Excerpts from Reports of FAO Calorie (1950 & 1957) and FAO/WHO Protein Requirements (1957 & 1965)
"They are in general designed for application to countries or groups within countries. Even for this broad purpose they must be applied in accordance of knowledge of local circumstances. The main responsibility rests here with national nutrition committees and local nutrition experts." (1950, p.2; 1957, p.2).
". . . . Scales of average requirements can never be directly applicable to individuals, and it should be emphasized that the recommendations of the Committee are not intended for this purpose. If they are so used, it becomes the responsibility of nutrition consultants and medical advisers to apply them with due regard to individual variation and idiosynorasy. . . ." (1950, p. 2).
"The figures are for use in evaluating the calories or protein intake of population groups and for planning diets and food supplies."
Requirement at the physiological level.* "the figures relate to food as consumed". . . . "they give the amount of calories needed from food actually consumed. . . .". The method was to assign numerical value to the calorie requirements of a fully defined "reference", and to indicate the adjustments to those values which may be made in order to calculate the requirements of people differing from the reference in age, body size, temperature of environment and activity. 10% is added to obtain a figure for comparison with intake at the retail level (1950, p. 30).
Requirements for health. "Estimates of calorie requirements at the physiological level must represent the needs of fully healthy individuals. They should reflect a food intake which enables people to lead an active life physically, mentally and socially, and to be highly productive in their occupational pursuits" (1957, p. 6).
1. Minimum requirements
Minimum requirements for an individual adult correspond to the smallest amount of protein which will maintain nitrogen balance when the diet is adequate in other respects. For groups of persons the term "minimum requirements" has been taken in the past to mean three different things: (1) the lowest adequate requirement on record for any individual; (2) the minimum requirement for the median or average of the group studied - the "average minimum requirement;" (3) the minimum requirement for the great majority, or all, of the group.
The concept of minimum requirements can also be applied in the period of growth, except that here the criterion becomes the smallest quantity of protein which will support "satisfactory growth." This in turn calls for a definition of satisfactory growth, by no means a simple matter (1957, p.10).
2. Average minimum requirement (a.m.r.) - "the minimum requirement for the median or average of the group studied". For adults it is the a.m.r. for nitrogen equilibrium in healthy adults; for children it is the a.m.r. compatible with a rate of growth characteristic of a representative well fed group of children".
3. Safe practical allowances - The a.m.r. figures are adjusted to allow (a) for for individual variation in requirements and (b) for the quality of the proteins contained in the diet which will not normally correspond to that of the reference protein (1957, p. 12).
With regard to (a) the Committee recommends that, in order to cover the needs of the large proportion of individuals in any population group whose minimum requirements exceed the average minimum requirements, an arbitrary increment of 50 percent over average minimum requirements is advisable. For the period of infancy, an increment of 25 to 30 percent is sufficient.
A second correction factor is needed to relate requirements in terms of the reference protein to the quality of the dietary protein (1957, p. 20).
4. Estimated average protein requirement of a population:
R = (UB + FB + S + C) x 1.1, where
R = requirements of nitrogen per kg body weight per day
UB = basal urinary nitrogen loss per kg body weight per day
FB = basal faecal nitrogen loss per kg body weight per day
S = nitrogen lost from the skin per kg body weight per day (integumental + minimum sweating)
C = nitrogen increment during growth per kg body weight per day
In this formula 1.1 represents an addition of 10% to allow for the stress of ordinary life.
R x 6.25 gives the requirement in terms of reference protein (g per kg body weight per day), 6.25 being the conventional conversion factor (1965, p. 19).
5. Practical Allowence - "20% above the average requirement for reference protein - this covers the requirements of all but a very small proportion of the population.
20% below (the lover level) is that below which protein deficiency may be expected to occur in all but a few individuals (1965,p. 20 & 22).
6. Individual variability - see page 18 of the 1965 report
7. Minimum requirements - see Protein 1 above
8. Average requirement -
This term is used by some authors in a differnt sense from that of average minimum requirements. It is usually employed to imply, somewhat vaguely, the fulfilment of the needs of the "average person" for most of the time, presumably with some margin of safety.
10. Optimum requirements
Optimum requirements are usually understood to represent the amounts of protein which will permit "optimum function", a definition which, though it may have a spurious clarity, is not too helpful. The term implies, no doubt, sufficiency of protein to enable some stores or reserves to be established, but here it should be pointed out that, while some stores of protein are needed to permit resistancs to strees, the desirable size of such stores has not been established and must indeed depend on a variety of circumstances.
11. Recommended allowances
This concept is not very different from that of optimum requirements. In practice, it means little more than a series of recommonded figures or values which, it is felt, will cover the needs of populations with a fairly wide margin of safety. One of the shortcomings of tables of recommended allowances is often the lack of rational explanation of the need for a margin of safety and of the size of the margin suggested. The margin adopted may in fact differ considerably from nutrient to nutrient, for reasons not always obvious to those who have not participated in the establishment of the tables.
With respect both to optimum requirements and recommended allowances, and indeed to the problem of defining requirements in general, it should be borne in mind that setting requirements at levels which are difficult to support on scientific grouds and difficult to attain in practice, tends to discourage constructive action to improve deficient diets.
All the terms discussed above refer simply to "protein" and give no indication of the relation between the type of protein and protein requirements. This, in the Committee's opinion, further decreases their usefulness.
* Underlined phrases are those used in the recommendations of the report.