['The present study was conducted to determine the effects of age and diet (breast milk, milk formula, weaning diet) on the activities of some bacterial enzymes in fecal samples collected from 3- to 24-month-old infants. These bacterial enzymes may generate toxic, mutagenic, or carcinogenic metabolites from plant glycosides (beta-glucuronidase, beta-glucosidase) or from urea (urease).', 'The subjects were 68 healthy children ages 3 (n = 20), 6 (n = 20), 12 (n = 17), and 24 (n = 11) months. None of the children had been given any antibiotics during 4 weeks before collection of the fecal samples. Health status, bowel habits, and food consumption of the children were determined by interview of one of the parents using a structured questionnaire. A spot fecal sample from each child was collected.', 'The activities of beta-glucuronidase and beta-glucosidase increased from 0.52 and 1.17 nmol/min x mg protein (at 3 months) to 1.41 and 2.38 nmol/min x mg protein (at 2 years), respectively. However, at 2 years of age, the children had not yet reached the levels reported in earlier studies on adult populations. Urease activity increased from 4.18 nmol/min x mg protein (at 3 months) to 19.0 nmol/min x mg protein (at 2 years), reaching by 12 months of age the level observed in adults. Breast feeding as such had no consistent effect on fecal bacterial enzyme activities. beta-Glucuronidase and beta-glucosidase were higher in those 6- and 12-month-old children who consumed more meat, fish, sausages, or eggs.'] Do fecal bacterial enzyme activities in infants increase with age and adoption of adult-type diet?