Prevention of precancerous colonic lesions in rats by soy flakes, soy flour, genistein, and calcium

The main purpose of this research was to determine whether diets containing soy products would inhibit the early stages of azoxymethane-induced colon cancer in F344 rats. Additional objectives were to determine whether feedin g starch instead of sucrose, feeding additional calcium (0.5% compared with 0.1%), or feeding a low-fiber powdered enteral formula would influence ear ly colon carcinogenesis. Colon cancer was initiated with 2 injections of az oxymethane (15 mg/kg body wt) and a 12-wk dietary treatment period was star ted 1 wk after the second injection. Precancerous colon lesions were assess ed as foci with aberrant crypts (FAC). The mean numbers of FAC were 133 [so y concentrate (low concentration of phytochemicals)], 111 (starch substitut ed for sucrose), 98 [full-fat soy flakes (whole soybeans)], 87 (defatted so y flour), 77 (0.015% genistein), and 70 (0.5% Ca). The soy flour and full-f at soy flake diets contained 0.049% genistein derivatives (primarily glycos ides), but were less effective in inhibiting the formation of FAC than the diet containing 0.015% genistein (as the aglycone). Eating soybeans and soy flour may reduce the early stages of colon cancer.