Breath methane excretion in Hong Kong Chinese children

The factors which determine whether an individual is a methane excretor or a nonexcretor are not clearly understood. Genetic makeup, ethnic origin, diet, environment, or an interaction of all these factors have been implicated. In order to delineate the incidence, the age of onset, and environmental factors that may influence the excretion of methane in our community, we investigated a total of 425 Chinese children in Hong Kong (204 females, 221 males). End-expiratory breath samples were collected after an overnight fast and measured by gas-chromatography using a flame ionization detector. Thirty one children (7.3%) excreted at least 1 ppm methane above the ambient level (median = 6.4, range = 1.8-26.0 ppm). There was no difference in methane excretion status and pattern between the sexes or between children who lived at home and those who lived at an institution. There was a general increase in the number of methane excretors with age, but a statistically significant increase was reached only after 14 years of age. The amount of methane excreted was unrelated to age and there were no excretors detected under the age of 5 years. It is concluded that the methane excretion pattern of these children was generally similar to those previously reported from other regions, but the incidence is much lower and the age of onset appears to be more gradual.