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7. Gaps in our knowledge

Given the emphasis placed on possible hitherto unmeasured benefits of supplementation, it is appropriate that these should be investigated. Energy expenditure has been a neglected variable because of the difficulty of measurement and the perhaps unjustified disrepute into which the method has fallen. The doubly-labelled water technique will provide much sought-after information on total daily energy expenditure (TDEE) in free-living conditions, but the traditional techniques of diary recording and indirect calorimetry will be retained to identify the components of TDEE that are changing. Identifying changes of habitual physical activity and, in particular, the pace of work may require new approaches in measurement and recording of the social scientist as well as the physiologist. The effect of changes on interpersonal and social interaction of individuals and families can then be investigated.

Supplementation of an individual clearly affects the family and studies of the effects on the whole family are required. Much remains to be answered about leakage, sharing and substitution. Does sharing within the family reflect family need? Apparently not, as it occurs even when the whole family is supplemented. Sharing does not appear to be related to the extent of the food gap. In children, there is no relation between existing intake and net increase in intake (BEATON and GHASSEMI, 1982) although there was a negative correlation in pregnant Bogota women. Does leakage increase purchasing power and how does this affect the family? Do parents control child supplements or is the child satiated? Is the basic disturbance shortage of food or what is it that limits food intake?

Although the advantages of experimental studies were highlighted earlier, BARRETT (1984) has argued a case for non-experimental designs to compare the effects of several independent variables under conditions in which they normally operate and to allow for covariation. Although this approach may not identify the single most important variable, it is more valid ecologically and may be used to improve the design of subsequent interventions. Pathway analysis may help identify intervening and confounding variables, processes and new outcomes (BEATON, 1982). The smaller and less specific effects of indirect multistage processes make greater demands of large sample sizes, better statistical analysis and variables of higher specificity and sensitivity. There are limits to the number of variables that can be studied, drawn by the cost and the quality of data obtained, and hypotheses have to be refined to identify what needs to be measured. The apparent importance of non-nutritional factors of the social, economic and biological environment in determining the extent of the response to supplementation suggest these as rich areas for study. Measurement of the separate effects of nutrition and health care and education stimulation, and whether a synergism exists, is a priority. Is energy supplementation alone worthwhile? Pleas for functional indices of energy nutritional status continue to be made but this has not been a promising area so far. MARTORELL (1984) recommends an outcome of "social competence" - how good an individual is at everyday tasks - which has considerable merit.

The question and investigation of adaptations to chronic energy deficiency is relevant here. Do the low intakes recorded in many studies represent the habitual intakes of the subjects? Is the de-adaptation of supplementation a real phenomenon? What are the effects of discontinuing supplementation? Can individuals readapt?

The policy issues of whether to target the most needy or most responsive and how these might be identified have not been considered here. However, whether to supplement mothers or infants (LECHTIG and KLEIN, 1980) and whether maternal supplementation can affect the offspring without changing maternal nutritional status are questions that need to be answered. Similarly, the factors responsible for individual variations in responsiveness and even participation have yet to be fully described. In each community, different factors may operate and there may be no circumventing the need for a full description of the ecology of the community.

8. Concluding comments

Energy supplementation alone will not alleviate the widespread problems of chronic energy deficiency which have their roots in poverty and deprivation. The extent of the contribution that supplementation can make has not been evaluated fully because of problems in selecting interventions, targets and outcomes and as yet unmeasured benefits. It is important not to overemphasise these putative effects until they are established.

Supplementation (or refeeding) is more successful in the severe forms of CED that have not been considered here. Given the expense and difficulty in supplementing the diets of milder forms of CED in a whole country or a large part of it some selection of recipients is required. Who these should be, is not to be determined by single variables such as anthropometry, whatever its many advantages. The processes and outcomes of supplementation are more complex and numerous than the direct linear main-effect models portray.


ADAIR, L.S.: Marginal intake and maternal adaptation: the case of rural Taiwan. In: Energy Intake and Activity, E. POLLITT, P. AMANTE (Eds.), pp. 33-55. Alar R. Liss, New York, NY, 1984.

ADAIR, L S., POLLITT E.: Outcome of maternal nutritional supplementation: a comprehensive review of the Bacon Chow Study. Am. J. Clin. Nutr., 41, 948-978 (1985).

AEBI, H., WHITEHEAD, R.G. (Eds.): Maternal Nutrition during Pregnancy and Lactation. Hans Huber, Bern, Switzerland, 1980.

BARRETT, D.E.: Methodological issues in nutritional intervention research. In: Malnutrition and Behaviour: Critical Assessment of Key Issues, J. BROZEK, B. SCHÜRCH (Eds.), pp.585-596. Nestle Foundation Publication Series, Lausanne, Switzerland, 1984.

BARRETT, D.E., RADKE-YARROW, M.: Effects of nutritional supplementation on children's responses to novel, frustrating, and competitive situations. Am. J. Clin. Nutr., 42, 102-120 (1985).

BEATON, G.H.: Evaluation of nutrition interventions: methodologic considerations. Am. J. Clin. Nutr., 35, 1280-1289 (1982).

BEATON, G.H.: Adaptation to and accommodation of long-term low energy intake: a commentary on the Conference of Energy Intake and Activity. In: Energy Intake and Activity, E. POLLITT, P. AMANTE (Eds.), pp. 395-403. Alan R. Liss, New York, NY, 1984.

BEATON, G.H., GHASSEMI, H.: Supplementary feeding programs for young children in developing countries. Am. J. Clin. Nutr., 35, 864-916 (1982).

BERKENFIELD, J., SCHWARTZ, J.B.: Nutrition intervention in the community-the WIC program. N. Engl. J. Med., 302, 579-581 (1980).

BROZEK, J., SCHÜRCH, B. (Eds.): Malnutrition and Behavior: Critical Assessment of Key Issues. Nestlé Foundation Publication Series, Lausanne, Switzerland, 1984.

CHÁVEZ, A., MARTÍNEZ, C.: Growing up in a Developing Community. Instituto Nacional de la Nutricion, Mexico, 1982.

DURNIN, J.V.G.A.: Some problems in assessing the role of physical activity in the maintenance of energy balance. In: Energy Intake and Activity, E. POLLITT, P. AMANTE (Eds.), pp. 101-113. Alan R. Liss, New York, NY, 1984.

ENGLE, P.L., IRWIN, M., KLEIN, R.E., YARBROUGH, C., TOWNSEND, J.W.: Nutrition and mental development in children. In: Human Nutrition. A Comprehensive Treatise, Vol. 1, Nutrition: Pre- and Post-natal Development, M. WINICK (Ed.), pp. 291-306. Plenum, New York, NY, 1979.

HEIMENDINGER, J., LAIRD, N., AUSTIN, J.E., TIMMER, P., GERSHOFF, S.: The effects of the WIC program on the growth of infants. Am. J. Clin. Nutr., 40, 1250-1257 (1984).

JAMES, W.P.T., SHETTY, P.S.: Metabolic adaptations and energy requirements in developing countries. Hum. Nutr.: Clin. Nutr., 36C, 331-336 (1982).

JOOS, S.K., POLLITT, E.: Effects of supplementation on behavioral development in children up to the age of two years: a comparison of four studies. In: Malnutrition and Behavior: Critical Assessment of Key Issues, J. BROZEK, B. SCHÜRCH (Eds.), pp. 507-519. Nestle Foundation Publication Series, Lausanne, Switzerland, 1984.

KENNEDY, E.T., KOTELCHUCK, M.: The effect of WIC supplemental feeding on birth weight: a case-control analysis. Am. J. Clin. Nutr., 40, 579-585 (1984).

KEYS, A., BROZEK, J., HENSCHEL, A. MICKELSEN, O., TAYLOR, H.: The Biology of Human Starvation. University of Minnesota Press, Minnneapolis, MN, 1950.

LAWRENCE, M., LAMB, W.H., LAWRENCE, F., WHITEHEAD, R.G.: Maintenance energy cost of pregnancy in rural Gambian women and influence of dietary status. Lancet, 2, 363-365 (1984).

LAWRENCE, M., SINGH, J., LAWRENCE, F., WHITEHEAD, R.G.: The energy cost of common daily activities in African women: the effect of season and dietary status. Am. J. Clin. Nutr., 42, 753-763 (1985).

LAWRENCE, M., COWARD, W.A., LAWRENCE, F., COLE, T.J., WHITEHEAD, R.G.: Fat gain during pregnancy in rural African women: the effect of season and dietary status. Am. J. Clin. Nutr., 45, 1142-1150 (1987).

LECHTIG, A.: Research design. Am. J. Clin. Nutr., 34, 814-817 (1981).

LECHTIG, A. HABICHT, J-P., DELGADO, H., KLEIN, R.E., YARBROUGH, C., MARTORELL, R.: Effect of food supplementation during pregnancy on birthweight. Pediatrics, 56, 508-520 (1975).

LECHTIG, A., DELGADO, H., MARTORELL, R., YARBROUGH, C., KLEIN, R.E.: Maternofetal nutrition. In: Human Nutrition. A Comprehensive Treatise, Vol. 2, Nutrition and Growth, D.B. JELLIFFE, E.F.P. JELLIFFE (Eds.), pp. 79-127. Plenum, New York, NY, 1979.

LECHTIG, A., KLEIN, R.E.: Maternal food supplementation and infant health: results of a study in rural areas of Guatemala. In: Maternal Nutrition during Pregnancy and Lactation, H. AEBl, R.G. WHITEHEAD (Eds.), pp. 285-313. Hans Huber, Bern, Switzerland, 1980.

MARTORELL, R.: Issues in design and data analyses. In: Malnutrition and Behavior: Critical Assessment of Key Issues, J. BROZEK, B. SCHÜRCH (Eds.), pp. 556-575. Nestle Foundation Publication Series, Lausanne, Switzerland, 1984.

MARTORELL, R., KLEIN, R.E., DELGADO, H.: Improved nutrition and its effects on anthropometric indicators of nutritional status. Nutr. Rep. Int., 21, 219-230 (1980).

METCOFF, J., COSTILOE, P., CROSBY, W.M., DUTTA, S., SANDSTEAD, H.H., MILNE, D., BODWELL, C.E., MAJORS, S.H.: Effect of food supplementation (WIC) during pregnancy on birth weight. Am. J. Clin. Nutr., 41, 933-947 (1985).

MORA, J.O., DE NAVARRO, L., CLEMENT, J., WAGNER, M., DE PAREDES, B., HERRERA, M.G.: The effect of nutritional supplementation on calorie and protein intake of pregnant women. Nutr. Rep. Int., 17, 217-228 (1978).

MORA, J.O., DE PAREDES, B., WAGNER, M., DE NAVARRO, L., SUESCUN, J., CHRISTIANSEN, N., HERRERA, M.G.: Nutritional supplementation and the outcome of pregnancy. 1. Birth weight. Am. J. Clin. Nutr., 32, 455-462 (1979).

MORA, J.O., HERRERA, M.G., SUESCUN, J., DE NAVARRO, L., WAGNER, M.: The effects of nutritional supplementation on physical growth of children at risk of malnutrition. Am. J. Clin. Nutr., 34, 1885-1892 (1981).

MUELLER, W.H., POLLITT, E.: The Bacon Chow Study: effects of nutrition supplementation on sibling-sibling anthropometric correlations. Hum. Biol., 54, 455468 (1982).

NORGAN, N.G., FERRO-LUZZI, A., DURNIN J.V.G.A.: The energy and nutrient intake and energy expenditure of 204 New Guinean adults. Phil. Trans. Roy. Soc. London, B 268, 309-348 (1974).

POLLITT, E.: A critical view of three decades of research on the effects of chronic energy malnutrition on behavioral development. This volume, 1988.

PRENTICE, A.M., WHITEHEAD, R.G., ROBERTS, S.B., PAUL, A.A., WATKINSON, M., PRENTICE, A., WATKINSON, A.A.: Dietary supplementation of Gambian nursing mothers and lactational performance. Lancet, 2, 886-888 (1980).

PRENTICE, A.M., WHITEHEAD, R.G., ROBERTS, S.B., PAUL, A.A.: Long-term energy balance in child-bearing Gambian women. Am. J. Clin. Nutr., 34, 27902799 (1981).

PRENTICE, A.M., WHITEHEAD, R.G., WATKINSON, M., LAMB, W.H., COLE, T.J.: Prenatal dietary supplementation of African women and birth weight. Lancet, 1, 489-492 (1983).

REINA, J.C., SPURR, G.B., BARAC-NIETO, M: Marginal malnutrition in school-aged Columbian children: metabolic rate, estimated daily energy expenditure and dietary intervention. Paper presented at the 1st IDECG Meeting, INCAP, Guatemala, August 3-7, 1987.

RUSH, D., STEIN, A., SUSSER, M.: Diet in Pregnancy: A Randomized Controlled Trial of Nutritional Supplements. Alan R. Liss, New York, NY, 1980.

SCHÜRCH, B., FAVRE, A-M.: Maternal Energy Metabolism in Humans. An annotated bibliography. Nestlé Foundation, Lausanne, Switzerland, 1986.

SINGH, J., COWARD, W.A., PRENTICE, A.M., ASHFORD, J., SAWYER, M., DIAZ, E., WHITEHEAD, R.G.: Doubly-labelled water measurements of energy expenditure in Gambian women during the agricultural season. Proc. Nutr. Soc., 47, 41A (1988).

SPURR, G.B.: Effects of chronic energy deficiency on stature, work capacity and productivity. This volume, 1988.

SUSSER, M.: Prenatal nutrition, birthweight, and psychological development: an overview of experiments, quasi-experiments, and natural experiments in the past decade. Am. J. Clin. Nutr., 34, 784-803 (1981).

WABER, D.P., VUORI-CHRISTIANSEN, L., ORTIZ, N., CLEMENT, J.R., CHRISTIANSEN, N.E., MORA, J.O., REED, R.B., HERRERA, M.G.: Nutritional supplementation, maternal education, and cognitive development of infants at risk of malnutrition. Am. J. Clin. Nutr., 34, 807-813 (1981).

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