Lactulose

A keto analogue of lactose. Primary bile acids are converted to carcinogenic secondary bile acids by colonic bacteria when the colonic pH is high. Addition of lactulose to the diet of experimental animals showed a significant fall in small intestinal and colonic pH. In humans lactulose reduced dehydroxylation of chenodeoxycholic acid to the potentially toxic secondary bile acid lithocholic by over 90%. It is also a substrate for preferential growth of Bifidobacterium longum, a bacteria which has been shown to afford protection against colon tumorigenesis.