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Recommended Dietary Allowances
(RDAs)
The French expression “Apports Nutritionnels Conseillés” (Recommended Dietary Allowances) was first used in 1981, when the first version of the eponymous guide was published, presenting the results of the work carried out by nutrition specialists gathered for the occasion by Afssa.
The concept of RDA is based on nutritional needs: while Recommended Allowances are a public health issue, i.e. for the population as a whole, nutritional needs are an individual concern, with a medical objective. The latter correspond to an amount of energy or sufficient nutrients to cover net needs (i.e. the quantity of nutrients used after intestinal absorption making up and maintaining reserves), with account taken of the quantity actually absorbed. Here, experiments are the dominant means of defining needs depending on the individual (since the absorption factor varies from one person to the next).
Nutritional needs can be split into two categories of nutrients: those which are vital because the human body cannot synthesise them itself or they cannot be totally replaced by another element; and those called “non-vital”, because the body is able to synthesise them itself. Elements that are “conditionally vital” or “essential” fall outside of these two categories, as they can be synthesised by the body but also need to be obtained from food to reach optimum levels (e.g.: fatty acids). If the study of nutritional needs is conducted on a test group of individuals, the average value obtained is called “average nutritional needs”. It is on a safety basis of 130% (two standard deviations of 15%) of average needs that the recommended dietary allowance for the population is calculated.
The term RDA is deliberately wide, grouping together all vital or non-vital nutrients, and therefore avoids an overabundance of terms covering similar concepts.
RDA: lower and upper limits
Although RDAs define a recommended value, they do not need strict compliance because they correspond above all to an increased average for covering the needs of virtually the whole population (97.5%). They then take account of the constitution of reserves since they are calculated on the basis of net needs. If we stick solely to minimal nutritional needs, with reserves not having been constituted, there follows a risk of deficiency at the slightest nutritional deviation.
In 1996, the Conseil Supérieur d'Hygiène Hublique de France (French High Council for Public Hygiene/CSHPF) defined safety limits for a certain number of vitamins and minerals, calculated using conventional toxicology methods and including a margin allowing the diversity of sensitivity among the population to be taken into account.
It should be noted that these various values are a general indication only, and do not apply during personalised, supervised medical treatment.
RDAs and a changing society
RDA studies cannot make do with values obtained in the past. Data must be updated on a regular basis, in keeping with changes in the society and in scientific knowledge.
In 1992 and 2003, two revisions of the report “Recommended dietary allowances for the French population” were made.
In 2001, RDAs for a certain number of fatty acids were published.
In 2006 discussions on “Updating recommended dietary allowances for fatty acids” were begun.
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