USE OF BREATH HYDROGEN AND METHANE AS MARKERS OF COLONIC FERMENTATIONIN EPIDEMIOLOGIC STUDIES - VARIABILITY IN EXCRETION

Breath hydrogen and methane are specific end products of colonic ferme ntation, a process which may play a protective role against colon canc er. To assess the possibility of using these markers in epidemiologica l studies, we characterized the intra- and intersubject variability of breath hydrogen and methane excretion over 15 consecutive days among 32 men and women of various ethnic backgrounds (16 Asians, 8 Caucasian s, 8 Hawaiians). Participants were asked to collect four end-expirator y samples each day, which we had shown previously would optimally char acterize daily hydrogen excretion. There was substantial within-subjec t variation in breath hydrogen over the study, although breath methane levels were more constant over time. We found that about 4 days of me asurement for breath hydrogen and 1 day of measurement for breath meth ane are required to correctly characterize individuals according to th eir long-term excretion of these gases. This was true for Asians and n on-Asians. Although breath methane appears to be more practical to mea sure, it is a less sensitive marker of colonic fermentation than breat h hydrogen. Whereas all subjects excreted hydrogen, only 28% of the su bjects excreted methane, and methane excretor status of a few particip ants varied during the study. Because the breath test is noninvasive a nd reliable, we tested the multiple day collection protocol among colo n cancer patients and controls and found it to be well accepted. We co nclude that it is practical to measure breath hydrogen and methane in large epidemiological studies conducted at the individual level. The p otential use for these markers is discussed.