Everyone has a separate, mostly independent nervous system in their gut called the enteric nervous system. One hundred million nerve cells distributed throughout your digestive system direct movement through your intestines.
This "second brain" can work independently of the one in your head, but there is an awful lot of talk back and forth between the two. Just think of butterflies in your stomach when you're nervous, or how anxiety can easily trigger your IBS cramps.
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Mind and Stomach
The brain and the gut have a lot in common, including the ways in which nerve cells talk with each other. Neurotransmitters are important chemicals that allow nerve cells to communicate. Serotonin is one of the most important neurotransmitters for that brain in your gut.
Serotonin is important for the functions of your brain and your mood, but it is crucial to the function of your digestive system. Your gut creates 95 percent of the serotonin in your body. Changes in your levels of serotonin and your sensitivity to serotonin signaling can change how your bowel works.
A popular group of antidepressants, including Prozac, is called selective serotonin reuptake inhibitors (SSRIs). These drugs allow more serotonin to be available for your nerve cells to use.
What Does Serotonin Do?
Serotonin affects many aspects of your gut function, including:
- It changes the motility of your bowels (how fast food moves through your system).
- It affects how much fluid, such as mucus, is secreted in your intestines.
- It affects how sensitive your intestines are to sensations like pain and fullness.
Differences in serotonin levels between individuals also line up with the differences between people who suffer from IBS. For example, people with IBS who have constipation often have lower-than-normal levels of serotonin. The muscles in their rectums are less reactive to serotonin, and they’re more likely to have hard or lumpy stools. Others with IBS who have diarrhea have been shown to have higher-than-normal levels of serotonin. Their rectums are more reactive: more likely to empty too early.
There are fourteen different kinds of receptors in your intestines that react in different ways to serotonin. Some receptors are responsible for sending messages to the brain that signal nausea, bloating, and pain. Other receptors change your sensitivity to or intensity of how distended or full your intestines feel.
Levels of each of these receptors vary from person to person. For example, your stomach may interpret what others perceive as a normal feeling of fullness, as pain.
Addressing Serotonin Issues
IBS patients have to deal with a cloud of symptoms, not all of which are related to the bowel. That’s because the effects of serotonin can extend to problems beyond your gut. For example, some studies suggest that those with low levels of serotonin may be more prone to fibromyalgia. Fibromyalgia is a heightened sensitivity to pain in muscles throughout the body. Altered levels of serotonin can also interrupt your sleep patterns and are associated with chronic depression and anxiety disorders.
The role of serotonin throughout the body can help explain the wide variety of symptoms you may be suffering, and may lead to more targeted therapies for different subtypes of IBS. Antidepressants and antianxiety medications haven’t shown to be highly effective in treating IBS. However, researchers are working on medications that are specifically designed to treat the serotonin changes seen in IBS without damaging side effects.
Talk with your doctor about current and emerging serotonin-related therapies that could address your specific symptoms. Don't forget that exercise and relaxation techniques like meditation can alter your serotonin levels enough to have a positive impact on your symptoms.