Influence of diet and age on fecal bacterial enzymes.

The bacterial enzymes beta-glucuronidase, azoreductase, and nitroreductase, all implicated in the etiology of colon cancer, were measured in the fecal microflora of rats and humans. The effect of a high-beef diet and advanced age on the activities of these microbial enzymes were determined in the rat. Rats shifted from a grain to a meat diet showed a 1.5- to 2.5-fold increase in activity of all three fecal enzymes. Animals over 20 months of age, consuming a meat diet, showed a further increase in fecal beta-glucuronidase activity, while the levels of all three microbial enzymes increased in old rats fed a grain diet. Fecal microbial enzyme activities were also measured in humans eating a diet supplemented with bran or wheat germ. Humans receiving fiber supplements consisting of 30 g of bran or wheat germ added to their customary diets did not show significant changes in fecal enzyme activity.