[Low methane concentration in the breath of Japanese]

A survey of breath methane excretion in Japanese is reported in this paper. The prevalence of methane excretion was 15% in 231 Japanese subjects, which was significantly lower than the range 33-60% reported in Canada and the USA. The prevalence of methane excretion was only 3% in males between the ages of 18-29 years old. However, it increased with age, and both males and females within the ages of 50-59 years old reached to almost the same value of 25-27%. When both parents were methane producers, 67% of their children were also methane producers. On the other hand, only 6% of the children were methane producers when both parents were methane non-producers. The prevalence of methane excretion was 55% in Caucasians who have lived in Japan for four years or longer. This is the same level reported in Canada and the USA. The effect of familial component and ethnic origin suggested that breath methane excretion is strongly affected by genetic factors.