximated. No RDA and consequently no Dietary Reference Intakes (DRI) are set for these nutrients. The Energy RDA (for energy nutrients) are set at the mean intake of the reference groups. Actual energy requirements vary depending on activity levels. As opposed to many nonenergy nutrients, excessive caloric intake cannot be excreted and leads to weight gain. Since the DRI (2002), recommendations for energy nutrients are expressed as a range, the Acceptable Macronutrient Distribution Range (AMDR). The AMDR is the range of an energy-yielding macronutrient that is associated with reduced chronic disease while providing adequate levels of essential nutrients.

The Nutrient RDA (A) are set at two standard deviations (SD) above the EAR. The assumption is that this recommendation provides adequate intakes for

97.5% of the population, so that they develop normally and remain healthy. Since for the majority of people, an intake of 77 % of the RDA is adequate, the RDA provide a safety margin. At levels below the RDA, metabolic integrity may be compromised. At levels above the RDA, the likelihood of a deficiency approaches zero.

For most nutrients, there is a large safety margin above the RDA (B). With the exception of selenium, adverse effects appear only at several times the RDA. These amounts are reflected in the Tolerable Upper Intake Levels (UL), above which toxicity becomes apparent. Toxicity symptoms may be mild or more severe (e. g., B6), depending on the nutrient. Even though excessive intake of some energy nutrients causes nutrient-specific degenerative symptoms, no UL were established for energy nutrients, since the relationship between intake and degree of disease is linear, and no threshold could be established.

The difficulty in establishing the RDA lies in the fact that they are by necessity based on estimates derived from representative samples of the population. The RDA represent adequate, but not necessarily optimal intakes. Increasingly, prevention of chronic disease rather than just deficiencies is taken into consideration when setting reference intakes. The representative samples do not necessarily account for individual needs based on age, nutritional status, genetic variability, drug use and abuse, etc. Therefore, the RDA are not a measure to determine where the nutrient supply becomes marginal for the individual. There are presently a host of different nutritional recommendations issued by governmental and other agencies throughout the world (C).

Dri Nutrition

EAR RDA UL NOAEL LOAEL

EAR RDA UL NOAEL LOAEL

When Ear And Rda
UF = Uncertainty factor LOAEL = Lowest Observed Adverse Effect Level

I- C. Nutritional Recommendations

RDA

Recommended Dietary Allowances

US

(1943)

RDA

Recommended Daily Amounts

UK

(1979)

RNI

Recommended Nutrient Intakes

Canada

(1983)

RDI

Recommended Daily Intakes

Australia

(1986)

EAR

Estimated Average Requirement

UK

(1991)

US

(1994)

RNI

Reference Nutrient Intake

UK

(1991)

Food Guide Pyramid

US

(1992)

HEI

USDA Healthy Eating Index

US

(1994)

UL

Tolerable Upper Intake Levels

US

(1994)

DRI

Dietary Reference Intakes

US and Canada

(1997)

AI

Adequate Intake

US

(1997)

AHEI

Harvard School of Public Health

Alternative Healthy Eating Index

US

(2002)

AMDR

Acceptable Macronutrient Distribution Range

US

(2002)

EER

Estimated Energy Requirement

US

(2002)

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Responses

  • AMINA
    What is the nutrient standard when there is insufficient research to determine the rda?
    6 years ago
  • zemzem
    Why the rda added two standard deviations?
    4 years ago

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