FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS	ESN: FAO/WHO/UNU EPR/81/INF.1 September 1981
	WORLD HEALTH ORGANIZATION
	THE UNITED NATIONS UNIVERSITY

INFORMATION PAPER NO.1

Joint FAO/WHO/UNU Expert Consultation on Energy and Protein Requirements

Rome, 5 to 17 October 1981

ENERGY AND PROTEIN REQUIREMENTS:

PAST WORK AND FUTURE PROSPECTS AT THE INTERNATIONAL LEVEL

by

J. Périssé
ESN, Rome

English version of a paper
presented at the International
Colloquim CENECA, Paris,
March 1981

Background

In 1932, the League of Nations, alarmed by the disastrous impact of the Great Depression on living conditions throughout the world, undertook a study on the effects of this crisis on public health, particularly on the nutritional status of people in the countries affected. A meeting of Experts was convened in Rome for the purpose of discussing the issue, the first international attempt to deal with the problem of food standards. The meeting also prepared a scale of family coefficients for international use in order to ensure the comparability of findings from household consumption surveys. It was decided to invite Doctors Burnet and Aykroyd to prepare a report on three basic questions:

1. What are the nutritional requirements of human beings? How can they be assessed? How can it be determined whether they are met?
2. What resources are available to meet such requirements?
3. How can available resources best be used for the purpose?

As a follow-up to this study, the League of Nations appointed a technical committee chaired by Professor Mellamby and made up of eminent professors from Austria, Great Britain, France, Italy, the Scandinavian countries, the U.S.A. and the U.S.S.R.

The Technical Committee met in London in November 1935, then in Geneva in June 1936, and published a report on “The physiological bases of nutrition”, proposing the first international table of calorie and protein requirements by age and sex¹.

N.B.: It may be worth noting here that some of the participants in the meeting were called upon to guide FAO's nutritional work immediately following World War II. Thus, Professer André Mayer, of the Collège de France, was a signatory of the FAO charter in 1945 and the first Chairman of the FAO Council. Sir John Boyd Orr, of the Aberdeen Rowett Institute, was the first Director General of FAO (1945–1948). Dr. Aykroyd, author of the first study, was the first director of the FAO Nutrition Division (1946–1960).

1 Report on the physiological bases of nutrition - Quarterly Bull., Health Organization of the League of Nations - Vol. V, Extract No. 6.

This concern with aiding member governments with their food problems prompted by the Great Depression of the 30's, was, understandably enough, one of the first of FAO during the severe food shortages of the immediate post-war years. In fact, shortly after its creation, FAO undertook to define nutritional requirements acceptable by member countries, as a sound scientific basis for the establishment of programmes aimed at improving food supplies.

Calorie requirements

The First FAO Expert Committee on Calorie Requirements was set up in 1949 in Washington, under the chairmanship of Ancel Keys.¹ The Committee defined two “reference persons” chosen from among the human group which had been more carefully studied with respect to anthropometric measurements, physical capacity, food consumption and energy expenditure, that is healthy young men and women living in the temperate zone under satisfactory nutritional conditions.

The Committee also proposed adjustments for assessing the requirements of various population groups living in different environments, based on the following assumptions:

• the relationship between aging in adults and calorie requirements is a linear one. Requirements vary with weight to the power of 0.73. There is a near-linear relationship between calorie requirements and environmental temperature.

• the Committee recognized that the data were highly tentative and agreed to update them in the light of experience gained from their application and of the results of new research suggested in its report.

The Second FAO Expert Committee, meeting in Rome in 1956², confirmed the practicality of the concept of “reference persons”, increased children's requirements and slightly lowered those for adolescent males (Table 1). It also revised some of the adjustments for climate and lactation.

1 Committee on Calorie Requirements, FAO Nutritional Studies no. 5, 1950, FAO Rome.

2 Second Committee on Calorie Requirements - Nutrition Studies no. 15, 1957, FAO, Rome.

A Third Committee of Experts appointed jointly by FAO and the World Health Organization (WHO) met in Rome in April 1971 for a further review of the question of energy and protein requirements in the light of new data¹, which justified the Second committee's decision to increase the requirement for children and reduce it for adolescents. The requirement for reference adults was lowered and the adjustment to energy requirement for body weight was placed on a fully linear basis. The adjustment for climate was eliminated and the allowance for pregnancy doubled.

In short, from a conceptual point of view, the methodology of the three committees was to propose average requirements for a reference man and a reference woman living under strictly specified conditions. The committees then took into account the variations due to various physical activities, climate, body weight, age, pregnancy and lactation, with a view to adjusting the requirements for various populations living in different environments. The experts did not suggest a recommended allowance in excess the average requirements. The fact is that when people have enough to eat, they generally cover their calorie requirements. An intake regularly above or below physiological requirements will modify the body weight and in such cases both excess and deficiency are harmful. The assessed requirements include the energy expended maintaining the body at rest (basal metabolism) and ensuring normal growth in children. An extra allowance is added according to the level of physical acitivity.

Four activity levels have been proposed for adults: light, moderate, heavy, exceptionally heavy. For children, a moderate activity was assumed. But in order to estimate the number of people at nutritional risk, it was found necessary to set up a minimum requirement. The approach suggested in 1975 by a group of FAO/WHO experts² was to define an energy intake meeting the maintenance and growth requirements in children and the maintenance requirement in adults, while supplying a slight energy surplus for the basic activities. Thus, if the energy intake falls below that minimum, the organism will unlikely be able to adapt itself to such conditions, as the margin for reducing voluntary physical activity will be very narrow. Hence a nutritional risk due to a probable calorie deficiency.

1 Special Joint FAO/WHO Expert Committee on Energy and Protein Requirements - Report no. 52 (FAO Meetings on Nutrition), 1973, FAO, Rome.

2 Recommendation of a Joint FAO/WHO Expert Meeting - In “Alimentation-Nutrition”, 1, 2 - 1975, FAO, Rome.

Protein Requirements

In 1936, the Technical Committee of the League of Nations set up recommended levels of protein intake for adults and children. The proposed daily allowance of 1 g of protein per kg of body weight for adults did have an appealing simplicity, but no scientific evidence was found to support it.

In FAO, the question of protein requirements was taken up for the first time in 1955 by an expert committee under the chairmanship of Professor E.F. Terroine¹.

The first problem facing the committee was that of adequately defining the various concepts covered by the term “requirements” (mean, minimum, recommended allowance). It was decided to determine mean minimum requirements such as to maintain nitrogen balance in adults. For the first time, requirements were expressed in terms of a “reference protein” of high nutritive value (milk. egg) and they were set at 0.35 g/kg body weight for adults. As regards children and adolescents, experimental data were extremely limited and requirements were estimated at 0.7 – 0.8 g/kg (Table 2).

The problem of protein requirements was taken up again in 1963 by a Joint FAO/WHO Expert Committee whose concern was particularly with adult requirements². They adopted a factorial approach taking into account the obligatory N losses and the requirements for growth. As their predecessors, they expressed requirements in terms of a high quality reference protein, but proposed that chemical scores for protein value be based on the ratio of each essential amino acid to total essential amino acids (A/E ratio).

The FAO/WHO Experts Committee reconvened in 1971. Assuming a likely lack of correlation between protein intake and protein requirements, a protein deficit is detrimental, but there is no evidence, that protein intakes well above probable requirements are either harmful or beneficial. The problems for the experts was therefore to identify the intake level at which the risk of a deficit is minimal, which meant proposing intake levels likely to cover the protein requirements of virtually the entire population.

1 FAO Committee on Protein Requirements - Nutrition Studies no. 16, 1958 FAO, Rome.

2 Joint FAO/WHO Expert Committee on Protein Requirements - Nutrition Studies no. 37, 1965, FAO, Rome.

Assessing the requirements was a three-stage process. A first series of findings, obtained by the factorial method, made it possible to measure obligatory N losses (urine, sweat, faeces) in individuals receiving a protein-free diet, and to determine the rate of N retention at which the requirements for growth, pregnancy and lactation would be met. A second series of experiments, based on the N balance method, attempted to estimate the minimum N intake required for N balance in adults and N retention in children necessary for satisfactory growth. It was found that even with proteins of high nutritive value such as those of milk and eggs, maintaining the balance required about 30 percent more nitrogen than had been suggested by the findings of the factorial method study.

This average requirement was subsequently increased to allow for individual variations noted in the course of the various experiments. A coefficient of variation was applied to the average figure in order to obtain a “safe level” covering the protein requirements of almost all individuals. Thus, in 1955, for lack of information on individual coefficients of variation, the safe practical allowance proposed was arbitrarily set at about 50 percent above the average requirement (Table 2).

The safety margin, which had been lowered to 20 percent in 1963, was brought up to 30 percent at the 1971 meeting, as the committee, having agreed on a coefficient of variation of about 15 percent for maintenance and growth-according to available data- assumed that a 30 percent increase in average figures was likely to cover the requirements of nearly all the population.

The gaps in knowledge

These various meetings showed the need for new research to provide a sound physiological basis for assessing energy and protein requirements. The 1971 committee was the first to consider energy and protein requirements simultaneously, in an attempt to gain a better insight of their interrelationships. The meeting stressed that when energy intake are insufficient to maintain body weight, the efficiency of protein utilization is lowered as part of the dietary protein is used to provide energy.

It is now obvious that the critical analysis of experimental findings did not pay due attention to the fact that N retention is increased when energy intake is in excess of requirements. Thus, to avoid the risk of confusing the interpretation of N balances with the effects of energy deficits, most scientists set up generous calorie allowances and frequently accepted weight increases in adults. Under these experimental conditions, N losses may have been minimized, leading to some underestimation of the requirements for maintenance in adults.

Moreover, the last committee recognized the urgent need for more information on nitrogen requirements in children, adolescents and elderly people belonging to geographical and ethnic groups others than those in Europe and North America, on which most studies have been focussing to date. In particular, new research is needed on the digestibility (in terms of energy and nitrogen) of the different diets consumed throughout the world, as well as on the body's capacity for N retention for various proteins at different calorie intake levels.

Such other aspects as the effects of climate, infections, variations in basal metabolism and energy expenditure according to the type of activity deserve further exploration for a more realistic adaptation of requirements to the conditions prevailing in various countries.

On-going Research

In view of the concern of international agencies for developing countries and of the extent of nutritional problems in such countries, it was necessary to promote research on populations whose diets and environments differ in many ways from those in industrialized countries.

A research project prepared and managed by FAO and financed by the Danish Development Agency (DANIDA) was implemented in 1977, with three research groups in Guatemala, Thailand and Jamaica. Other research, partly funded by the University of the United Nations (UNU) is under way in several countries of Latin America and Asia under the guidance of Prof. Scrimshaw.

The first results from this research were discussed in 1980 at FAO in Rome¹ and at MIT in Cambridge, Massachusetts². This initial work yielded data on N balance and N losses through urine and faeces. The findings were obtained from groups of young adult males (Brazil, Chile, China, Colombia, Guatemala, Japan, Mexico and Thailand) and children under two years of age (China, Guatemala, the Philippines and Thailand) fed on local diets.

Other studies deal with energy/protein interaction and protein intake in parasite-ridden adults (Korea). A comparative statistical study will be made of the results, as well as of those of research currently conducted according to a standardized process. Such data, which represent a valuable scientific contribution from workers in developing countries, will undoubtedly be taken into account by the FAO/WHO/UNU Experts Group in October 1981 for the purpose of reviewing energy and protein requirements.

1 Report of the informal gathering of investigators to review the collaborative research programme on protein requirements and energy intake, 16–18 January 1980, FAO, Rome, Italy.

2 UNU/IUNS Workshop on Protein-ENergy Requirements, 19–23 May 1980, MIT Cambridge, Mass. USA (working papers)

TABLE 1: Average Calorie Requirements according to Various Committees

1 Including supplement for physical work
2 Overall requirement for the period

TABLE 2: Protein Requirements - g/kg of body weight

1 Increase in mean requirement to attain safe, practical level