Submitted to: Cancer Epidemiology Biomarkers and Prevention
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 30, 2001
Publication Date: May 20, 2001
Interpretive Summary: The incidence of certain cancers has been linked to diet. We demonstrated that diets made with a common protein found in milk, whey protein, reduced in the incidence of breast cancer in rats. The current study was conducted to determine if the incidence experimentally-induced colon cancer could be reduced by feeding rats a diet containing whey protein hydrolysate. The data demonstrated a significant reduction in cancer of the colon in whey-fed rats, confirming the epidemiological data. This provides a basis to further study these effects by determining the mechanisms by which whey acts.
Technical Abstract: Epidemiological studies have suggested a relationship between diet and colon cancer incidence. Results from animal studies suggest that whey protein, but not casein protein, may provide protective effects against experimentally induced breast cancer in animals. In the current study, we 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) were maintained on modified AIN-93G diets formulated with a single protein source of either casein or whey. Life-time exposure to these diets was studied in the F1 generation (experiment A) or the F2 generation (experiment B). Male offspring were weaned to the same diets as the dams and were maintained on these diets throughout the study. At the age of 90 days, all rats received azoxymethan once a week for 2 weeks (s.c., 15 mg/kj). Forty weeks after the last azoxymethane injection, all rats were euthanized, the colon was examined visually for tumors, and each tumor was histologically evaluated. The weights 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 with 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 protein-containing diets may reduce the risk of developing colon tumors.