Can melatonin cause diarrhea
Pro Research Analysisby 
Searched over 200M research papers
Can Melatonin Cause Diarrhea?
Introduction to Melatonin and Gastrointestinal Effects
Melatonin, a hormone primarily known for regulating sleep-wake cycles, has various effects on the gastrointestinal (GI) system. It is produced not only by the pineal gland but also by enterochromaffin cells in the digestive tract, where it plays a role in regulating gut motility and local anti-inflammatory responses . However, its impact on the GI system can sometimes lead to adverse effects, including diarrhea.
Case Study: Melatonin-Induced Diarrhea
A notable case involved a 49-year-old woman who experienced diarrhea after taking an herbal product containing melatonin for insomnia. She had 3-4 liquid bowel movements per day, which ceased when she stopped taking melatonin. Upon resuming melatonin, her symptoms reappeared, confirming a direct correlation between melatonin intake and diarrhea . This case highlights that melatonin can indeed cause diarrhea in some individuals.
Melatonin and Irritable Bowel Syndrome (IBS)
Research on melatonin's effects on IBS, particularly in postmenopausal women, provides mixed results. In a study involving 80 postmenopausal women with IBS, melatonin was administered to evaluate its impact on IBS symptoms. While melatonin showed beneficial effects in patients with constipation-predominant IBS, its effects on diarrhea-predominant IBS were not significantly better than a placebo . This suggests that while melatonin may help some IBS symptoms, it does not universally alleviate diarrhea and may not be suitable for all IBS patients.
Protective Effects Against Chemotherapy-Induced Diarrhea
Interestingly, melatonin has shown protective effects against chemotherapy-induced enteritis in rats. Methotrexate, a chemotherapy drug, often causes severe intestinal damage and diarrhea. Melatonin administration in this context helped mitigate these effects, suggesting its potential in protecting the gut lining and reducing diarrhea caused by chemotherapy . This indicates that melatonin's impact on diarrhea can vary depending on the underlying cause.
Melatonin and Sleep Deprivation-Induced Intestinal Dysfunction
In another study, melatonin supplementation in sleep-deprived mice helped reverse intestinal barrier dysfunction and microbiota dysbiosis, which are often associated with diarrhea. This protective effect was attributed to melatonin's antioxidant properties and its ability to modulate inflammatory responses . This further supports the idea that melatonin's effects on the GI system are complex and context-dependent.
Conclusion
While melatonin can cause diarrhea in some individuals, particularly when taken in high doses or without medical supervision, it also has protective effects in certain contexts, such as chemotherapy-induced enteritis and sleep deprivation-induced intestinal dysfunction. Therefore, the relationship between melatonin and diarrhea is multifaceted and warrants careful consideration of individual circumstances and underlying health conditions. If you experience diarrhea after taking melatonin, it is advisable to consult a healthcare provider to adjust the dosage or explore alternative treatments.
Sources and full results
Most relevant research papers on this topic