854 XIV. NUTRITIONAL VALUE OF FATS 



some evidence indicates that the longevity of animals on high-fat diets 

 may be somewhat less than that of animals receiving lower levels of fat 

 in the diet. Although Carlson and Hoelzel**" reported that rats fed a 

 mixed diet with a high fat and protein content (see page 851) lived somewhat 

 longer, on the average, than did those receiving a vegetarian diet containing 

 less fat and protein, French and co-workers-'* reached opposite conclusions. 

 They point out that, in the experiments of Carlson and Hoelzel, only one 

 rat lived longer than 1000 days on the mixed diet, while four of the vege- 

 tarian group exceeded this age at the time of death. When diets con- 

 taining 22.7% of fat were fed to rats, they grew as rapidly as did those on 

 carbohydrate diets containing only 3.4% of fat and a lower proportion of 

 calories. However, the life span of the male rats on this relatively high- 

 fat diet decreased markedly from that of the animals on the low-fat diet, 

 and there was also a less pronounced decrease in the longevity of the 

 females. 2^'^^ Thus, the increased efficiency of utilization of the diet, but 

 not the caloric intake 'per se, could be correlated with a decrease in life 

 span. A higher fat content was noted in the livers of the male rats fed 

 the high-fat diet, as contrasted with those on the carbohydrate diet.-^-^* 

 The adverse effects of high-fat diets upon the life span, like those of under- 

 feeding, appear to depend upon the age, strain, and sex of the test animal, 

 and upon the duration of the fat-feeding period. The optimal regimens to 

 ensure longevity lie between the extremes of undernourishment and of 

 high dietary enrichment. Retardation of growth per se does not appear 

 to contribute materially to longevity, and mere acceleration of growth is 

 not directly related to the life span. Evidently growth and longevity are 

 coordinated phenomena governed by the same metabolic principles, but 

 are not mutually interdependent.^- 



In longevity studies conducted in the author's laboratory,^^ in which 

 rats were fed diets containing 3, 9, 18, and 30% cottonseed oil, the best 

 survival was obtained in the two middle ranges. When cellulose was added 

 to the higher fat diets to render them isocaloric with the 3% fat diet, 

 animals receiving the diet containing cellulose and cottonseed oil at the 

 18% level exhibited the lowest mortality rate during the observation 

 period. 



^^ C. E. French, R. H. Ingram, G. P. Barron, J. A. Uram, and R. W. Swift, Federation 

 Proc, 7^, 414(1953). 



62 M. Silberberg and R. Silberberg, Physiol. Revs., 35, 347-362 (1955). 



63 H. J. Deuel, Jr., L. Aftergood, and R. B. Alfin-Slater, Unpublished data, 195G 



