|FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS||ESN:FAO/WHO/UNU/|
|WORLD HEALTH ORGANIZATION|
|THE UNITED NATIONS UNIVERSITY|
Item 2.3.1. of the Provisional Agenda
Joint FAO/WHO/UNU Expert Consultation on Energy and Protein Requirements
Rome, 5 to 17 October 1981.
PHYSICAL QUALITY OF THE DIET AND THE FULFILLMENT OF ENERGY REQUIREMENTS
Dunn Nutrition Unit, Cambridge UK and Keneba, The Gambia
1.1 The energy intake of vulnerable people in the developing world, particularly pregnant and lactating women plus young children with relatively high needs, tends to be lower than desirable for three main reasons: food availability, inequality of distribution within the family, and the low energy density of traditional foods. This position paper concentrates on the last facet.
1.2 Customary foods in the developing world generally have a lower energy density than those eaten in more affluent countries because of the following: (a) a high water content; (b) a low fat content; and (c) being largely cereal and vegetable based, they have a relatively high content of metabolically unavailable carbohydrate (dietary fibre).
1.3 A typical energy density for the overall diet of poor people in many countries in the developing world is 1 kcal/g. Translated into daily intakes this means that to satisfy the current recommended dietary allowance for energy a one year old infant who is not breastfed is expected to eat 1 kg of food, and a lactating mother who is engaged in heavy agricultural work and has fed her baby for over 6 months, in excess of 3 kg of food each day.
1.4 A number of investigators have demonstrated the improbability of such amounts ever being eaten in practice. Rutishauser and Frood1, working on young pre-school children in Uganda, had no difficulty in achieving intakes of 100 kcal/kg body weight and more, despite episodes of infection, when moderately undernourished children were provided with milk-based diets. A comparable group of children, however, in the same metabolic ward failed to consume more than 70% of this amount when plantain based but otherwise quite nutritious local food was provided. Rate of growth and the replenishment of plasma albumin concentrations were dramatically different between the two groups of children. On milk the mean rate of growth was 77 g/d, but only 24 g/d on the local food; mean rates of regeneration of plasma albumin concentrations was 8 times faster on milk compared with local food, in spite of the fact that both the diets had the same protein content after adjusting for protein quality.
1.5 Energy density and the adequacy of food consumption has also been studied objectively by Woolfe et al2 in Ghanaian children aged 1-3 years, some living in a typical village and others in an orphanage. In both locations a wide range of food energy intakes per meal was encountered and this was closely related to the energy density of the foods. Fig. 1 shows the range of observed food energy densities and food intakes and their interaction in meeting the energy requirements of 424 kJ/kg/d. The studies of both Rutishauser1 and Woolfe2 indicate that 700 g is around the maximum weight of food which a 1 year old child can be expected to eat. This means the minimum acceptable energy density is 1.5 kcal/g (see also 3.1).
1.6 A survey of the food intake of lactating women in different parts of the world quickly reveals that although there are large differences between the developing countries and industrialized ones in the amount of energy consumed, 1600 kcal in contrast to 2300 kcal/d3, the weight of food eaten is remarkably the same - around 1.2–1.6 kg/d4.
2.1 Foods from the developing countries have a high water content either because of the composition of the basic staple, as in the case of plantain, or more usually because a considerable quantity of water is added to food during cooking.
2.2 The most frequently encountered example of the latter are the gruels made from cereals such as millet and rice. These are frequently given to babies as complementary foods and in The Gambia their energy content is an average of no higher than 0.6 kcal/g. The reason is that if the food is made much more concentrated a thick gelatinous mixture results which is too viscous for the child to consume. Brandtzaeg5, working in Mysore, India, in association with the UNU, has investigated the traditional technology of malting cereals and legume grains with the aim of decreasing this viscosity. In village trials, conducted after applied investigations in the laboratory, malting was shown to increase the acceptability of grainy foods as weaning mixtures, leading to an increased consumption.
2.3 It needs to be emphasized that the actual water content of each sample of traditional food can vary greatly according to the exact way it has been prepared, and this leads to considerable problems in the interpretation of food intake measurements which make use of food tables as the source of energy and nutrient content. Fig. 2 relates the energy and water contents of typical millet based foods consumed in The Gambia. The three food types are dried steamed millet, dried millet plus groundnut sauce, and millet gruel. Overall measured energy content is clearly closely related to water content, but what is even more important, within a given food type there is a marked variation in water content and hence energy as well. Hudson et al6 have made a special study of food composition related to water content and have emphasized the importance of measuring the latter variable in studies where an accurate measurement of energy and protein intake is required. They have also introduced7 a rapid reliable and simple method for doing this, using the ‘Speedy’ apparatus originally designed to measure the water content of concrete. Each determination takes 5 minutes and no sample preparation is required. Laboratory tests have indicated an accuracy of ± one per-cent water may be obtained for cooked foods. The equipment is simple, robust and relatively inexpensive.
3.1 Food eaten by poor people in the developing world invariably has a low fat content, mainly because fat and high fat-containing foods are much more expensive than high carbohydrate-containing ones. It is obvious from section 2 that the means of increasing energy density cannot lie solely with lowering the water content, as this results in an impossibly stodgy and impalatable product. It would be to the advantage of most groups of people in the poorer countries of the world if there could be an increase in the fat content of this food up to the target set for the affluent countries of the world, namely 30%. A typical value for the proportion of dietary energy derived from fat in Europe and America is currently 40–45%, but in Africa 2–18%. In the group of young pre-school Ugandan children studied by Rutishauser et al1, only 478 g/d of a milk-based diet was necessary to achieve an intake of 410 kJ/kg body-wt, while it required 717 g/d of the local diet (see also 1.5).
3.2 The practical achievement of the relatively high energy requirements of young children plus pregnant and lactating mothers would be facilitated by the availability and proper use of high oil and fat containing foods. The controlled introduction of frying is an obvious way of food preparation which might be considered, but there are other ways of increasing the fat content. In The Gambia the food energy intake of pregnant and lactating mothers has been raised from an average of 1600 kcal/d to 2300 kcal/d by the introduction, under investigative conditions, of a biscuit supplement prepared in the village by the local baker8. The energy density of this biscuit was 6 kcal/g, and because of this it could be consumed without significantly affecting the intake of traditional food at home. The high density of the biscuit was partly due to its low water content, but also because oil was added during preparation.
4.1 When the daily diet is predominantly or exclusively vegetarian in nature there will inevitably be a relatively high proportion of unavailable carbohydrate (dietary fibre). Although in itself dietary fibre is probably beneficial to health, it does mean that the proportion of the food energy which can be used for metabolic processes is considerably less than the bomb calorimetry value. The analysis of unavailable carbohydrate is the subject of a separate position paper prepared by my colleague, Dr D A T Southgate.
4.2 As well as dealing with the analytical complications associated with water content, care must be exercised in the interpretation of food energy intakes calculated from food tables, as many of these have been based on analytical data which are inadequate with regard to unavailable carbohydrate. There is thus a risk that true energy intake is less than the apparent value obtained from food surveys.
5.1 Some types of leguminous foods, like peas and beans, may provide little nourishment when fed to small children because of the cuticle around each seed. This should be taken into account in studies where energy and nutrient intake are being related to physiological function and health. It is also a subject which needs to be considered in food and nutrition education programmes: the crushing of peas and beans either before or after cooking, although an obvious measure, is frequently neglected.
6.1 In food intake surveys, which depend upon food tables for the calculation of energy and nutrient intake. the water content of cooked foods should be measured if at all possible as variations in this component represent a major source of error and inaccuracy.
6.2 The energy density of traditional foods is a critical factor in the translation of recommended dietary allowances into practical food intakes. It should be recognised that with many foods, cooked in the traditional manner, achievement of the RDA for energy may be impossible because of the bulk of food that needs to be consumed. Traditional cooked foods of adequate energy and nutrient density should be identified and given special emphasis in food and nutrition programmes.
6.3 Consideration also needs to be given to raising the fat content of the food eaten in many developing countries, by the introduction of new food technologies and ways of household cooking. Pregnant and lactating women would be particularly helped by this innovation. Apart from its nutritional properties, fat also tends to make rather bland foods more palatable.
6.4 Many current tables of food composition are insufficiently accurate with regard to the metabolizable energy content of cooked foods and to their unavailable carbohydrate content. This is a further potential source of error in the interpretation of food intake surveys. This needs to be rectified as an internationally controlled analytical exercise.
1. Rutishauser, I. H. E. and Frood, J. D. L. (1973) The effect of a traditional low-fat diet on energy and protein intake, serum albumin concentration and body-weight in Ugandan pre-school children. Br. J. Nutr. 29, 261.
2. Woolfe, J. A., Wheeler, E. F., Van Dyke, W. and Oraca-Tetteh, R. (1971) The value of the Ghanaian Traditional diet in relation to the energy needs of young children. Ecology of Food & Nutrition 6, 175–181.
3. Prentice, A. M. (1980) Dietary intake and weight changes during pregnancy: birthweight and lactation capacity in The Gambia. In: Maternal Nutrition in Pregnancy and Lactation, H. Aebi and R. G. Whitehead (eds.). Hans Huber: Berne.
4. Whitehead, R. G. (1979) Infant feedng practices and the development of malnutrition in rural Gambia. United Nations University Food and Nutrition Bulletin 1 (4), 36–41.
5. Brandtzaeg, B. (1979) Village processing of weaning food. Proceedings of the Third European Nutrition Conf. Vår F&oring;da 31, Suppl. 3, 162.
6. Hudson, G. J., John, P. M. V. and Paul, A. A. (1980) Variations in the composition of Gambian foods: the importance of water in relation to energy and protein content. Ecology of Food & Nutrition 10, 9–17.
7. Hudson, G. J. and John, P. M. V. (1980) Measurement of water in food: a rapid simple method. Nutrition Reports International 22, 869–872.
8. Prentice, A. M., Whitehead, R. G., Roberts, S. B., Paul, A. A., Watkinson, M., Prentice, A. and Watkinson, A. M. (1980) Dietary supplementation of Gambian nursing mothers and lactational performance. Lancet ii, 886–888.
Fig. 1. The range of observed food energy densities and food intakes and their interaction in meeting the energy requirements 424 kJ/kg/d of young children in Ghana.
Fig. 2. The relationship between the gross energy content of 3 different types of Gambian food and their water content.