A DIET CONTAINING CHICKPEAS AND WHEAT OFFERS LESS PROTECTION AGAINST COLON TUMORS THAN A CASEIN AND WHEAT DIET IN DIMETHYLHYDRAZINE-TREATEDRATS

We examined the influence of extruded chickpeas and wheat relative to casein and wheat in a dimethylhydrazine (DMH)-induced colon tumor stud y in male Sprague-Dawley rats. The three diets, based on a modified AI N76 rodent diet with fat present at 10 g/100 g dry matter (DM), were a s follows: casein with wheat starch (Cas/S) as control, casein with wh eat (Cas/W) and chickpeas with wheat (CP/W). All diets were fed from 5 wk of age throughout the 28-wk study. At 28 wk, there was a significa ntly lower incidence of large intestinal tumors in rats fed Cas/W rela tive to those fed CP/W (11 vs. 56%, chi-square test, P = 0.018). The c olonic tumor burden (tumors/tumor-bearing animal) was not different in Cas/W-fed and CP/W-fed rats (1 vs. 1.7), but the tumor mass index was significantly lower in the former group (0.22 vs. 1.21, P = 0.026). R ats fed the CP/W diet had significantly lower plasma cholesterol conce ntration (P < 0.01) than rats fed the other two diets. The cecal conte nts of rats fed the CP/W diet had significantly greater relative weigh ts (46%, P < 0.05) than those of the Cas/W-fed rats; this was associat ed with higher concentrations of all short-chain fatty acids. Fecal an alyses showed significantly (P < 0.05) higher concentrations of total fat (54%), total steroids (83%) and secondary bile acids (179%) in the CP/W-fed rats relative those fed Cas/W. There were higher concentrati ons of nitrogen in the feces of CP/W rats relative to the Cas/W-fed ra ts (84%, P < 0.05), associated with greater fecal weights (67%, P < 0. 05). Although wheat and its fibers have been shown to be protective ag ainst DMH-induced cancers in rats, this was not the case in this study in which chickpeas (45 g/100 g diet) provided the protein and were an important source of soluble fiber. Elevated fat, secondary bile acid concentrations and/or nitrogenous compounds could be responsible for t he increased colon tumorigenesis seen and may reflect a legume effect.