Effect of different dietary fats on oxygen consumption and on serum lipid levels in the baboon (Papio ursinus).

In herbivores such as the rabbit the regulation is easily overloaded; the addition of large amounts of cholesterol to the diet may result in a tenfold increase in the level of cholesterol in the serum. Even in omnivores such as poultry, dietary cholesterol causes a marked rise in serum cholesterol (March, Biely & Lindsay, 1964). Also in man, recent experiments have clearly shown that an excess of dietary cholesterol may raise the level of serum cholesterol (Connor, Stone & Hodges, 1964; Connor, Hodges & Bleiler, 1961 a, b ; Erickson, Coots, Mattson & Kligman, 1963). It can be accepted then that there is a cholesterol-regulating mechanism, easily overloaded in some animals and much more stable in others. For some years it has been known that an excess of dietary fats can also affect the concentration of cholesterol in the blood ; saturated fatty acids raise serum cholesterol level whereas polyunsaturated fatty acids lower it (Kinsell, Michaels, Friskey & Splitter, 1958; Bronte-Stewart, Antonis, Eales & Brock, 1956; Ahrens, Hirsch, Insull, Tsaltas, Blomstrand & Peterson, 1957). Little is known about the mechanism of this effect. We wished to investigate whether excess of saturated or, alternatively, polyunsaturated fat in the diet had some further action on a mammal in addition to the well-known effect on lipid levels. We have therefore studied the effect of such diets on basal oxygen consumption. We have used primates because, like man, they are omnivorous and are thus more likely to respond similarly to changes in diet. Two groups of baboons were studied. One group was given a diet rich in saturated fatty acids and the other group a diet rich in polyunsaturated fatty acids. We have also determined the concentrations of cholesterol and phospholipid in the serums of the animals on the different dietary treatments. 1956).