Sleep supplement melatonin could increase gut inflammation

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Melatonin, a hormone often taken as a sleep aid supplement, can potentially worsen inflammation of the intestine and impair the action of gut bacteria, according to a study published in the journal Microorganisms.

The gut microbiota helps control digestion, benefiting the immune system.

An imbalance of unhealthy and healthy microbes in the intestines may contribute to disorders such as weight gain, high blood sugar, and above-normal cholesterol.

Melatonin’s Negative Effect on the Intestine

Melatonin is popularly known as the “sleep hormone” and is often taken without a doctor’s prescription by people with sleep problems.

However, the study shows that the ingestion of melatonin supplements can have adverse effects on health, despite its antioxidant effects and role in regulating sleep cycles.

The lead author of the study, Cristina Ribeiro de Barros Cardoso, a professor of immunology and neuroimmunoendocrinology at the University of São Paulo’s Ribeirão Preto School of Pharmaceutical Sciences in Brazil, says, “Our review found that people should be careful about taking hormone supplements.”

Cardoso’s laboratory researches inflammatory bowel disorders, including Crohn’s disease and ulcerative colitis.

Treatment entails suppressing or inhibiting the immune response to reduce excessive inflammation that damages the intestine.

The treatment may involve immunobiological medications, which are more effective for moderate and severe cases but are unaffordable for most patients.

In Brazil, they are paid for only under specific circumstances by the national health service or by health plans in the event of a court order.

Melatonin’s Effects on Inflammation of the Intestine

The study involved an experiment in which colitis was induced in mice, and they were treated with melatonin. Their condition became worse instead of improving.

“It’s important to stress that no human patients were involved in the study. The animals’ bowel inflammation became much, much worse,” Cardoso said.

The negative effect of melatonin depends on the bacteria that live in the intestine and are also associated with inflammatory diseases of the region.

Certain features of gut microbiota increase inflammation and dysregulate the immune system in response to treatment with melatonin, damaging the digestive system.

Regulation and Risks of Melatonin Supplements

ANVISA, Brazil’s national health surveillance agency, has updated its information and rules on the sale of melatonin as a food supplement. However, control is looser than for medications.

“It’s important to stress this because we talk about the need to take care, but people may think, ‘Oh, but I’ll just pop into the pharmacy and buy some, it’s been approved by ANVISA.’

True, but only when labeled as a food supplement, and what we’re asking in the study is whether it’s really a mere food supplement. What are the risks?” Cardoso said.

Overall, people should be cautious about taking hormone supplements or food supplements, Cardoso said.

“It’s a hormone, and regulation of the interaction between all hormones and the immune system is very delicate.”

If you care about nutrition, please read studies that eating nuts may help reduce risks of the gut lesion and cancer, and how tea and coffee influence your risk of high blood pressure.

For more information about nutrition, please see recent studies that anti-inflammatory diet could help prevent fatty liver disease, and vitamin D could help lower the risk of autoimmune diseases.

The study was published in Microorganisms.

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