Benin: nutritional considerations on trace elements in the diet.

The increasing use of the atomic absorption technique makes it possible to study man's trace-element requirements with a very accurate methodology. Some of these elements are present in the daily diet in minute quantities of micrograms which are, however, indispensable for the proper functioning of the body. But apart from such trace quantities present in conditions which are not affected by abnormal environmental concentration, there may be situations in which trace-element levels in foods and diets reach very high values. If very high, the levels may expose a population to the risk of toxicity; on the other hand, they may lead to wrong interpretations of trace-element requirements because they may lead the nutritionist to regard some high values as normal levels and therefore appropriate for meeting man's requirements. Inversely, they may also induce the nutritionist to regard lower values as unsatisfactory. Therefore, since these environmental factors, which are not always identifiable, can induce erroneous judgements due to overestimation of the requirements, it would seem appropriate, if figures on the total supplies of the diet are to be used, to refer to the tabled values of the individual foods of the diet, rather than to analyses of the whole diet ready for consumption. In fact, an abnormally high or low value of a trace element of any single food of a food composition table would have little influence on the calculation of the total supply of the diet, whereas the use of values obtained from meals which have been exposed to contamination during technological processes(e.g., through the cooking water of foods or cooking utensils) may result in overestimation. However, the analysis of global diets seems to be the method of choice in toxicological research, because in this type of investigations the basic elements of an evaluation often derive indeed from abnormal conditions identified at consumer level. Regarding the importance of copper and iron in haematopoiesis, the following hypotheses can be put forward: (a) In the haematopoietic phenomena occurring in intrauterine life, copper seems to play a role equal to that of iron, and perhaps even more important. (b) This role does not seem to be an autonomous one, but is mediated by availability of serum globulin to the child. In other words, this hypothesis relates the problem more generally to the protein nutrition of mother and foetus...