A reader understands that colonic bacteria ferment sugars and complex carbohydrates in the gut. She wonders what happens to the gas and acids that are produced? Could they build up in the blood stream and cause illness?
The short answer is: No. Unlikely to build up in the blood stream of a person with normal respiratory health or to cause harm. The body has many ways get rid of or use up these normal products of fermentation.
The gases that results from fermentation have several possible fates.
- Some of the bacteria in the colon actually feed on the gases produced in the first round of fermentation. Most of the gases produced are used up that way, provided the right bacteria are present.
- Some of the gas is expelled as flatus (farts).
- Some is absorbed into the blood stream. The gas that is absorbed in the blood stream is carried through the veins to the lungs. It is then exhaled in the breath.
In a person with normal respiratory health, it seems unlikely that gases produced by bacterial fermentation in the gut could build up in the blood or body tissues.
Different colonic bacteria produce different gases during fermentation. Interestingly, studies have shown that IBS patients who exhale methane gas (because they are colonized by methane-producing bacteria) tend to have constipation-predominant IBS. Some people are colonized by bacteria that produce hydrogen sulfide (rotten egg smell). This is pure speculation, but...I have been wondering if one could control bad breath with a FODMAPS elimination diet! Hmmm.
The short chain fatty acids produced during fermentation are actually the preferred energy source for the cells that line the gut, so most are "burned up" right on the spot. Note that these are FATTY acids, not what you typically think of as tissue damaging acids, such as hydrochloric acid. Although chemically defined as acids, fatty acids do not have a low pH, as do even mild acids like acetic acid (vinegar). Fatty acids are the building blocks of food fat and fatty tissue. It seems unlikely that fatty acids produced in the gut would be capable of causing any harmful effects.
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