LIPID METABOLISM.

In light of recent advances in the understanding of the metabolism of fats and other lipids, the viewpoint on the importance of fat as a dietary constituent should be changed. It is no longer to be considered as an optional constituent of the diet but as a required component. On the basis of several types of nutritional evaluation (growth, pregnancy, lactation) generous fat diets have been found to give results superior to those obtained by a low-fat regimen. Fat apparently plays a role in promoting protein storage in the tissues. Recent reports have pointed out that fairly large doses of fat have been introduced by vein into animals over considerable periods of time without any of the harmful effects noted in earlier tests. The use of isotopes, which has helped toward knowledge of the changes which take place in the breakdown of fat in the tissues, may lead to an understanding of the mechanism involved in the formation and destruction of the ketone acids.Cholesterol, which has been considered by many to be a causative agent in one type of cardiovascular disease, probably is manufactured in the body at a greater rate than it can originate from foods. The harmful effects of cholesterol may be related to the speed of synthesis and the rate of destruction as well as to the amount of ready-formed cholesterol taken in foods. One instance in which cholesterol feeds exerts a beneficial effect is in the case of rats suffering from overdosage of thyroid extract.