Colonic hyperproliferation induced in rats and mice by nutritional-stress diets containing four components of a human Western-style diet (series 2).

In a previous study colonic hyperplasia and hyperproliferation were induced in mice and rats by a nutritional-stress diet, based on the AIN-76A semisynthetic diet modified to contain four suggested high-risk components of the human Western-style diet: increased fat and phosphate and decreased calcium and vitamin D contents. In this study the effect of raising calcium alone to near the median level (0.22 mg/kcal) and to a high level (1.3 mg/kcal), comparable to adult human dietary intake, was tested in mice and rats while retaining the three other high-risk components. With median calcium intake the nutritional-stress diet induced hyperproliferation of epithelial cells in colonic crypts, with increased numbers of proliferating cells in crypt columns in sigmoid colon of mice (P less than 0.001) and rats (P = 0.02) and in the ascending colon of mice (P = 0.01). With high calcium intake, hyperproliferation was reduced almost to control amounts in the presence of unchanged fat, phosphate, and vitamin D.