Nath, Wiener, Harper, and Elvehjem (136) demon- 

 strated a marked accumulation of cholesterol in 

 the blood and livers of rats fed 1 percent cholesterol 

 and 10 percent hydrogenated coconut oil, although 

 no accumulation was observed with cholesterol or 

 coconut oil when fed alone. Replacement of 1 

 percent of the coconut oil with an equivalent 

 amount of corn oil resulted in a marked decrease 

 in blood and liver cholesterol and in a proportion- 

 ately greater decrease in total liver lipids. Shapiro 

 and Freedman (170) found that the addition of 

 safflower oil and methionine to a cholesterol- 

 containing and sulfur-deficient diet was more 

 effective in reducing hypercholesterolemia than a 

 supplement of methionine with a hydrogenated 

 fat (Crisco). No exceedingly high levels of 

 cholesterol were observed with the 13 fats in- 

 vestigated by Okey, Lyman, Harris, and others 

 (145) even where cholesterol was included in the 

 diet. The highest value for male rats was 96 

 mg./lOO ml. when coconut oil was fed. Lower 

 values were associated with the more highly un- 

 saturated fats, but there was no consistent trend 

 relating serum levels to the degree of saturation 

 of the dietary fat. 



The influence of the unsaturated fats on serum 

 cholesterol levels does not appear to be related to 

 absorption of the sterol. Lin, Karvinen, and Ivy 

 (117) and Ivy, Lin, and Karvinen (99) reported a 

 limited capacity for cholesterol absorption based 

 on measurements of fecal excretion. Byers and 

 Friedman (37) compared the immediate response 

 of rats to cholesterol added to the diet in soybean 

 oil, corn oil, lard, or coconut oil as determined by 

 measurements in intestinal lymph, and found 

 absorption to be greater with the unsaturated than 

 with the saturated fats. 



Okey and Lyman (143) observed a difference in 

 response to dietary cholesterol depending on the 

 level as well as the kind of dietary fat. Choles- 

 terol levels tended to be higher when cholesterol 

 was fed with 10 percent coconut oil than when fed 

 with an equivalent amount of cottonseed oil. 

 At the 5- and 15-percent levels of these two fats, 

 however, no significant differences were observed. 



Very little has been reported on the serum lipids 

 of rats fed cholesterol-containing foods. Blather- 

 wick, Medlar, Bradshaw, and others (31) reported 

 high plasma cholesterol as well as fatty livers of 

 high cholesterol content as the result of feeding 

 diets containing large amounts of beef liver. 

 Reussner and Thiessen (156) did not determine 

 blood cholesterol values for rats on the cereal and 

 milk or egg and bacon diets, but did obtain evidence 

 of differences in the serum lipid components based 

 on notation rate measurments that showed a 

 much higher value for the S t 12-400 class for the 

 bacon and egg diet than for the cereal and milk 

 diet. Rosenkrantz and Bruger (162) found that 

 the feeding of egg yolk resulted in an elevation of 

 the cholesterol content in blood and liver. 



Although there has been some evidence that 

 dietary cholesterol has little influence on the serum 



cholesterol of human subjects, evidence has 

 increased indicating that under some circum- 

 stances dietary cholesterol may be an important 

 factor in determining serum cholesterol levels. 



A single dose of 10 grams of cholesterol fed in a 

 meal with ample fat caused only a small and 

 transient change in the serum cholesterol of young 

 men (104). Serum cholesterol levels may be 

 elevated, however, as the result of consuming 

 cholesterol-containing foods such as egg (34) or 

 butter (25, 26). From investigations of the re- 

 sponse to various fractions from butter with and 

 without various supplements, Beveridge, Connell, 

 Haust, and Mayer (25) showed that relatively 

 small amounts of cholesterol, depending on the 

 dietary fat with which it is associated, may effect 

 highly significant increases in plasma cholesterol 

 in man. Beveridge, Connell, Mayer, and Haust 

 (27) fed varying levels of cholesterol with a 

 homogenized diet containing 30 percent of the 

 calories as a butter-fat fraction low in cholesterol 

 to a group of university students for a period of 

 16 days. Between intakes of 13 and 634 mg. of 

 cholesterol daily, serum cholesterol levels increased 

 sharply, but no further significant increases were 

 obtained with daily intakes of 1,300 to 4,500 mg. 

 Cook, Edwards, and Riddell (43) reported 15 

 percent absorption of crystalline cholesterol by one 

 subject (male) in contrast to 60 percent when 

 egg was the source of the sterol. A transient 

 elevation in cholesterol was observed, with serum 

 levels returning to normal within 24 hours. For 

 patients with normal fasting serum cholesterol 

 levels, Messenger, Porosowska, and Steele (130) 

 observed an elevation in these levels after feeding 

 egg for a period of 48 days. Okey and Stewart 

 (146) and Okey (141) demonstrated a slight but 

 consistent rise in the cholesterol level of normal 

 women taking four egg yolks daily for 1 month. 



No attempt will be made to review the extensive 

 literature now available on the influence of the 

 degree of saturation of the dietary fat in controlling 

 the level of serum cholesterol in humans. Al- 

 though many factors complicate interpretation of 

 these studies, such as the short duration of the 

 experimental period, the influence of previous 

 dietary history, and heredity, there is considerable 

 evidence that serum cholesterol levels in humans 

 may be reduced by increasing the proportion of 

 unsaturated fat in the diet (109). 



The cholesterol level in rats' blood is generally 

 lower than that observed in humans. This 

 relatively low cholesterol level may be due to a 

 species difference or may be a reflection of the 

 lifelong feeding of diets low in fat and cholesterol. 

 The results reported for BHE rats in this publica- 

 tion indicate that elevated cholesterol levels may 

 occur in rats consuming throughout life diets 

 containing relatively high levels of sucrose and 

 higher levels of fat than are usual for this species. 

 The response of the rat to cholesterol-containing 

 diets does not differ markedly from that of humans 

 to comparable diets. 



