I. Ways of expressing dietary recommendations
The RDA (Recommended Dietary Allowance) covers more than 97% of the population.
Recommended Dietary Allowance (RDA):
The RDA is the
- Recommendation of the Food and Nutrition Board of the United States National Academy of Sciences for nutrient intake levels that it believes will meet the needs of most healthy people in the United States. Health and Welfare Canada publishes an analogous set of recommendations, the Recommended Nutrient Intakes (RNI).
- Mean requirement plus two standard deviations (this would cover 97% of the population) -- this is scientific in the cases where the data are sufficient.
- Plus an increment based on expert opinion -- the result assures that virtually no one will be deficient.
The RDA is based on the population for which the mean and standard deviation were determined. Thus, different populations (children, men, women, etc.) have different RDAs.
For nutrients where the data are insufficient, experts make a guess based on what appear to be typical intakes of healthy-seeming people.
(Note: The RDA for calories is the mean -- for obvious reasons.)