M. Smithii Breath Test Linked to Human Fat Accumulation

Posted on March 26, 2013

Scientists have linked the content of a person's breath to how susceptible they are to gaining weight. The study - which analyzed the breath content of 792 people - found that a person with high concentrations of both hydrogen and methane gases is more likely to have a higher body mass index and percentage of body fat. A person exhales larger amounts of hydrogen and methane gases when a microorganism called Methanobrevibacter smithii (M. smithii) colonizes the digestive tract. Previous research has shown that M. smithii is the predominant organism in the human gastrointestinal tract responsible for methane production. M. smithii is found in the digestive system of all humans. Scientists believe it is when the M. smithii population becomes too big that it may cause problems, such as body fat accumulation.

Ruchi Mathur, M.D., lead author of the research paper and director of the Outpatient Diabetes Treatment and Education Center in the Division of Endocrinology at Cedars-Sinai in Los Angeles, said in a statement, "Normally, the collection of microorganisms living in the digestive tract is balanced and benefits humans by helping them convert food into energy. When M. smithii becomes overabundant, however, it may alter the balance in a way that makes the human host more likely to gain weight and accumulate fat."

M. smithii scavenges hydrogen from other microorganisms and uses it to produce methane, which is eventually exhaled. A current theory is that this interaction helps hydrogen-producing microorganisms extract nutrients from food more efficiently, which encourages weight gain and obesity in the human host. The researchers say these microorganisms also may play a role in insulin signaling and regulation.

The study was accepted for publication in The Endocrine Society's Journal of Clinical Endocrinology & Metabolism (JCEM).