During recent years a marked interest has appeared in the literature in studies on the relation between dietary fat and serum lipids. Investigations have been performed with regard to the amount and, above all, with regard to the composition of the fat supplied. It has been shown that administration of fat containing a large proportion of unsaturated fatty acids lowers the serum lipids (Ahrens et al. 1954, 1957). Most of these studies have been carried out in adult humans, in whom, of course, it is often difficult to limit all extra dietary factors influencing the serum lipids. In newborns, however, it is possible to control such factors, and, in addition, to test a given fat from the beginning of life, thus avoiding the influence a previous diet might have on the results.
It is established that the serum lipids are low at birth, and then subsequently increase (Senn and McNamara,