Small intestinal Bacterial Overgrowth (SIBO): Role of methane & Hydrogen Sulphide Gas

We have discussed in our earlier blog how gut dysbiosis or imbalance in our gut bacteria can make some of the microbes (such as Archaea) move from large intestine to small intestine to feast on the food/nutrients stagnant around small intestine, resulting in small intestinal bacterial overgrowth (SIBO). People suffering from digestive issues exhibit different digestive issues. Whether it is upper gut dysbiosis, colon dysbiosis or SIBO, most people have different symptoms. What is the reason for such diverse symptoms? The research & empirical evidence indicates that different digestive issues & symptoms are attributed to what microorganisms are living in the gut. Six main gases produced in our digestive tract include:

1. Nitrogen-23% to 80%
2. Carbon Dioxide- 5% to 28%
3. Oxygen- 0% to 2.3%
4. Hydrogen-0.01% to 47%
5. Methane-0% to 26%
6. Hydrogen Sulphide

The concentration of these gases may vary depending upon intestinal gas composition.

It is important to note here that our stool is mixture of various gases, undigested fibre, waste product & dead microorganisms. 

Some important aspects of various gases to note here:

1. Carbon Dioxide is produced in our small intestine from gastric acid hydrogen ions communicating with bicarbonate in duodenum.
2. Carbon dioxide is also generated in the jejunum by the degradation of dietary triglycerides to fatty acids. 
3. Bacteria also produce carbon dioxide in the digestive tract through fermentation, but most of the produced carbon dioxide readily enters the bloodstream and it goes out through lungs. 
4. Carbon dioxide is converted into short chain fatty acid(acetate) by specific bacteria producing acetic & into methane by Archaea. This reduces the volume of Carbon Dioxide released very little through bloating. 
5. On the other hand gases such as hydrogen, hydrogen sulphide & methane are released through bloating in large amounts.
6. Nitrogen is the most abundant in the digestive tract since we inhale a lot of it from the atmosphere. Some of it is exhaled while the other enters the bloodstream where it is later diffused into intestinal lumen & released through stool & flatulence. 
7. Nitrogen & carbon dioxide are the only gases on the intestinal act that can be diffused between lumen & bloodstream to bring pressure equilibrium in the digestive tract.
8. Oxygen that we inhale & ingest is utilized by our cells & small amounts are also diffused in intestinal lumen. What is not used is released through stool & flatulence.
9. Different quantities of hydrogen & methane are diffused from intestinal lumen into bloodstream to be exhaled later.

Our intestinal tract & microbiome try to maintain a pressure equilibrium so that bloating rarely occurs. However, when we experience gut dysbiosis or imbalance in our gut bacteria, the composition of different gases in our intestinal tract changes.

Let us discuss how this gases comes into play when we suffer from SIBO.

SIBO can be hydrogen dominant, methane dominant or mix of both. Hydrogen driven SIBO is associated with diarrhea while methane led SIBO is associated with constipation.

SIBO-D (SIBO associated Diarrhea)

In  case of SIBO-D, you are likely suffering from hydrogen producing bacteria dysbiosis. Bacteria produces hydrogen as a result of fermentation of carbohydrates in the gut. As discussed above, hydrogen gas exists naturally in our gut as a byproduct of fermentation. Some of it is absorbed in bloodstream & exhaled & some of it is converted into methane by Archaea & rest is released through stool & expelled. Significant amounts of hydrogen gas are not supposed to exist in the small intestine. Too much of hydrogen gas leads to bloating & abdominal pain & discomfort. Gut dysbiosis produces toxins that causes intestinal discomfort & irritating gastrointestinal lining. These toxins overload TRPV1 interceptors in the gut, thereby drawing more water into the bowel & causing  diarrhea. Diarrhea is considered to be a defense mechanism by our body against gut dysbiosis & toxin release. Some of the hydrogen dominant bacteria also produce serotonin & its production in large amounts can increase the motility. This hydrogen dominant bacterial dysbiosis is responsible for diarrhea.

Hydrogen sulphide dominant dysbiosis: Sulphur is the most abundant mineral since it is used by various living cells in our body Our skin, hair, nails, muscles & bones contain sulphur. Our intestinal mucosal barrier is composed of sulfomucins, and it is essential for the endogenous production of glutathione and insulin. Most of our ingested sulfur which our body uses comes from our digestive system and microbiome breaking down protein into amino acids. Most of the sulphur in our body is used up by our cells & microbiome. Some sulphur metabolism byproducts are excreted from our body. Small amounts of sulphur are converted into hydrogen sulphide. 

Hydrogen sulphide is important since it is used to generate mitochondrial energy & its small amounts are useful in strengthening intestinal mucosal barrier & inflammation. People having healthy gut microbiomes, small amounts of hydrogen sulphide are produced from sulphur containing foods ingested by us. Hydrogen Sulphide dysbiosis normally occurs in upper gut but can also occur in the small intestine & colon. Many bacteria that produces hydrogen sulphide from sulphur colonise upper gut & other parts of our digestive tracts.

What are symptoms of hydrogen sulphide dysbiosis:

1. Rotten egg smelling flatulence & defection. It may become more prominent due to high consumption of sulphur containing foods such as Broccoli
2. Chronic Fatigue syndrome since high amount of hydrogen sulphide is toxic for mitochondria & can lead to oxidative stress
3. Brain fog
4. Low Blood Pressure
5. Constipation
6. Diarrhea
7. Leaky Gut: Too much hydrogen sulphide reduces oxidation of butyrate & increase inflammation
8. Colon Cancer
9. Irritable bowel disease

Which microorganisms in our gut can produce hydrogen Sulphide

1. Akkermansia
2. Bacillus
3. Bilophila
4. Citrobacter
5. Desulfovibrio
6. Desulfobacter
7. Desulfobulbus
8. Campylobacter jejuni
9. Clostridium
10. Enterobacter
11. Escherichia coli
12. Helicobacter pylori
13. Klebsiella
14. Odoribacter
15. Salmonella typhimurium
16. Staphylococcus aureus
17. Prevotella
18. Proteus mirabilis

Methane dominant SIBO-C

Our gut microorganism consists of Archaea. These Archaea in our digestive system feeds off hydrogen that bacteria produce during fermentation of carbs in our gut & as a byproduct of digestion. More fermentation & gases occur in our intestine, more methane archaea produces. Decreased migrating motor complex (MMC) function and lactose malabsorption have been associated with archaeal dysbiosis. Decreased MMC function leads to constipation. Decreased MMC function also leads to an increase of hydrogen that feeds archaea and methane concentrations in the gut, which causes excessive bloating. Unlike bacteria, low serotonin production is associated with low MMC function which explains constipation in methane led SIBO. It is difficult to resolve archaea dysbiosis since archaea are anti-bacterial resistant. The best way to overcome this situation is to reduce the amount of oxygen which has to be fermented. Therefore sometimes it is recommended to reduce the carb intake if your are suffering from SIBO-C. Since Archaea can survive for a long time without hydrogen, a low carb or low FODMAP diet may not be helpful. Increasing MMC function is one alternate way to get relief from this dreaded disease.

If you suffer from too much bloating, constipation or release rotten egg smelling flatulence, you may be suffering from SIBO( either SIBO-D or SIBO-C). The best way is to figure out who are folks living in your gut that may be increasing the production of hydrogen sulphide. Hop on to a free discovery call here with us to find more.: 

Sources:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2564830/

https://biomedres.us/pdfs/BJSTR.MS.ID.000606.pdf

http://www.ncbi.nlm.nih.gov/pubmed/16041645 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3508456/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3508456/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3910452/