910 XIV. NUTRITIONAL VALFE OF FATS 



finding that the saturated fatty acid moietj^ of butterfat possesses specific 

 nutritive properties. Jack and co-workers'''''' suggested that either the 

 oleic acid content or the total unsaturation might be a factor contributing 

 to differences in growth of weanling rats fed glyceride fractions separated 

 from milk fat. Heftmann-'"'^ could find no significant difference in weight 

 gain or efficiency of food conversion between two groups of rats, regardless 

 of whether the fat component of a Sherman B diet was the entire fatty 

 acid fraction of butter or the same fatty acids stripped of their low molecu- 

 lar weight fraction. In contradistinction to earlier evidence, Heftmann^"^ 

 reported that, on partial hydrogenation of the butterfat, the efficiency of 

 food utilization was somewhat decreased in male rats when the vitamin A 

 and vitamin D were low in the diet. In contradistinction to earlier re- 

 ports, ^^^"^"^ Geyer et al.^°^ observed that a specific growth-promoting action 

 was exerted by a liquid portion of butter fractionated from an acetone 

 solution by cold crystallization at — 4°C. to remove the solid glycerides. 

 These workers reported a positive result in only a single case ; on repetition 

 of the test, they failed to confirm their earlier findings. Jack and Hin- 

 shaw,^"® as well as Jack et al.,^^^ reported that the liquid fraction of butterfat 

 had higher nutritive properties, provided care was taken to prevent oxida- 

 tion of the unsatiu'ated fraction. Thus, on the one hand, Schantz and 

 co-workers^°° ascribed the growth-promoting action of butterfat to the 

 saturated portion of the fatty acids, while Geyer et al}^^ from the same 

 laboratory, and Jack and co-workers, ^°^ attributed this effect to the un- 

 saturated fraction. This difference in interpretation leaves open to ques- 

 tion the validity of both experimental results. 



In addition to the experiments of the Wisconsin group, Boer and his 

 associates reported that butterfat produces better growth in young rats 

 than do certain vegetable oils. Thus Boer^"' reported better growth on 

 butterfat than on olive oil. However, the choice of olive oil as a representa- 

 tive vegetable fat is a rather unfortunate one, since this oil readily becomes 

 rancid, probably due to its relatively low tocopherol content. One must 

 question the results of experiments in which olive oil was employed unless 

 special precautions were taken to prevent it from becoming rancid: Clausen 

 et al.^^ called attention to the toxicity caused by the feeding of rancid fat. 



301 E. Heftmann, /. Nutrition, 34, 455-467 (1947). 



SOS R. P. Geyer, B. R. Geyer, P. H. Derse, H. Nath, V. H. Barki, C. A. Elvehjem, and 

 E. B. Hart, /. 'Dairy Set., 30, 299-305 (1947). 



"o^ E. L. Jack and E. B. Hinshaw, /. Nutrition, 34, 715-724 (1947). 



307 J. Boer, Acta Brevia Neerl. Physiol. Pharmacol. Microbiol., 11, 180-182 (1941). 



308 D. F. Clausen, R. H. Barnes, and G. O. Burr, Proc. Soc. Exptl. Biol. Med., 53, 17G-178 

 (1943). 



