Previous - Next
The standardized uniformity of the methodology is useful in the interpretation of similarities and differences in the results from the five countries. These results have advanced our knowledge substantially and have provided a very extensive platform on which a definitive explanation of the energy requirements in pregnancy can be constructed. The situation prior to these studies was one with a serious dearth of comprehensive longitudinal data due, in great part undoubtedly, to the considerable difficulties of selecting a statistically satisfactory sample of women, of standardizing the methodology, of making all the relevant measurements, and of analysing the data. This has resulted in a situation where opposing viewpoints could be equally tenable. Although the complete answer has not been obtained from this extensive and expensive project, it is to be hoped that no-one in the future should speculate about energy requirements of pregnant women on the basis of studies carried out on small numbers of subjects, or on measurements made only on one or two occasions at infrequent intervals.
The very similar results obtained on the Glasgow and Wageningen women of BMR changes, amounts of maternal fat deposited, levels of energy intakes throughout pregnancy, and other data, suggest quite strongly than the situation for women in the developed countries is, in general, one where only small extra intakes of energy are necessary to satisfy requirements. The extra energy requirement seems to be much less than 100 kcal/d (420 kJ), and a recommendation of this quantity should be more than adequate for their needs. The acceptance of this would involve a fundamental change from accepted medical teaching and would also have perhaps some economic importance. We need to await further investigations of the energy expenditures of pregnant women to obtain a fuller explanation of how such a small extra energy intake is sufficient. Another study on a large population in Glasgow whose baseline prepregnant energy intakes and expenditures will be measured (150-200 women for intakes and 50 for expenditures by doubly-labelled water) and who will then be followed through to the end of pregnancy, will hopefully provide further evidence for a more complete physiological explanation.
Unfortunately, but not unexpectedly, the data from the three developing countries are not so homogeneous. Basic differences are present in relation to variables as important as BMR and energy intakes. It is not possible, at present, to make statements about energy requirements which have general applicability to pregnant women in developing countries. Indeed, it is simplistic to believe that general statements for the developing world are possible, without much qualification and reservation.
The major part of the present data hints at the probability that energy intakes are not increased by very much, but there are contradictions to that in the Thai data. More studies of this problem on much larger groups of women, with adequate prepregnant measurements, are needed in the developing world.
The overall conclusions from the present studies have shown, by actual measurement, that the energy costs of pregnancy are about 70,000 kcal or so (290 MJ), and this ought to imply that pregnant women, on average, need 70,000 extra kcal in their diet.
These studies have equally well proven that this cost is not usually reflected in 70,000 extra kcal (292 MJ) being consumed in the diet.
Adaptations appear to occur in normal pregnancy which result in considerable savings of energy, probably in subtle ways by which physical activity is almost unnoticeably reduced. Whether this reduction has social or/and economic consequences seems (on our evidence) unlikely, although this is still something for speculation. If it has no serious drawbacks, perhaps this may have weighty implications for supplementation programmes.
The Nestlé Foundation project has not thus far obtained such comprehensive information on lactation. The data are limited, and deal mostly with body weight, BMR, and energy intakes, but with numbers of individuals and frequency of measurement which allow only tentative conclusions to be reached. The results will therefore be summarized in very brief form.
In The Gambia, the Philippines, and in Holland, the body weights at three months of lactation are all higher (by 1.5 to 3 kg) than in the prepregnant or early pregnancy stage, which seems to signify the probability of a reasonable nutritional state. In Thailand, both body weight and body fatness seem to have increased significantly.
These findings have interesting implications for energy intakes, which are unlikely to be other than at least adequate. The actual energy intakes appear to have increased by about 200 kcal/d in Holland, 400-500 kcal/d in the Philippines, and up to 700 kcal/d in Thailand. Lactation seems, therefore, to require quite large additions to energy requirements in women in these developing countries, and this is such an important finding in its practical implications that it needs further corroboration.
DURNIN, J.V.G.A.: Measuring the expenditure of energy: details of technique. In: Studies on Expenditure of Energy and Consumption of Food by Miners and Clerks, Fife, Scotland, 1952, by GARRY, PASSMORE, WARNOCK and DURNIN. MRC Spec. Rep. Ser., No. 289, London, GB, 1952.
DURNIN, J.V.G.A., BROOKWAY, J.M.: Determination of the total daily energy expenditure in man by indirect calorimetry: assessment of the accuracy of a modern technique. Br. J. Nutr., 13, 41-53 (1959).
DURNIN, J.V.G.A., WOMERSLEY, J.: Body fat assessed from total body density and its estimation from skinfold thickness: measurements on 481 men and women aged from 16 to 72 years. Br. J. Nutr., 32, 77-97 (1974).
HYTTEN, F.E., LEITCH, I.: The Physiology of Human Pregnancy. Blackwell, Oxford, GB, 1971.