|Activity, Energy Expenditure and Energy Requirements of Infants and Children (IDECG, 1989, 412 p.)|
(Discussion leader R.C. WEISELL, rapporteur N.S. SCRIMSHAW)
Users of the FAO/WHO/UNU 1985 report on energy and protein requirements wishing to make an estimate of the energy requirements of a certain population have to make a number of assumptions and choices. Many policy makers among them would prefer to be given a simple number to use or misuse, and get frustrated at having to make assumptions and choices.
Another problem is that policy makers often have to think in terms of food needed for a particular population. Besides estimates of dietary requirements this also involves estimates of food lost and food wasted. Those amounts are generally large, typically somewhere between 10 and 40%, and estimates of this proportion are very imprecise. Slight adjustments of what are believed to be the physiological requirements therefore appear relatively unimportant.
Recommendations of changes in requirements always cause some confusion; they therefore have to be well-founded. Policy makers operate with very rough estimates which are codetermined by political considerations. One nation, for instance, claims to need food imports based on a per capita requirement of 2500 kcal/d, which donor agencies find too high. Nutritionists should be able give advice in such a situation.
Many policy makers have now accepted the general assumption that, under most circumstances, when energy requirements are met, needs of other nutrients are met as well. Several participants at the workshop expressed doubts about the general validity of this assumption and suggested that the situation might be different for well-nourished and malnourished children and when infection is present. If so, these would become factors to be considered when making policy decisions.
Theoretically, food aid and food supplements should be targeted at those who need them most. In practice, food is often distributed indiscriminately in a certain geographic area, because it is too difficult to select those in greatest need and then to ensure that they are the ones who get most or all of it.
Traditionally, nutritional requirements have been discussed and defined by experts at meetings lasting a few days. This may not be the best method of systematically taking into account large amounts of complex research results. More frequent reviews by small working groups who prepare position papers before the official expert consultation takes place, might be useful. For energy requirements, IDECG should play a role in such preparatory work by small groups.
The extent to which other nutrients may have an effect on energy requirements is hard to establish. Energy and iron deficiency are both frequent and often associated, and the symptoms they produce are sufficiently similar to make it difficult to determine which of the two is more limiting in the diet. From a physiological point of view, regulatory mechanisms appear to be related primarily to energy. This seems to pose no major problems as long as energy demands are covered. When this is not the case and regulatory mechanisms are no longer able to function, other nutrients may become deficient by association. Changes in life style can affect energy demand and, with it, the intake of other nutrients.
Policy makers are interested in the relationship between energy and nutrient requirements on the one hand, and the bioavailable energy and nutrient content of diets and food rations on the other. It appears difficult to deal with problems of energy and protein metabolism separately, and the suggestion was made that IDECG should become a Protein-Energy Consultancy Group.
We need to know more about energy and nutrient requirements during catch-up growth after infections. Our knowledge of functional correlates of anthropometric data is still very limited. What are the differences between wasting and stunting? Does stunting have important functional consequences? If so, how can it be prevented?
NCHS growth curves are useful as a reference, but policy makers often believe that all children have to grow along these curves. Under these circumstances, how do we deal with all the new information that breast- and bottle-fed infants differ in growth? Should the references be changed? To do so, we need more information regarding what growth can be considered optimal.
NCHS is working on a revision of their growth-reference data because the old references are no longer representative of the growth of U.S. children. Since NCHS references, however, are used internationally, should not new references be elaborated by an international team of scientists and based on all appropriate data currently available?
Decisions on optimal growth remain speculative as long as they are not related to functional outcomes. At present, we do not even seem to know whether breast- or bottle-feeding produces the better long-term outcome.