The basic importance of the knowledge of nutritional requirements for both international and national food and nutrition programmes led FAO to convene a Committee on Calorie Requirements in 1949 (1). The Committee, however, emphasized that its recommendations for estimating the requirements of different countries and population groups were "highly tentative and open to testing and further research". Its recommendations were reviewed in the light of subsequent application and new information by a Second FAO Committee on Calorie Requirements in 1956 (2). This Committee retained much of the first report, but changes included the reassessment of the requirements of children and the methods of making allowances for the influence of age and climate on requirements. The recommendations of this Committee, like those of its predecessor, were also considered provisional and tentative.
A revision of the report was considered some 8 years ago due to new physiological knowledge obtained on measurements of the energy expenditure of man under a variety of conditions and to the rapidly changing manner of life in many sections of the population. In 1964 an FAO/WHO Consultant examined the 1957 report, in particular the sections related to the effects of activity, body size, aging and climate on calorie requirements. The FAO estimates of requirements for children were compared with the revised USA NRC scales (1963). A review of all these aspects by the Consultant, however, indicated that the 1957 report was still a practical working document and that there was not sufficient basis for a revision of the report in a near future (3).
An FAO Committee in 1955 defined Protein Requirements in the light of existing knowledge. It was recognized that the knowledge was incomplete and needed extension at many points through further research. The report (4) was a pioneer attempt to establish protein requirements in terms of a "reference protein" of high nutritive value, taking into account available knowledge of amino acid requirements and the amino acid content of foods. This report stimulated much research and was revised in 1963 by a Joint FAO/WHO Expert Group, giving particular attention to the requirements of adults. This Expert Group also adopted a factorial approach to protein requirements, which made it possible to calculate the requirements for all age groups from existing experimental data, and introduce an allowance for the effect of the stresses of ordinary living (5).
After the publication of the reports on both calorie and protein requirements, the recommendations have been widely applied in many countries. In FAO, the estimations of the calorie requirements and the practical allowances for the intakes of dietary protein have been used to assess the adequacy of calorie and protein supplies in different countries in different regions and for the whole world. The Indicative World Plan Study (1969) used this assessment along with other information as the basis for planning food and nutrition policies as recommended by the study. The current important use is in the FAO Perspective Study for Agriculture Development and for the review of the World Food and Nutrition Situation, the report of which will be published in 1972. The estimated calorie and protein requirements based on recommendations in the two reports have been used to assess the calorie and protein intakes of population groups, as determined by means of food consumption surveys.
The basic approach and methodology for the calorie requirements have received wide approval of national and international authorities concerned with nutrition and health. The general method of approach used by both committees, has been to set the requirements against a reference man and woman under well defined conditions and then to consider the variations introduced by such factors as climate, body weight, age, pregnancy and lactation. The requirements of children have been considered separately.
While the general approach has been widely acceptable, nevertheless several questions have often arisen. Notwithstanding the fact that the 1957 committee had stressed that their recommendations were only provisional and tentative, that their report was imperfect in many respects, many nutrition workers considered the report to convey an impression of scientific precision.
Economists have been critical (6, 7, 8) especially on the applicability of the activity component of the reference man and woman, since it does not apply to the peasant farmers, who constitute the majority of the population in developing countries. In a review in 1964 (7) it was concluded that the recommendations would be tentative and uncertain for Asian countries. The importance to undertake the urgent research set out in the final chapter of the 1967 report was emphasized. The present FAO/WHO Committee would undoubtedly devote much attention to the activity component and should consider the definition of "activity" for countries at different stages of development.
Even if the formulae suggested to relate body weight with calorie requirements are found to be generally applicable, the lack of data on mean body weights in most countries has been a problem and another possible source of error. Often the question has been raised whether the estimation of calorie allowances would be based on actual or on potential body weights.
The allowances for environmental temperature have also been questioned in the light of recent studies, which found an increase in energy requirements for men living and working in the tropics (9), (10). Moreover, the allowances for pregnancy and lactation also require re-examination in the light of recent findings in England (11), which indicate that the factor of 60* as recommended in the 1957 report is probably too low. This may have to be raised to as high as 90.
In arriving at recommended intakes (or allowances) for energy, greater attention should be given to conditions in developing countries. For example, the effects that sanitary conditions of the environment may have on the prevalence of infectious diseases, can play a role by increasing or decreasing the energy requirements. The nature of the diet such as the inclusion of a high percentage of non-digestible fibres, although not directly affecting calorie requirements, can nevertheless influence the amount of food consumed.
The Protein Reports have not been used as extensively, but have stimulated a considerable amount of research. As early as 1966 the FAO/WHO Joint Expert Committee on Nutrition already discussed new data which would permit future Committees to improve on the precision of the factorial methods.
Questions have been raised on the values given to factors in the factorial approach to estimate requirements. For example, data based on measurements of the excretion of endogenous nitrogen after six to ten days of nitrogen deprivation are considered doubtful. After such a period of deprivation the individual cannot be considered normal. Subjects are often anorexic, depressed, have severe headaches and thus cannot be considered to be at a physiological state.
FAO obtained much experience on the application of the 1965 report during the IWP Study for Agriculture Development (1967-69). Problems arose in regard to the adjustment of the reference protein needs by means of a quality factor that is calculated from the overall diet of each country. In the first place the 1965 FAO/WHO report specifically recommended (p.54) that the NPU of the diet should be used for computing requirements. This NPU should be an operative value and therefore it was necessary to apply a method (12), (13) to calculate NPU (op) by means of the protein score.
Moreover, the 1965 report recommended the use of an A/E1 ratio to calculate the protein score. This was found unsatisfactory for several reasons, such as the following:
Because of the above discrepancies, FAO decided on a scoring system that is based on the the essential amino acids per unit of total nitrogen, the A/T2 ratio, as discussed in the NRC/USA report No. 1100 on Evaluation of Protein Quality (1963)
The direct comparison of data on the per caput intake of protein and calories with requirements, as separate figures, is of limited value because particularly in underdeveloped communities there is a very wide range of variation in the distribution of the median values. What is needed is a procedure which first will indicate a deficiency in the total supply, as well as an assessment of the diet in terms of NDpCal%. This can then be matched against a set of the requirements for dietary quality of the more vulnerable members of the community.
The difference between the NDpCal% of the average diet and that of the vulnerable groups will indicate the urgency which policies should be pursued to improve the needs of these groups by redistribution of the available protein-rich foods along with the development of special processed foods.
By calculating the scales of requirements for NDpCal% using the FAO Calorie Requirement Report (1957) and the FAO/WHO Protein Requirement Report (1965), it was clear that the values obtained for NDpCal% could not be recommended, particularly those needed by children in the age range 1-4 years. The table below shows the results of the combination:
| Age and Sex |
REQUIREMENTS | |||
| Reference g/Kg | Protein Cal/Kg | Calories Cal/Kg | NDpCal% | |
|
0 - 3/12 |
2.3 |
9.2 |
120 | 7.7 |
|
9/12 - 12/12 |
1.2 |
4.8 | 120 | 4.8 |
|
1 - 3 yrs |
1.06 |
4.24 | 97 | 4.4 |
|
4 - 6 " |
0.97 |
3.88 | 94 | 4.1 |
|
7 - 9 " |
0.92 |
3.68 | 78 | 4.7 |
|
10 - 12 " M |
0.86 |
3.43 | 70 | 4.9 |
|
F |
0.86 |
3.43 | 70 | 4.9 |
|
13 - 15 " M |
0.84 |
3.36 | 63 | 5.3 |
|
F |
0.84 |
3.36 | 53 | 6.3 |
|
16 - 19 " M |
0.77 |
3.08 | 57 | 5.4 |
|
F |
0.77 |
3.08 | 45 | 6.9 |
|
Adults M |
0.71 |
2.84 | 49 | 5.8 |
|
F |
0.71 |
2.84 | 42 | 6.7 |
The values obtained for NDpCal% requirement for growth and maintenance are also not in agreement with those reported by Miller and Payne - 4.6% for adults, 5.9% for a child of 8 years, 7.8% for a toddler of 2 years, 8.4% for an adolescent of 14 years and 9.5% for a lactating mother (14, 12). Moreover, the NDpCal% requirements in the above table for children aged 1-3 years is only 4.4, a figure considerably less than that for adults (5.8 - 6.7).
An explanation for this discrepancy lies in the differences in the recommendations for children in the two reports - that for calories having been based on ideal body weight, while for protein the recommendation has been based on actual body weight.
Another discrepancy between the two reports is that the calorie recommendations are based on average requirements at the physiological level, while the "practical allowance" for proteins is the average plus 20% - a level which will cover the requirements of all but a small portion of the population (page 22 Ref.4).
The above examples illustrate the experiences of FAO/WHO in the application of the 1957 Calories Report and the 1965 Protein Report. The need to review the existing recommendations is emphasized and, therefore, also the importance of the present meeting. The meeting which considers calorie and protein needs at the same time should utilize a common philosophy, approach and basis for the estimation of requirements and recommended intakes (allowances).
(1) FAO Committee on Calorie Requirements (1950), FAO Nutritional Studies No. 5
(2) Second FAO Committee on Calorie Requirements (1957), FAO Nutrition Studies No. 15
(3) Passmore, R. An assessment of the Report of the Second Committee on Calorie Requirements, FAO, 1964.
(4) Protein Requirements Report of the FAO Committee (1957), FAO Nutritional Studies No.16
(5) Protein Requirements. Report of a Joint FAO/WHO Expert Group (1965). FAO Nutrition Meetings Report Series No. 37; World Health Organization Technical Report Series No. 301
(6) Poleman, T. Some Suggestions for Quantifying the Malthusian Dilemma. Cornell Agricultural Economics Staff Paper No. 4 (April 1968).
(7) McArthur, M. Some Factors Involved in Estimating Calorie Requirements, with Special Reference to Persons Engaged in Agricultural Labour in Asian Countries, J. Roy. Stat. Soc. Series A (general) 127, part 3, 392-408 (1964).
(8) Oshima, B.H.T. Food Consumption, Nutrition and Economic Development in Asian Countries, Economic Development and Cultural Change 15, 385-397 (1967).
(9) Consolazio, D.F. The Energy Requirements for Men Living under Extreme Environmental Conditions, World Rev. Nutr. Dietet. 4, 53 (1963).
(10) Collins, K.J. and Weisier, J.S. Endocrinological Aspects of Exposure to High Environmental Temperatures. Physiol. Rev. 48, 785 (1968).
(11) Thomson, A.M., F.E. Hytten and W.Z. Billewicz. The Energy Cost of Human Lactation. Brit. J. Nutr. 24, 565-572 (1970).
(12) Miller, D.S. and P.R. Payne. Problems in the Prediction of Protein Values of Diets, Protein Concentration and Protein Value. Brit. J. Nutr. 15, 11 (1961).
(13) Miller, D.S. and P.R. Payne. Problems in the Prediction of Protein Values of Diets: The Use of Food Composition Tables. J. Nutr. 74, 413 (1961).
(14) Platt, B.S. and D.S. Miller. Proc. Nutr. Soc. 18, III (1959).
* for the efficiency of human milk production
1 The relationship between the content of an individual essential amino acid in a food protein and the total essential amino acid content. It may be expressed either as milligrams of the individual amino acid per gram of total essential amino acids, or as grams of nitrogen derived from the individual amino acid per gram of nitrogen from all the essential amino acids.
2 The proportion of the total nitrogen derived from essential amino acids. This may be expressed in various ways, e.g. as mg of essential amino acids per gram of total nitrogen content or per gram of protein.
