Sugar malabsorption in the bowel can lead to bloating,
cramps,
diarrhea and other symptoms of
irritable bowel syndrome as well as affecting absorption of other nutrients. The
hydrogen breath test is now a well established noninvasive test for assessing malabsorption of
sugars in the small intestine. However, there are patients who can suffer from the same spectrum of malabsorption issues but who produce little or no
hydrogen, instead producing relatively large amounts of methane. These patients will avoid detection with the traditional breath test for malabsorption based on
hydrogen detection. Likewise the
hydrogen breath test is an established method for small intestinal bacterial overgrowth (SIBO) diagnoses. Therefore, a number of false negatives would be expected for patients who solely produce methane. Usually patients produce either
hydrogen or methane, and only rarely there are significant co-producers, as typically the methane is produced at the expense of
hydrogen by microbial conversion of
carbon dioxide. Various studies show that methanogens occur in about a third of all adult humans; therefore, there is significant potential for malabsorbers to remain undiagnosed if a simple
hydrogen breath test is used. As an example, the
hydrogen-based
lactose malabsorption test is considered to result in about 5-15% false negatives mainly due to methane production. Until recently methane measurements were more in the domain of research laboratories, unlike
hydrogen analyses which can now be undertaken at a relatively low cost mainly due to the invention of reliable electrochemical
hydrogen sensors. More recently, simpler lower cost instrumentation has become commercially available which can directly measure both
hydrogen and methane simultaneously on human breath. This makes more widespread clinical testing a realistic possibility. The production of small amounts of
hydrogen and/or methane does not normally produce symptoms, whereas the production of higher levels can lead to a wide range of symptoms ranging from functional disorders of the bowel to low level depression. It is possible that excess methane levels may have more health consequences than excess
hydrogen levels. This review describes the health consequences of methane production in humans and animals including a summary of the state of the art in detection methods. In conclusion, the combined measurement of
hydrogen and methane should offer considerable improvement in the diagnosis of
malabsorption syndromes and SIBO when compared with a single
hydrogen breath test.