Abstract
The effects of dietary supplementation with lactitol on the faecal microflora and intestinal microbial metabolism were studied in experimental pigs and in human volunteers. In pigs fed lactitol, counts of facultative anaerobes, and cnterobacteria in particular, were significantly reduced although the total microflora and obligate anaerobes remained relatively unaltered. In human volunteers, bacterial fermentation of lactitol resulted in caecal acidification as evidenced by marked inhibition of the cholesterol metabolism in the gut and reduced excretion of faecal bile acids and neutral steroids. In pigs, the effect of lactitol on intestinal steroid metabolism was studied throughout the intestine; there was a striking inhibition of both bile acid and cholesterol metabolism in the caecum, proximal and mid-colon. Excretion of urinary volatile phenols was increased in pigs receiving lactitol but no consistent alteration was seen in the human volunteers. We conclude the lactitol is fermented in the caecum and proximal colon of both pig and man and that the resultant lowered pH influences both the composition and metabolic activity of the microflora of the large bowel.