How Two Gut Organisms Can Cause Digestive Distress

Balance of bacteria and organisms in your gut matters more than you may think. When the bacteria are out of balance, you may experience many bothersome symptoms, such as

• Bloating
• Cramping
• Gas
• Belching
• Constipation
• Diarrhea

There are two types of organisms in the gut. One group is bacteria, the other is an archaea—a one-celled organism like bacteria that also inhabits the gut. An overgrowth of archaea that produces methane gas causes constipation, while overgrowth of hydrogen sulfide producing bacteria causes diarrhea.

Archaea can also cause gastroparesis, a condition in which the signals to the digestive system decelerate, which slows down the digestive processes.

The Vicious Cycle Inside Your Gut

If you have diarrhea-related Small Intestinal Bowel Overgrowth (SIBO), you have an overgrowth of hydrogen-producing bacteria in your small intestine. Bacteria produce hydrogen gas as a byproduct of carbohydrate fermentation in the gut.

An overgrowth of bacteria also produces toxins that irritate the gastrointestinal lining that causes diarrhea. Most of these toxins overload the TRPV1 receptors in our gut, greatly increasing water concentration and gut movements (peristalsis), which cause diarrhea as a defensive mechanism to protect the body from the toxins and bacteria.

If you experience constipation, you likely have an overgrowth of archaea. Archaea in the digestive system feed off of hydrogen that other bacteria produce during the fermentation of carbohydrates in our gut. Archaea then produce methane as a byproduct of their digestion.

The more fermentation and hydrogen gas that occurs in the intestines, the more methane archaea can produce. Methanobrevibacter smithii seems to be the most dominant of the archaea species in the gut, compromising at least 90 percent of the archaea gut flora.

Increased hydrogen-producing bacteria and poor lactose absorption have been associated with an overgrowth of archaea in the gut, gastroparesis (slowing of digestive activities) and constipation.

Decreased migrating motor complex function (or MMC, the process by which the digestive system eliminates waste) also leads to an increase of hydrogen (feeds archaea) and methane concentrations in the gut, which causes excessive bloating. People suffering from archaea overgrowth also have significantly lower colon pH, which can help protect the bacterial overgrowth from immune elimination.

How does archaea dysbiosis further hinder MMC function to the point of chronic constipation? Serotonin (5-HT3 / 5-HT4) is one of the biggest neurotransmitters in the gut associated with regulating proper gut function. Lower amounts of serotonin in the gut lead to reduced function and chronic constipation in methane-dominant SIBO.
Reduced activation of the serotonin receptors in the ileum greatly slows down both gastric emptying of the stomach, which can cause gastroparesis symptoms, and emptying of the small intestine, which can lead to SIBO.

Stopping the Cycle

Bacteria and archaea in the gut feed off each other, so how do you stop the back and forth of bacterial or archaeal overgrowth?

Taking a full-spectrum probiotic while following the FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) diet is usually the best way to maintain balance of the gut bacteria.