The Effects of Casein and Methionine on the Retention of Hepatic Riboflavin and on the Development of Liver Tumors in Rats Fed Certain Azo Dyes^* Free

Rats fed diets containing an azo dye—DAB,o'Me.DAB, or m'Me.DAB—usually developed more hepatic tumors when the diet contained 12 per cent of casein than when 24 per cent of casein or 12 per cent of casein plus methionine were fed. The effect of the protein on body-weight and general well-being, however, was much more marked than it was on tumor incidence. Both casein and methionine were effective in improving the hepatic retention of riboflavin by rats fed the azo dyes studied. The effect of 12 percent of casein was greater than that of 0.4 per cent methionine.