Dietary whey protein protects against azoxymethane-induced colon tumors inmale rats

Epidemiological studies have suggested a relationship between diet and colo n cancer incidence. Results from animal studies suggest that whey protein, but not casein protein, may provide protective effects against experimental ly induced breast cancer in animals. In the current study, rye investigated the effects of casein and whey diets on chemically induced colon cancer in male rats. Pregnant female Sprague Dawley rats (days 3-4 of gestation) wer e maintained on modified AIN-93G diets formulated with a single protein sou rce of either casein or whey, Life-time exposure to these diets was studied in the F-1 generation (experiment A) or the F-2 generation (experiment B), Male offspring were weaned to the same diets as the dams and were maintain ed on these diets throughout the study. At age 90 days, all rats received a zoxymethane once a week for 2 weeks (s.c., 15 mg/kg), Forty weeks after the last azoxymethane injection, all rats were euthanized, the colon was exami ned visually for tumors, and each tumor was histologically evaluated. The w eights and distribution of all of the tumors were recorded. In experiment A , rats fed the casein diet had a 56% incidence of colon tumors compared wit h 30% of the rats on whey-based diets (P < 0.05), In experiment B, rats fed the casein diet had 50% incidence of colon tumors compared with 29% in the whey group (P < 0.05), There were no significant effects of diet on tumor multiplicity or mass. These results suggest that consumption of whey protei n containing diets may reduce the risk of developing colon tumors.