396 RIBOFLAVIN 



any unanimity of opinion. However, if one considers the ratio of riboflavin 

 to food intake, it can be noted that 2 to 3 mg. of riboflavin per kilogram of 

 diet seems to satisfy most of the suggested requirements. Such a figure is 

 only of approximate value, since the protein, fat, and carbohydrate pro- 

 portions of the diet will vary widely. 



1. Effect of Dietary Constituents 



It has been shown^''' -^' ^^ that the fat content of the diet has a marked 

 effect on the riboflavin requirement of the rat. Thus, the replacement of 

 the dextrin in a rat diet with isocaloric amounts of fat increased the amount 

 of riboflavin needed for growth and enabled the production of more severe 

 deficiency symptoms. Riboflavin appeared to play no part in the synthesis 

 of fat, carbohydrate, and protein.^"' ^^ Extra fat gained by rats on high- 

 riboflavin diets may result from the sparing of dietary fat through more 

 efficient utilization of dietary energy.^- Reiser and Pearson^^ found that 

 cottonseed oil in the diet of chicks increased the requirement of riboflavin. 

 Rats fed a diet containing only 2 % of calories as fat required half as much 

 riboflavin as rats fed the standard 20 % fat diet, and rats on the latter diet, 

 in turn, required half as much riboflavin as those fed 40 % of their calories 

 as fat.^ 



It is not possible to vary the amount of fat in a diet without changing 

 the relative concentration of the other constituents. The effects of high-fat, 

 low-fat, high-protein, and low-protein diets on riboflavin requirements of 

 the rat were studied simultaneously by Czaczkes and Guggenheim.^ They 

 noted that rats on low-protein diets needed at least twice as much ribo- 

 flavin as animals kept on a "normal" diet. These authors believe that the 



20 L. C. Norris, H. S. Wilgus, A. T. Ringrose, V. Heiman, and C. F. Heuser, Cornell 

 Univ. Agr. Expt. Sta. Bull. 660, 3 (1936). 



21 R. M. Bethke and P. R. Record, Poultrij Set. 21, 147 (1942). 



22 W. W. Cravens, H. J. Almquist, R. M. Bethke, L. C. Norris, and H. W. Titus, 

 Recommended Nutritional Allowances for Poultry, National Research Council, 

 1946. 



23 T. H. Jukes, E. L. R. Stokstad, and M. Belt, /. Nutrition 33, 1 (1947). 



24 J. C. Fritz, W. Archer, and D. Barker, Poultry Sci. 18, 449 (1939). 



25 D. M. Hegsted and R. L. Perry, /. Nutrition 35, 411 (1948). 



26 B. A. McLaren, E. Keller, D.J. O'Donnell, and C. A. Elvehjem, Arch. Biochem. 

 15, 169 (1947). 



27 A. V. Tunison, D. R. Brockway, J. M. Ma.xwell, A. L. Dorr, and C. M. McCay. 

 N. Y. State Conservation Dept. Cortland Hatchery Rept. No. 11 (1942). 



28 J. H. Shaw and P. H. Phillips, J. Nutrition 22, 345 (1941). 



29 G. J. Mannorling, D. Orsini, and C. A. Elvehjem, /. Nutrition 28, 141 (1944). 



30 E. W. McHenry and G. Gavin, /. Biol. Chem. 125, 653 (1938). 



31 E. W. McHenry and G. Gavin, J. Biol. Chem. 138, 471 (1941). 



32 L. Voris and H. P. Moore, /. Nutrition 25, 7 (1943). 



33 R. Reiser and P. B. Pearson, /. Nutrition 38, 247 (1949). 



