The Surprising Link Between Serotonin & IBS

These are two things that don’t usually appear in the same sentence much:

1. Serotonin
2. IBS

Yet, both are related to the gut (serotonin is mostly made there, and IBS is irritable bowel syndrome that can’t really live anywhere else), and that’s why this topic is…

More than a gut feeling

Researchers (Chiara H. Moretti) have identified two gut bacterial species (Limosilactobacillus mucosae and Ligilactobacillus ruminis) that work together to produce biologically active serotonin.

Importantly, people with IBS were found to have lower levels of Limosilactobacillus mucosae, suggesting the loss of this microbe may reduce serotonin production and disrupt normal bowel movement.

But how?

Serotonin controls gut movement! The gut’s nervous system uses serotonin to coordinate muscle contractions that push food through your intestines, so higher serotonin generally speeds transit while lower serotonin slows it.

In IBS, imbalanced serotonin signaling can make intestinal movement either too fast or too slow, contributing to…

• diarrhea-predominant IBS when serotonin activity is high, or
• constipation-predominant IBS when serotonin activity is low

Further, because the enteric (gut) nervous system communicates with the brain via the vagus nerve, changes in gut serotonin can influence both digestion and symptoms like pain or discomfort (see for example: The Vagus Nerve: The Brain-Gut Highway and The Brain-Gut Highway: A Two-Way Street)

To test this, Dr. Moretti and her team did a mouse study, and found that when the bacteria were introduced into germ-free mice with low serotonin levels and IBS, intestinal serotonin increased, the number of nerve cells in the colon rose, and intestinal transit time returned to normal.

You can read the paper itself, here: Identification of human gut bacteria that produce bioactive serotonin and promote colonic innervation

Want to learn more?

For other less well-known things that serotonin does for us, check out:

Serotonin For More Than Just Happiness

Take care!