Title: The 1991 COMA Report on Dietary Reference Values (DRVs)
Key words: RDIs, RDAs, validity
Date: Nov 1998
Category: 16. Directory
Author: Dr van Rhijn
The Expert Working Groups, created by the panel on Dietary Reference Values (DRVs), set up in 1987 by the Committee on Medical Aspects of Food Policy (COMA), revised the Recommended Daily Intakes (RDIs) and Recommended Daily Amounts (RDAs) used in the previous COMA reports of 1969 and 1979 respectively. The recommendations on DRVs as defined in the 1991 COMA report are scientifically more sound and comprehensive than those in its predecessor.
Redefined Reference Values
The 1969 & 1979 COMA reports based their recommendations on single figures, defined as RDIs and RDAs respectively, which carried the potential for misuse and misinterpretation. They were set deliberately high (compared to average requirements) to minimise the risk of under nutrition due to the intention to apply them to groups of people rather than to individuals. To avoid potential problems, new values called Dietary Reference Values (DRVs), were set to aid interpretation of dietary information on both groups and individuals, based on assessment of the distribution of requirements for each nutrient. They are estimates of requirements for a population, intended to provide guidance rather than recommendations. , A Gaussian distribution from LRNI (mean – 2SD) – EAR (mean) – RNI (mean + 2SD) is assumed.
The panel found no single criterion to define requirements for all nutrients, so the recommendations are based upon reliable experimental, associations and epidemiological data. For most nutrients, the panel found insufficient data to establish any of these DRVs with great confidence. Thus hypothetical judgements had to be made due to the uncertainties relating to the appropriate parameter by which to assess the requirement and the questionable accuracy of dietary intake data.
Despite this, the panel attempted to set DRVs for energy, protein, fats, sugars, starches, non-polysaccharides (NPS), 13 vitamins, 15 minerals and considered 18 other minerals. They are more elaborate and distinctive than previously, clarifying potential confusion regarding reference values such as ‘total sugar and non-milk sugars’, ‘sodium and salt’, ‘Total fat and saturates’, ‘Fibre and NSP’.
Validity is an expression of the degree to which a measurement is a true measure of what it purports to measure and requires to be compared to a ‘true’ external reference measure. Only ‘relative’ validity can be measured in nutrition, due to the element of bias in measuring dietary intakes. The whole area remains confusing, as the yardsticks are forever changing. As measurement and validation techniques become more accurate over time, however, each subsequent report, such as the DRVs from the 1991 COMA report, will challenge and refine the previous values to become the ‘updated reference’ measures.
Given that validity in nutrition becomes more refined as our measuring tools improve, this latest change in approach and nomenclature has reduced the chance of misunderstanding the true nature of the reference values. They can now be better deployed in a variety of ways in practice, such as yardsticks for surveys (EAR), guidance of dietary composition (RNI), for food labels (EAR) and provide a general guide in assessing the adequacy of an individual’s diet (LRNI/RNI).
These references will be the current yardstick until superceded by more rigorous validity studies.
RDA: The average amount of the nutrient, which should be provided per head of a group of people if the needs of practically all members of the group are to be met. (Average for a group of people).
RDI: The amounts sufficient, or more than sufficient, for the nutritional needs of practically all healthy persons in a population. (Food as actually eaten).
EAR: The estimated average requirement (mean) of a group for a particular nutrient or for energy.
RNI: The amount of a nutrient (mean + 2SD), which is sufficient for almost all individuals. It exceeds the requirement of most people and habitual intakes above RNI are almost certain to be adequate.
LRNI: The amount of a nutrient or energy (mean – 2SD), which is sufficient for only a few individuals. Habitual intakes below the LRNI by an individual will almost certainly be inadequate.
DRV: A general term (statistical concept), which covers all the figures of EAR, RNI, and LRNI. It includes guidance on high intakes, and is presented as average requirements for the population as a whole.
Aggett P. et al. Recommended Dietary Allowances (RDAs), Recommended Dietary Intakes (RDIs), Recommended Nutrient Intakes (RNIs) and population Reference Intakes (PRIs) are not
"Recommended Intakes". Journal of Pediatric Dastroenterology and Nutrition. 1997. 25: 236-241.
Bender A. 1997: Introduction to Nutrition and Metabolism Second Edition. Taylor & Francis Ltd, London.
Department of Health (1991a): Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. Report on Health and Social Subjects No. 41. HSMO, London.
MAFF. 1995: Manual of Nutrition. Tenth Edition. HSMO, London.
Nelson M. The validation of dietary assessment. Chapter 8 pp 241-272. In: Margetts B. & Nelson M. 1998; Design Concepts in Nutritional Epidemiology. Second Edition. Oxford University Press. New York.
Scientific Basis of Nutrition Education: 1996; Health Education Authority. Cromwell Press. Melksham.