Carcinogen binding to various types of dietary fiber.

The percent of the carcinogen 1,2-dimethylhydrazine (DMH) bound to a variety of fibers, such as wheat bran, corn bran, citrus pulp, citrus pectin, and alfalfa, was examined at pH values ranging from 1 to 12. The percent of DMH bound to wheat bran increased from 4% at PH 1 to 55% at pH 2 to 77% at pH 12. A sharp rise in carcinogen binding to corn bran occurred between pH 5% of the DMH was bound and pH 8 where 51% of the DMH was bound. The percent of DMH bound to dehydrated citrus pulp also increased as the pH increased with 10% binding observed at pH 1 and with 57% binding observed at pH 12. Between pH 2 and pH 7, the percent of DMH bound to pectin decreased from 60 to 11%. As the pH became more basic, the percent of DMH bound to pectin increased to 42% at pH 12. The sharpest rise in the percent of DMH bound to alfalfa meal occurred between pH 10.5 and pH 12.0. Results from this experiment showed that the affinity to various types of dietary fibers for the colon carcinogen DMH was differentially affected by pH. These results suggested that the protective effect of certain types of dietary fiber against chemically induced colon cancer my in part be attributed to enhanced carcinogen binding by dietary fiber in the colon.