Melatonin and IBS: Is It the Supplement or the Sleep?

Ask your caseload how they sleep, and you'll hear one supplement more than any other: melatonin. Most patients take it for one reason — to fall asleep. A recent meta-analysis suggests it may be doing more than that, especially for patients living with irritable bowel syndrome (IBS).

What the research found

Themeta-analysis pooled randomized trials of melatonin in adults with IBS. In two of the four studies included, patients reported improved IBS symptoms while taking 3 to 6 mg of melatonin daily. Treatment periods ranged from two to eight weeks, depending on the study.

That's a small evidence base, and the protocols varied. But the signal is interesting enough to deserve a closer look — and more research.

The big question: gut or sleep?

Here's what I keep coming back to. Is melatonin acting directly on the gut? Or is better sleep the real driver, improving the gut microbiome and overall gut health downstream?

Both paths are plausible. Melatonin is produced in large amounts in the gastrointestinal tract, not only the brain. Poor sleep is also closely tied to gut symptoms. The answer matters, because it changes what we screen for and how we talk to patients about sleep, digestion and recovery.

Why this matters in the clinic

IBS often travels with the problems PTs treat every day: chronic pain, pelvic floor dysfunction, low back pain, fatigue and poor sleep. Patients rarely separate these issues — and we shouldn't either.

A few practical takeaways:

• Ask about supplements at intake. Many patients won't mention melatonin unless asked.
• Screen sleep and GI symptoms together. Each can shape pain, recovery and participation in rehab.
• Stay in scope. Share the evidence, then refer patients to their physician or a registered dietitian before they start or change a supplement.

Join the conversation

I'd love to hear from you. Have you or your patients with IBS noticed a difference with melatonin? Share your experience in the comments.

Go deeper with Course 3

The gut–sleep–pain connection is exactly the kind of topic we unpack in Course 3 of our 3-part Nutritional Physical Therapy certificate series. Each course is built for PTs who want evidence-based nutrition tools they can use with patients — while earning continuing education credit.