Effects of Ingested Fats and Sterols on Sterol Metabolism of the White Rat

In a study of the effects of the ingestion of plant fats and sterols on the metabolism of the white rat, young litter mates were placed on plant diets consisting of a mixture of soy bean meal, corn oil, agar, starch and the Osborne and Mendel salt mixture. The 2 diets used were so prepared that the protein intake would be practically the same for both groups of rats. The fat content of one diet was 11% as compared with 34% for the other. Both were supplemented with a vitamin B yeast concentrate (Harris), carotene, and viosterol. A record of food intake was kept. The sterol contents of the liver, the remaining tissues, the diets, and the feces were determined gravimetrically by means of the digitonin method. The table shows that most of the rats on the high fat diet in series 1 and 3 had a higher percentage of liver sterols than those on the low fat diet. This is not true for series 2 in which not only poor growth was obtained but also in which the experimental period was increased by 3 weeks. The table also shows that the larger percentage of liver sterols cannot be due to sterol mobilization because of the similarity of the sterol contents of the rest of the tissues of all of the rats. Fats may therefore be the precursors of sterols. Such a view would be at variance with one held by Chanutin and Ludewig 1 who state that while carbohydrates cause a deposition of cholesterol in the white rat, fats inhibit that phenomenon. Further data showed that all of the rats synthesized sterols since the amounts excreted in the feces were always larger than those fed.