B-glucuronidase (B-G) is an enzyme that breaks the tight bond between glucuronic acid and toxins in the intestines. The liver and intestine bind toxins, steroid hormones and some dietary components to glucuronic acid. That is a protective process that limits absorption and enterohepatic resorption of toxins, and enhances excretion. A high level of activity of B-G in the gut is not desirable. A low level of B-G activity is not known to be of any direct clinical consequence.

B-glucuronidase is produced by the intestinal epithelium and certain intestinal bacteria. Observational studies have indicated a correlation between high B-G activity and certain cancers, but a definitive causal relationship has not been established. Higher levels of B-G have been associated with higher circulating oestrogens and lower faecal excretion of oestrogens in premenopausal women. A potential dietary carcinogen derived from cooked meat and fish induces high B-G activity and prolongs internal exposure to the toxin in an experimental animal model.