Physicochemical environment of the colon.

Epidemiological evidence suggests that 80-90% of colorectal cancer is caused by dietary and environmental factors and that the prevalence of cancer can be altered in low-risk patients by long-term alterations in dietary fibre ingestion. It has therefore become increasingly important to examine the available data on colonic pH and transit, and on faecal short-chain fatty acids in different groups, in order to establish the relationship between fibre intake, colonic acidification and the predisposition to cancer in different ethnic groups.