Melatonin is a natural hormone that some people take as a supplement. It may help to regulate circadian rhythms, relieve pain, and improve gut barrier function. This means it may benefit people with irritable bowel syndrome (IBS).

This article discusses melatonin and IBS in more detail, including melatonin’s effectiveness in relieving IBS symptoms. It also explores possible side effects of melatonin and ways to manage IBS.

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Melatonin is a hormone produced by the pineal gland in the brain. It regulates circadian rhythms and the sleep-wake cycle by lowering body temperature and causing drowsiness.

However, according to an older study, the main concentration of melatonin is in the gastrointestinal tract (stomach, small intestines, and large intestine), surpassing the amount in the blood by 10–100 times. This suggests that melatonin may play an important role in the digestive system.

A 2017 study found that nighttime serum blood concentrations of melatonin in humans change over a person’s lifetime. Nocturnal melatonin levels are highest between ages 1–3 years, and decrease as a person grows older.

People can purchase melatonin as a dietary supplement. In the United States, the Food and Drug Administration (FDA) does not regulate melatonin.

The Rome IV, which doctors use to diagnose IBS, defines the condition as a disorder of gut-brain interaction. This means that it is related to how the brain and gut work together.

The criteria state that a person must have recurrent abdominal pain on average at least 1 day a week in the last 3 months. Pain is related to defecation or a change in the frequency or appearance of stool.

People may experience:

Doctors may also diagnose IBS according to its subtypes. The following subtypes of IBS are determined by the type of abnormal stool that a person has, ranging from watery diarrhea to hard, lumpy stool:

  • IBS with constipation (IBS-C)
  • IBS with diarrhea (IBS-D)
  • IBS with mixed bowel habits (IBS-M)
  • IBS unclassified (IBS-U, which indicates that a person’s bowel habits do not fall into the other categories)

Scientists are still investigating how melatonin may help to manage gastrointestinal conditions, including IBS.

According to a 2021 review, melatonin may be beneficial for IBS due to its analgesic effect, which may relieve abdominal pain.

Additionally, a 2022 study suggests that certain bacteria have “clock genes” controlled by circadian rhythms. Although scientists have not extensively studied this area, initial research indicates that restoring rhythms in sleep-wake cycles using melatonin may be an effective treatment for IBS.

The same study suggests that melatonin may help regulate the immune system and improve gut barrier function.

A 2017 review stated that low doses of melatonin accelerate intestinal transit time, which is the time food takes to travel through the intestines. However, high doses of melatonin may decrease gut motility, which refers to the movement of food through the digestive system.

The National Center for Complementary and Integrative Health (NCCIH) advises that there is not enough information about melatonin supplements to have a clear picture of their overall safety, particularly at higher doses. However, melatonin in the short term appears safe for most people.

The side effects of melatonin may include:

Melatonin may also interact with a person’s medication. The NCCIH advises that people with epilepsy or who are taking blood thinners should speak with a doctor before taking melatonin supplements.

The NCCIH also notes a 2017 study that tested 31 different melatonin supplements from stores and pharmacies. Most of the supplements did not contain the amount of melatonin listed on the label.

Additionally, 26% of the products contained serotonin. This could have harmful effects on some people or interact with certain medications, such as antidepressants.

Learn more about drug interactions here.

A person may prefer to try increasing their melatonin levels without taking supplements. People may help increase their melatonin levels by:

  • reducing their caffeine intake
  • exercising
  • eating tryptophan-rich foods
  • limiting their exposure to artificial light
  • safely spending time in the sun during the day

People should consider speaking with a healthcare professional for further information about increasing their melatonin levels naturally.

Learn more about natural melatonin here.

A doctor can advise a person on how to best manage their IBS. They may also prescribe medication if necessary.

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) explains that a doctor may recommend trying one of the following changes:

  • eating more fiber (including whole grains, oat products, and beans)
  • avoiding gluten (including wheat and rye products)
  • following a low FODMAP diet that excludes specific foods containing carbohydrates that may be hard to digest

Additionally, the NIDDK advises that the following lifestyle changes may help a person manage IBS symptoms:

A probiotic supplement may help to balance the bacteria in the gut, which may relieve symptoms of IBS. However, a person should consider speaking with a doctor before taking probiotic supplements.

A doctor may also recommend mental health therapies such as:

Melatonin has properties that may help to ease the symptoms of IBS. It regulates circadian rhythms and may help improve sleep and immune function in the gut, and ease pain.

However, scientists are still investigating how melatonin may help manage gastrointestinal disorders.

Melatonin may not be suitable for some people. It can interact with some medications, so a person should always talk with a doctor before taking it.