880 XIV. NUTRITIONAL VALUE OF FATS 



tract, and the thiamine in the feces may be accounted for by the synthetic 

 action of intestinal microorganisms.^^* Reinhold et al}^'^ found no evi- 

 dence of a thiamine-sparing action by fat. However, another possibihty 

 to account for a thiamine-sparing action of fat is suggested by Whipple 

 and Church, 1^^ who offered experimental evidence to support the hypothesis 

 that animals on fat-free diets receiving thiamine gained more weight than 

 did their mates on the same diet but without the vitamin. They suggest 

 that thiamine functions in the synthesis of fat within the animal body. 

 The decreased excretion of thiamine during a high-carbohydrate intake, 

 observed by Reinhold and co-workers^^* was interpreted as indicating an 

 increased need for the vitamin in the metabolism of the extra carbohydrate, 

 and consequent retention in the tissues. A continuous conversion of 

 carbohydrates into fatty acids is assumed to occur under normal condi- 

 tions. ^^^ If, when fat is fed, the extent of a carbohydrate-fat conversion 

 is reduced, one might expect thiamine to be spared. 



b. Riboflavin and Fat. The nutritional interrelation between fat and 

 riboflavin is even less clear than is that of fat and thiamine. Mannering 

 and his co-workers'^^- ^^^ are of the opinion that more riboflavin is required 

 by rats when they are metabolizing a high-fat diet than when they are 

 receiving a low-fat regimen. One explanation for this augmented require- 

 ment of ribofla\'in when high-fat diets are employed was suggested by 

 Elvehjem;^^'' according to this hypothesis the normal intestinal synthesis 

 of riboflavin is inhibited when fat is substituted for dextrin in the diet, and 

 a greater amount must be recei\'ed from outside sources. According to 

 Czaczkes and Guggenheim,'^" at least twice as much riboflavin must be 

 given for the maintenance of the normal riboflavin level in the organs and 

 in the urine when rats are on high-protein and high-fat diets as is required 

 when they are kept on a "normal" diet. According to Potter et al}"^^ 

 no similar increase in riboflavin requirements on high-fat diets was ob- 

 served in experiments with puppies. Kaunitz and co-workers^^^ noted 



i«* J. G. Reinhold, J. T. L. Nicholson, and K. O'Shea Elsom, /. Nutrition, 28, 51-62 

 (1944). 



D. V. Whipple and C. F. Church, /. Biol. Chem., 114, cvii-cviii (1936). 



R. Schoenheimer and D. Rittenberg, ./. Biol. Chem., 114, 381-396 (1936). 



G. J. Mannering-, M. A. Lipton, and C. A. Rlvehjem, Proc. Soc. Exptl. Biol. Med., 

 46, 100-104(1941). 



88 G. J. Mainiering, 1). Dasini, and C. A. i:ivehjem, ./. Nutrition, 28, 141-156 (1944). 



89 C. A. Klvehjem, ./. .4m. Dietet. Assoc, 22, 959-963 (1946). 



90 J. W. Czaczkes and K. Guggenheim, ./. Biol, ('hem., 162, 267-274 (1946). 

 " R. L. Potter, A. E. Axelrod, and C. A. Elvehjem, ./. Nutrition, 24, 449-460 (1942). 

 92 H. Kaunitz, H. Wiesinger, F. C. Blodi, R. E. Johnson, and C. A. Slanetz, J. Nutri- 

 tion, 52, 467 -4S2 (1954). 



