Effect of Dietary Vitamin D₃ (Cholecalciferol) on Colon Carcinogenesis Induced by 1, 2-Dimethylhydrazine in Male Fischer 344 Rats

This study examined the effect of increasing dietary vitamin D on chemically induced colon carcinogenesis. Male Fischer 344 rats were first injected with 1, 2-dimethylhydrazine (200 mg/kg) and then fed one of five dietary levels of vitamin D as cholecalciferol (250, 1,000, 2,000, 4,000, and 10,000 IU/kg diet) for nine months. Dietary vitamin D₃ had no effect on weight gain. Plasma 25-hydroxyvitamin D₃levels were similar for the 1,000 and 2,000 IU/kg groups but varied in a dose-related manner for the other groups. Vitamin D did not significantly alter the tumor incidence in either the distal or the proximal colon. No significant differences in the labeling index were found in either the proximal or the distal colon. Within the distal colon, the proliferative zone increased in a dose-related manner. Distribution of labeled cells within the crypt compartments was not affected by dietary vitamin D. Bone and serum minerals in general were unaffected by dietary vitamin D. This study shows that, at this level of dietary calcium, vitamin D did not affect 1, 2-dimethylhydrazine-induced colon carcinogenesis.