The role of fat in child nutrition.

Abstract

The wide differences in fat content among the milks produced by different mammals seem to indicate that the fat requirements of the newborn are also different. Fat accounts for over 50% of the energy content of human milk. This relatively high fat content can be necessary to meet the baby’s high energy demands during the first weeks of life, when it has a reduced ability to adjust the volume of intake. Data from breast-fed babies showing satisfactory growth indicate that their fat intake up to 5–6 months of age is of the order of 34–45 g/day. Digestion and absorption of fat are influenced by the degree of saturation and molecular size of the fatty acids, and by the triglyceride structure. In general, fats rich in unsaturated fatty acids are better absorbed than saturated fats, both by children and adults. Short-chain fatty acids are better absorbed than those of greater molecular size, for an equal degree of saturation. Fats having most of their palmitic acid esterfied in position 2 are better absorbed than fats having this fatty acid randomly distributed among the three positions of the glyceride. The better absorption of human milk fat as compared to that of cow’s milk can be explained, at least in part, by the preferential esterification of palmitic acid in position 2 of the glycerides of human milk fat. Difficulties with fat absorption are particularly important in premature babies. These babies are able to absorb human milk fat to the extent of 80%, but have a smaller ability to absorb the fat from cow’s milk. Human milk has been shown to contain a lipase which is activated by bile salts and seems to be important for the digestion of milk lipids, particularly the esters of retinol. Current estimates of essential fatty acid (EFA) requirements by infants and children are of the order of 3 % of the total energy intake. This figure is lower than the EFA content of human milk generally reported, but higher than that of cow’s milk. There is no evidence that infants fed solely on cow’s milk during their first 4–5 months have clinical manifestations of EFA deficiency. However, bottle-fed babies tend to have lower EFA levels and higher ratios of trienes to tetraenes in their blood lipids, than breast-fed babies. Plasma cholesterol levels of infants and children are affected by the fatty acid composition of the dietary fat and the plasma cholesterol of brest-fed babies may be reduced by increasing the linoleic acid content of the mother’s milk. This role of fat is of obvious interest in child nutrition, in view of the emphasis currently laid on the early prevention of atherosclerosis. An analysis of this problem is, however, beyond the scope of this discussion.