FACTORS ALTERING XTTTRITIOXAL VALUE 921 



uiiheated lard was employed. Approximately 37% of the animals de- 

 veloped gastric lesions after twelve months, while only 5.7% of the rats in 

 the control group presented lesions. Three of the thirty-one rats which 

 had i)een gi\en subcutaneous injections of heated lard or of partially hydro- 

 genated \'egetable oil developed sarcoma within twelve to eighteen months. 

 No tumors developed in the 150 control rats of the same age and strain. ''^^ 

 Chalmers^*^" reported that tumors of the forestomach could be induced in 

 mice fed a diet containing heated cottonseed oil. Several reports from 

 Peacock ct al.^^^ and from Beck and co-workers^^- indicate a relationship 

 between the oral administration or subcutaneous injection of heated fats 

 and the presence of cancer. 



Further work is necessary before one can decide with certainty whether 

 or not the heating of fats under controlled conditions will induce these 

 deleterious effects. The findings of Farmer, Crampton, and SiddalP^^ 

 should be mentioned. They reported that reproduction and lactation were 

 impaired in female rats by diets containing 10% of linseed oil heated at 

 275°C. This deleterious effect could not be counteracted by a-tocopherol. 



(4) The Effect of Rancidity upon the Nutritional Value of Fats and Oils 



It has long been recognized that rancidity influences the interpretation 

 and outcome of nutritional experiments. According to Greenberg and 

 Frazer,^*^ there are a number of ways in which rancid fats may have an 

 adverse effect upon growth. Thus they may cause a condition of stress 

 brought about by an irritating effect or by the presence of toxic agents. 

 Secondly, they may interfere with the nutritional properties of fat. Thirdly, 

 when rancid fats are present in the diet they may destroy other nutrients. 

 They may possibly alter the intestinal flora. Finally, the principal respect 

 in which rancidity may affect nutritional experiments is by decreasing the 

 food intake of the test animals. Clausen, Barnes, and Burr,^°^ in 1943, 

 called attention to the fact that growth on diets containing various fats 

 was markedly influenced by rancidity. They indicated that "The inad- 

 vertent destruction of dietary essentials and the possible independent toxic- 

 ity of rancid fat are factors that might confuse the interpretation of many 

 diet experiments." Greenberg and Fraser^^^ reported that the presence of 



^'o J. G. Chalmers, Biochem. J., 52, xxxl (1952). 



3«i P. R. Peacock, Brit. Med. Bull, 4, 364-367 (1946-1947); P. R. Peacock and S. 

 Beck, Brit. J. Exptl. Pathol., 24, 143-146 (1943); Nature, 162, 252-253 (1948). 



^^ S. Beck, Brit. J. Exptl. Pathol, 22, 299-302 (1941); S. Beck, A. H. M. Kirby, and 

 P. R. Peacock, Cancer Research 5, 135-139 (1945). 



'*' F. A. Farmer, E. W. Crampton, and M. Siddall, Science 113, 408-410 (1951). 



^^ S. M. Greenberg and A. C. Frazer, J. Nutrition, 50, 421-440 (1953). 



