THE NONFERMENTABLE DIETARY FIBER LIGNIN ALTERS PUTATIVE COLON-CANCER RISK-FACTORS BUT DOES NOT PROTECT AGAINST DMH-INDUCED COLON-CANCER IN RATS

The effect of supplementation of the diet with autohydrolyzed lignin o n 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis was studied using 112 male Sprague-Dawley rats. Rats received eight weekly inject ions of DMH (9.5 mg/kg sc) or the saline vehicle solution and then wer e maintained on a basal AIN-76 fiber-free diet or the basal fiber-fi-e e diet plus 5% or 10% (wt/wt) lignin for 24 weeks. Rats were killed 32 weeks after the start of the experiment. Colon tumor incidence, locat ion, and multiplicity were determined. Body weight, caloric intake, fe cal dry weight, gut transit time, pH of cecal contents, and total feca l bile acid excretion were measured. Supplementation of the diet with 5% or 10% lignin resulted in increased fecal dry weight and total feca l bile acid excretion and in decreased gut transit rime, colon pH, and fecal bile acid concentration Dietary lignin did not significantly af fect colon tumor incidence or multiplicity compared with the fiber-fre e diet. Thus dietary supplementation with autohydrolyzed lignin, a foo d fiber with good bulking characteristics, had a significant effect on several factors that have previously been linked to reduction of colo n cancer risk, but the consumption of high levels of lignin did not de crease the risk for colon cancer.