Hydrogen Breath Test
Medical Author:
Jay W. Marks, M.D.
Medical Editor: William C. Shiel,
Jr., MD, FACP, FACR
What is the hydrogen breath test?
The hydrogen breath test is a test that uses the measurement of hydrogen in
the breath to diagnose several conditions that cause
gastrointestinal symptoms. In humans, only
bacteria - specifically,
anaerobic bacteria in the
colon - are capable of producing hydrogen. The bacteria produce hydrogen
when they are exposed to unabsorbed food, particularly sugars and
carbohydrates, not
proteins or
fats. Although limited hydrogen is produced from the small amounts of
unabsorbed food that normally reach the colon, large amounts of hydrogen may be
produced when there is a problem with the digestion or
absorption of food in the
small intestine, that allows more unabsorbed food to reach the colon.
Large amounts of hydrogen also may be produced when the colon bacteria move
back into the small intestine, a condition called
bacterial overgrowth of the
small bowel. In this latter instance, the bacteria are exposed to unabsorbed
food that has not had a chance to completely traverse the small intestine to be
fully digested and absorbed. Some of the hydrogen produced by the bacteria,
whether in the small intestine or the colon, is absorbed into the blood flowing
through the wall of the small intestine and colon. The hydrogen-containing blood
travels to the lungs where the hydrogen
is released and exhaled in the breath where it can be measured.
Next: When is hydrogen breath testing used? »
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