Butyrate slows the growth of
cancer cells cultured in vitro. To determine the relevance of the fermentative production of
butyrate in vivo, colonic
butyrate concentrations were manipulated by feeding different dietary fibres and were related to tumour development in the rat
dimethylhydrazine model of large bowel
cancer. It has previously been shown that
guar gum and oat bran, while highly fermentable, are associated with low
butyrate levels in the distal colon, while
wheat bran causes significantly higher concentrations. Diets containing these fibres (nominally 10% w:w) were administered for 3 weeks before, for 10 weeks during, and for 20 weeks after
dimethylhydrazine administration, after which animals were killed and examined for tumours. Significantly fewer tumours were seen in the rats fed
wheat bran compared with those fed guar or oat bran, and the total tumour mass was lowest in rats fed
wheat bran. Rats on a 'no added fibre diet' had an intermediate tumour mass. Regression analysis, performed regardless of dietary group, showed that the concentration in stools of
butyrate but not of
acetate or stool volume, correlated significantly (and negatively) with tumour mass. These findings indicate that fibre which is associated with high
butyrate concentrations in the distal large bowel is protective against large bowel
cancer, while soluble fibres that do not raise distal
butyrate concentrations, are not protective. Thus,
butyrate production in vivo does bear a significant relationship to suppression of tumour formation.