We previously found red wheat more effective than white wheat in reducing colon cancer risk in rats when fed during initiation and postinitiation stages. Here we examine the effect of wheat on colon cancer risk in early and late postinitiation stages in carcinogen-treated rats. Four groups were fed a basal diet, 1 group a red wheat diet, and 1 group a white wheat diet. After 6 wk, 1 basal, the red and white groups were killed (early postinitiation stage). Of the remaining basal groups, 1 continued on the basal diet, 1 was switched to red and another to white wheat for 8 more wk (late postinitiation stage). Red and white wheat significantly reduced morphological [aberrant crypt foci (ACF)] and biochemical (β-catenin accumulated crypts) markers in both early and late postinitiation stages. Both wheat diets reduced dysplasia markers (sialomucin-expressing ACF and mucin depleted foci), compared to the basal diet, during the late postinitiation stage, but red wheat more so. Only red wheat significantly reduced the number of metallothionein-positive crypts, a stem cell mutation marker, in both stages. Overall, red wheat flour reduced risk markers more than white wheat flour, and this was more pronounced in the late post-initiation stage.
