INHIBITION OF METHANOGENESIS BY HUMAN BILE

The factors that regulate methanogenesis in humans have not been estab lished. The presence of bile acid, which is lost into the colon from t he small intestine, may be an important regulatory factor of methanoge nesis. To examine this possibility, the effect of human bile on methan e production by faecal cultures, and the in vivo effect of biliary div ersion on breath methane excretion in a methanogenic choledochostomy p atient, were investigated. Faecal suspensions (0.1%) from five methano genic humans were incubated anaerobically with bile (0.3-30%) from thr ee choledochostomy patients, and headspace methane measured by gas chr omatography. All biles inhibited headspace methane. Inhibition of meth anogenesis was dose dependent, plateaued at 10-30% bile concentration, and was abolished by 0.6% cholestyramine. The maximum inhibition by b ile, median (range), was 38 (0.9-56)% of control methane values. Rever sal of the bile fistula in the fourth choledochostomy patient converte d that subject from methanogenic to 'non-methanogenic' status. It is c oncluded that inhibition of methanogens in the caecum by bile acid cou ld significantly reduce the number of methanogens in the colon. This a nd the effect of transit time could explain much of the known epidemio logy of 'non-methanogenesis', which has been related to obesity, (comp aratively) fast colonic transit in healthy persons, and to small intes tinal Crohn's disease.