Melatonin And Irritable Bowel Syndrome

G. Douglas Andersen, DC, DACBSP, CCN

Melatonin is involved in the regulation of the sleep-wake cycle, circadian rhythms, and seasonal changes in the light dark cycle. Commonly used to induce sleep, some (but not all) find it to reduce jet lag. There is a high concentration of melatonin in the pineal gland, where it is manufactured. I was surprised to learn that there are significant amounts of melatonin present in the gastrointestinal tract. Apparently melatonin helps regulate gastrointestinal motility.1

Melatonin Synthesis

Those of you who do more than a site-specific history are well aware of the number of people who suffer from irritable bowel syndrome (IBS). Epidemiological studies performed in the United States, the United Kingdom, and China show that IBS affects almost 1 in 5 people.2

The exact cause of irritable bowel syndrome is unknown. It is called a syndrome because it causes a wide range of symptoms that range from gas, bloating, and pain to constipation and diarrhea. Excessive stress, (either emotional or physical) can trigger flare-ups as can the wrong foods, hormonal variations, and even changes in activity patterns. A patient who has IBS and is sensitive to and/or allergic to a specific food can run the risk of exacerbating his/her condition. The most common foods that affect IBS include grains, alcohol, caffeine, chocolate, dairy, and carbonated beverages.3 However, any food a person has difficulty with can provoke symptoms. In some people, simply eating a large meal can trigger IBS.

Recently, there were 2 papers, both of which came from doctors in Singapore that have linked melatonin with irritable bowel syndrome.4, 5 When studying the etiology of irritable bowel syndrome in the year 2000, it was discovered to be more common in night-shift nurses than day-shift nurses.6 This finding lead to a pair of double blind, placebo-controlled studies. The first involved 17 women3 and the second had 40 patients (24 female and 16 male).5 In Lu et. al, 4 women were given 3 mg of melatonin at bedtime or a placebo for 8 weeks, followed by a 4-week washout period. Then the women received the opposite treatment for a second 8 weeks. In the Song, et al. study,5 the subjects were given either 3 mg of melatonin or a placebo at bedtime for 2 weeks, followed by a washout period, and then 2 more weeks of reversed treatment. The results of both studies showed that melatonin reduced the degree of IBS symptoms, especially abdominal pain and bloating. Curiously melatonin did not affect sleep scores in either study. It also did not affect anxiety, depression, stool type or stool frequency.

Although larger and longer studies are needed, melatonin may be worth a try for IBS patients- especially for those who have had unsatisfactory or unsuccessful results with other approaches.

Treatment Strategies for IBS

Symptom Therapy
Constipation Increase dietary fiber, fluids and activity
Diarrhea Rule out food allergy/hypersensitivity
Reduce fiber during flare ups
Pain/gas Try digestive enzymes with meals. Identify and eliminate intolerable foods, especially fermentable carbohydrates. Consider a trial of melatonin.


11 Bebeuik, G.A., Pang S.F., The Role of Seratonin and Melatonin in some parameters of Gastrointestinal Activity; Ontogency, Some Regulation of Food, and Mutual Seratonin-Melatonin Feedback. J. Pineal Res. 1994; 16: 91-99.
22 National Digestive Diseases Information Clearing House (NDDIC).
33 National Digestive Diseases Information Clearing House (NDDIC).
44 Lu, W.Z., Gwee, K.A., Moochhala, S.M., Ho, K.Y. Melatonin Improves Bowel Symptoms in Female Patients with Irritable Bowel Syndrome: a Double-Blind, Placebo-Controlled Study. Aliment Pharmacol Ther. 2005; 22: 927-934.
55 Song G.H., Leng, P.H., Gwee K.A., et al. Melatonin Improves Abdominal Pain in Irritable Bowel Syndrome Patients Who Have Sleep Disturbances: a Randomized, Double-Blind, Placebo-Controlled Study. Gut. 2005; 54: 1402-1407.
66 Lu, W.Z., Ho, K.Y., Moochhala, S.M., et al. Bowel Symptoms are Related to Sleep Disturbances in Shift Nurses. Gut. 2000; 47A: 40.


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Copyright 2004-2007, G. Douglas Andersen, DC, DACBSP, CCN, 916 E. Imperial Hwy, Brea, CA 92821, (714) 990-0824