Types of SIBO
Hydrogen SIBO is associated with looser stools or irritable bowel syndrome with diarrhea (IBS-d). However, it should be noted IBS-d does not always accompany it.
Methane SIBO is most associated with constipation or irritable bowel syndrome with constipation (IBS-c) but again, not always.
Hydrogen sulphide SIBO
This type of SIBO is usually associated with diarrhea but occasionally also constipation. This type of SIBO is extraordinary. The Hydrogen gas created with this type of SIBO can be converted to hydrogen, methane, or hydrogen sulfide by the bacteria. The hydrogen gas is then converted to methane by archaea which are ancient prokaryotic organisms.
The species Methano-brevibacter smithii is responsible for converting four hydrogen molecules into one molecule of methane in patients who have the methane SIBO. Likewise, five hydrogen molecules can be converted to one hydrogen sulfide molecule if there are sulfate-reducing bacteria present. Methane and hydrogen sulfide are also interchangeable, and that is why sometimes we see constipation in patients who have hydrogen sulfide SIBO.
1 Gaci et al., 2014