FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS	ESN: FAO/WHO/UNU EPR/81/38 August 1981
	WORLD HEALTH ORGANIZATION
	THE UNITED NATIONS UNIVERSITY

Provisional Agenda Item 3.4

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

Rome, 5 to 17 October 1981

EFFECT OF ETHNIC RACIAL AND ENVIRONMENTAL FACTORS

ON

PROTEIN REQUIREMENTS

by

R. Uauy
Institute of Nutrition and Food Technology
INTA
University of Chile

INTRODUCTION:

Man is classified as a vertebrate mammal belonging to the primate order and anthropoid suborder. He/She part of the Hominidae family share the Hominoidea super-family with the great apes wich constitute the Pongidae family. Within the Hominidae family there is only one specie Homo Sapiens. Race can be considered the biological equivalent of sub-specie. Humans have been categorized into four races: caucasoid, negroid, mongoloid and australoids. Modern man is predominantly of mixed racial origin. Although various racial adaptations to specific ecological settings are thought to have occurred migratory forces over recorded history have preserved a common genetic background for mankind (1). Some of these genetic adaptations have nutritional implications and obvious selective value skin pigmentation and cholecalciferol requirement is a good example of this phenomenon. Possible ethnic adaptations in protein metabolism should not be discarded but for practical purposes most countries and nations today represent a blend of two or more races. The future will probably bring further racial integration. Ethnicity is defined more broadly and encompasses not only the racial but also the social and cultural roots of a human group or nation (2).

Our efforts in studying the effects of racial and ethnic influences on protein needs will necessarily be confounded by the fact that the environment will be a major determinant of the phenotypic expression of genotype from the time of conception on. This means that under real life conditions racial, ethnic and environmental factors interact in such a way that their effects remain unseparable. We will analyze in this paper results of protein requirements, a phenotypic trait, obtained by various investigators using comparable methodologies. We will briefly explore how genetics and environment could affect protein needs but will not make efforts of separating them.

Before examining the results of the collaborative research sponsored by UNU, FAO and WHO let us explore what we mean by the term environment. Most people use this term exclusively in the ecological sense to encompass the atmosphere, hydrosphere, lythosphere and the biosphere namely air, water, soil and living organisms which surround us. In adittion to these resources the physical environment includes other components such as climate, energy, gravity, sound, gravitation, altitute, ionic strength which give it specificity. These factors constitute the Habitat. The regulated functional interaction of this dynamic state is called an Ecosystem. The force of man in modifying the environment can not be ignored thus our present definition of environment should also include man's work. The social, economic, cultural and political structures in which humans are organized play major roles in modifying for better or worse the natural environment. The physical infraestructure created by man or technostructures constitute part of an emerging artifical ecosystem. This more comprehensive definition of environment will obviously show the limits of our knowledge on the impact of environmental factors on protein needs. In our studies we are able to control very few of these factors and predictable future changes in the environment will require new insights in this area.

The effects of infection an environment (biosphere) determined phenomenon, on protein requirements have been well documented and are being analyzed in detail in other papers (3). We also have some knowledge on the impact of climatic factors such as environmental temperature and humidity on Nitrogen sweat losses. Information on the effects of altitude, gravity, energy, sound intensity and other components of the Habitat is not available. Wether some of these issues may become relevant for the future remains an open question.

We will review data obtained recently in studies sponsored by UNU, FAO and WHO following comparable protocols pertaining the effects of race, ethnic background and environment on protein requirements.

Effects of ethnic and environmental factors on Obligatory N Losses

Obligatory N losses have been studied in various populations. Measurements done on MIT students served as the basis to estimate requirements used by the FAO/WHO 1971 committe. Since then work in Taiwan, Chile and Thailand has shown that mean obligatory urinary N losses are quite similar for widely different, ethnic groups living in quite varied environments. On the other hand obligatory fecal N losses do show significant differences in these comparative studies (4). Subjects in developing nations excrete close to twice the fixed amount of N lost by MIT students. It is interesting to note that this increased N loss occurs only for the initial collection period (5).

In a study done by our group we observed a highly significant drop in fecal N after the tenth day of the protein free diet. The first collection from day 0 to 10 gave a mean N loss of 16 mg N/kg/day while the second period from day 10 to 18 gave a fixed loss of 8 mg N/kg/day. Skin losses show a significant increase with high environmental temperature. In some cases a compensatory decline in urinary N excretion has been noted.

Table I shows the mean obligatory N loss from several ethnic groups under different environmental conditions.

* all subjects studied were males

Effects of ethnic and environmental factors on the N balance response.

The UNU collaborative research network used the short term N balance response to graded levels of protein intake to estimate requirements. Predicted intakes to meet mean protein needs were obtained by linear regression analysis. These studies were conducted in male subjects of different ethnic groups living under dissimilar environmental conditions using comparable methodology. It is surprising to find that the mean intercepts obtained using diets of comparable protein quality are indeed very much alike (6). If ethnic or racial factors play a role it is not significant enough to modify the mean N Balance response. Environmental factors such as temperature surely act as intervening variables and should be adequately controlled.

Table II compares the N balance response date for various population groups.

* all subjects studied were adult males

The effect of ethnic and environmental factors on fecal N losses is confounded because different population groups consume diets with quite variable composition. The effect of fiber is analysed in detail in a specific background paper. The UNU collaborative study included the evaluation of similar diets in different countries. This allows for a comparison of fecal N losses observed by the different investigators controlling for type of diet. Table III summarizes data of mean fecal N from different studies. The ranges correspond to group means obtained at specific levels of protein intake all of which were within the submaintenance to maintenance range of intakes. It can be observed that fecal N is higher with vegetable protein diets but a higher fecal N is also found in studies from developing nations where environmental sanitation is poorer and subclinical enteropathy is highly prevalent (7). The magnitude of these losses is sufficient to have a significant impact on protein requirements. Protein digestibility in subjects from developing nations is significantly lower. This finding can probably be explained by environmental factors rather than racial. A study from Guatemala and one in Chile has shown that protein digestibility can increase after several months of living in a clean environment. This has been corroborated by improvement of absorptive test and regression of morphological changes at the ultrastructural level.

* all subjects studied were adult males

Taking the heights and weights reported by the various investigators in the UNU coordinated research network significant deviations from the ideal weight for heights are found. Table IV shows the mean weight as % of ideal for various population groups studied.

* data obtained from UNU sponsored studies and compared to WHO standard.

Body composition will probably affect protein and energy needs but this will not be demonstrable unless subjects differ significantly. This question could be explored further pooling data from studies done by the various investigators.

Effects of ethnic and environmental factors on body composition.

The fact that under the experimental conditions used to measure the effects of race, ethnic, ethnicity and environment no significant impact was noted does not fully dismiss the issue. Indeed these factors do affect body composition and hence under some circumstances may modify protein needs. Subjects studied by investigators in developing countries are below ideal weight for height and have a significantly lower proportion of body fat and less skeletal muscle when compared to their USA counterpart of comparable height. The expression of the genotype responsable for stature and somatotype is undoubtedly affected by the environment (8). Subjects chosen as representatives of populations in developing nations are shorter, leaner and have a relatively lower muscle mass as shown by creatinine height ratios. The implications of genetically or environmentally induced differences in body composition on protein requirements should be explored further. Body composition differences explain many age related changes in protein and energy metabolism and requirements. Taking weight as % of ideal weight for a given height as a simple index of body composition we have found for young adult males a highly significant negative correlation between weight as % ideal and energy required to mantain a stable body weight. This is depicted in Fig. 1.

CONCLUSION:

1. Humans constitute a common specie. Racial differences exist but most nations are or will become racially mixed. Our present concept of the environment includes not only the physical world but the Habitat and the socio-cultural components.

2. Ethnic, racial and environmental factors affect protein requirements only if they greatly deviate from the norm. It is impossible to fully separate the genetic and environmental influences on protein needs. Climatic factors such as ambient temperature can modify significantly skin N loss. Fecal N losses are higher in N balance studies conducted in developing countries independent of type of diet and level of intake. Body composition is also affected by genetic environmental interactions but it does not affect protein needs unless subjects differ significantly from the standard.

3. Mean protein requirements derived from the N balance response to graded levels of protein intake are not greatly affected by ethnic or environmental factors. These factors can intervene and determine deviations from the norm. Ambient temperature probably has the most significant effect.

4. Environmental temperature and sanitary conditions as they affect protein digestibility should be considered in establishing protein recommendations for different populations groups. Body composition when it differs significantly from the standard should be included to assess individual requirement.

REFERENCES

1. Capurro, L.: “La crisis ambiental y el Futuro del Hombre”. INTA publication № 09/1981. Santiago-Chile 1981.

2. Webster's New World Dictionary of the American Language. The World Publishing Company, New York 1960.

3. Whitehead, R.G.: Environmental Stressors and Protein Utilization ESN: FAO/WHO/UNU EPR/81/33, August 1981.

4. B. Torun, V.R. Young, and W.R. Rand., eds. Protein-Energy Requirements of developing Countries: Evaluation of New data. United Nations University World Hunger Programme. Food and Nutrition Bulletin. Supplement 5 (UNU) 1981.

5. R. Uauy, E. Yáñez, P. Ballester, G. Barrera, E. Guzman, M.T. Saitua, and I. Zacarías, 1981. Obligatory Urinary and Fecal Nitrogen Losses in Young Chilean Men Fed Two Levels of Dietary Energy Intake. British Journal of Nutrion (In Press)

6. Rand, W.M., Uauy, R., and Scrimshaw N.S. eds. Protein Energy Requirements in Developing Countries: Results of Internationally Coordinated Research. Proceedings of Berkeley Workshop UNU, August 1981.

7. Thomas, G., Clain, D.J., Wicks, A.C.B. Tropical enteropathy in Rhodesia. Gut. 17: 888, 1976.

8. Wolanski, N. Genetic and ecological factors in human growth. Human Biology 42: 349, 1970.