The Role of Serotonin
More biology: The means by which one nerve cell communicates with the next is through chemicals called neurotransmitters. An extremely important neurotransmitter for digestive functioning is serotonin (5-HT). It is estimated that up to 95% of the serotonin in the human body is found in the digestive tract. Serotonin is considered to be a vital part of the communication system between the brain and the gut. Serotonin seems to play a part in motility, sensitivity, and secretion of fluids. Movement, pain sensitivity and the amount of fluid in the stool – you can see why serotonin has been a focus for IBS researchers!Differences have been found in serotonin levels between patients who suffer from diarrhea vs. those who suffer from constipation. Patients with diarrhea had higher than normal levels of serotonin in their blood following a meal, while patients who suffered from constipation had lower than normal levels of serotonin. This difference underlies the efforts to develop medication that either increases or decreases serotonin levels by targeting specific receptor sites (5-HT3 and 5-HT4) to treat IBS. Both of the following medications are currently on the market, but have strict restrictions on their use in order to prevent serious negative side effects:
- Lotronex -- a 5-HT3 blocker for treatment of diarrhea
- Zelnorm – a 5-HT4 stimulant for treatment of constipation
Knowledge is Power
How can you translate your new knowledge into helping to better manage your IBS? Obviously, we don’t have the power to directly affect our serotonin levels. However, there are two areas where our actions have a direct impact on the communication system between the brain and the gut. Through the use of relaxation exercises, you can actively work to turn off the stress response, in which gut changes come about in response to thoughts and feelings. You could also consider the gastrocolic reflex in which colon contractions are stimulated by eating a large meal or fatty foods, when deciding what foods to eat. For diarrhea, it would be better to eat smaller meals, while for constipation, a large meal would be preferable to trigger a bowel movement.The understanding that the problems in IBS extend way beyond having a “sensitive stomach” can help you to develop a variety of strategies for addressing these very problems.
Sources:
Aggarwal, A., Cutts, T.F., Abell, T.L., Cardoso, S., Familoni, B., Bremer, J., & Karas, J. “Predominant symptoms in irritable bowel syndrome correlate with specific autonomic nervous system abnormalities.” (1994) Gastroenterology 106:1114-1118.
Baker, D.E. “ Rationale for using serotonergic agents to treat irritable bowel syndrome” (2005) American Journal of Health-System Pharmacy 62:700-711.
Mayer, E.A., Tillisch, K. & Bradesi, S. "Modulation of the Brain-Gut Axis as a Therapeutic Approach in Gastrointestinal Disease” (2006) Alimentary Pharmacology & Therapeutics 24:919-933.
Norton, W. & Drossman, D. “Symposium Summary Report” (2007)
Digestive Health Matters16:4 -7.
Schmulson, M. J. “Brain-Gut Interaction in Irritable Bowel Syndrome: New Findings of a Multicomponent Disease Model” (2001) The Israel Medical Association Journal 3:104-109.
Further Reading:
