Study Finds Melatonin, a Popular Sleep Supplement, Can Disrupt Gut Health

by Hiroshi Tanaka

Recent research published in the journal Microorganisms highlights the potential adverse effects of melatonin, a widely used sleep supplement, on gut health. Despite being known for its antioxidant properties and role in regulating sleep cycles, melatonin may exacerbate intestinal inflammation and disrupt the delicate balance of gut microbiota, which is essential for digestion, immunity, and overall well-being. Professor Cristina Ribeiro de Barros Cardoso warns individuals about the potential health risks associated with melatonin supplementation.

The study conducted experiments on laboratory mice and revealed that melatonin intake intensified symptoms of Crohn’s disease and ulcerative colitis, two types of inflammatory bowel disorders. However, the impact of melatonin varied depending on the mice’s gut microbiota profile.

The gut microbiota, a complex ecosystem of bacteria and other microbes, plays a critical role in maintaining good health by aiding digestion and supporting the immune system. An imbalance in this microbial community can contribute to various health issues, including weight gain, elevated blood sugar levels, abnormal cholesterol levels, and other disorders.

Melatonin, commonly referred to as the “sleep hormone,” is frequently used as a dietary supplement without medical supervision by individuals experiencing sleep problems. Despite its perceived harmlessness, Professor Cardoso emphasizes that melatonin supplements can have adverse effects on health.

“We often assume it’s harmless because it helps regulate sleep as a hormone. However, our study shows that people need to be cautious when taking hormone supplements, as melatonin supplementation can potentially harm their health,” explains Cristina Ribeiro de Barros Cardoso, an immunology and neuroimmunoendocrinology professor at the University of São Paulo’s Ribeirão Preto School of Pharmaceutical Sciences.

Inflammatory bowel disorders like Crohn’s disease and ulcerative colitis result from an overreactive immune response, leading to damage to the gut microbiome and severe symptoms such as abdominal pain, persistent diarrhea, bleeding, and fatigue. Treatment typically involves suppressing or inhibiting the immune response to reduce inflammation. However, advanced treatments such as corticosteroids, immunosuppressants, or immunobiological medications are often expensive and inaccessible to most patients.

Cardoso’s laboratory focuses on gaining a better understanding of these diseases and developing more affordable treatment options. They initially explored melatonin as a potential novel treatment for inflammatory bowel disorders but discovered that it had the opposite effect. Consequently, patients need to be aware of the potential dangers associated with melatonin supplementation.

The study involved inducing colitis in mice and treating them with melatonin. Surprisingly, their condition worsened instead of improving. “It’s crucial to emphasize that no human patients were involved in the study. The inflammation in the animals’ bowels significantly intensified,” clarifies Cardoso.

Further investigation revealed that melatonin’s negative impact depended on the bacteria residing in the intestines, which are also associated with inflammatory diseases in the region. Specific characteristics of gut microbiota can increase inflammation and disrupt the immune system’s regulation when exposed to melatonin, leading to damage in the digestive system.

Cardoso warns against assuming the safety of medications, hormone supplements, or hormones marketed as food supplements. Purchasing a “food supplement” from a pharmacy might give the impression that it is harmless and won’t alter the body, but melatonin is a hormone, and the interaction between hormones and the immune system is delicate.

Although Brazil’s national health surveillance agency, ANVISA, has updated information and regulations regarding the sale of melatonin as a food supplement, its control is less strict compared to medications. People should be cautious and not assume that melatonin is risk-free solely because it is approved by ANVISA for sale as a food supplement.

The study is part of a project led by Cardoso and funded by FAPESP, aiming to provide novel and more affordable treatment options for inflammatory bowel disorders.

Frequently Asked Questions (FAQs) about melatonin, gut health

Q: What is the research about melatonin and gut health?

A: The research focuses on the potential adverse effects of melatonin, a popular sleep supplement, on gut health. It reveals that melatonin can exacerbate intestinal inflammation and disrupt the balance of gut microbiota, which are crucial for digestion, immunity, and overall health.

Q: What role does gut microbiota play in the body?

A: Gut microbiota refers to the community of bacteria and other microbes residing in our intestines. They play a vital role in maintaining good health by aiding in digestion, enhancing the immune system, and contributing to overall well-being.

Q: How is melatonin commonly used?

A: Melatonin is widely used as a dietary supplement to regulate sleep. Many individuals take melatonin without a physician’s approval to address sleep problems.

Q: What are the potential adverse health effects of melatonin supplementation?

A: The study suggests that melatonin supplementation can potentially worsen intestinal inflammation, particularly in individuals with inflammatory bowel disorders such as Crohn’s disease and ulcerative colitis. It emphasizes the importance of caution when taking hormone supplements like melatonin.

Q: Can melatonin disrupt the immune system?

A: Melatonin, when interacting with specific gut microbiota, may dysregulate the immune system’s response, leading to damage in the digestive system. Imbalance in gut microbiota can result in inflammation and affect the immune system’s regulation.

Q: Should I be concerned about the quality and regulation of melatonin supplements?

A: The study raises concerns about the potential risks of melatonin supplements and highlights the need for caution. Although regulatory agencies like ANVISA have guidelines for the sale of melatonin as a food supplement, control is less strict compared to medications. It is important to be aware of the potential dangers and consult with healthcare professionals before taking any supplements.

More about melatonin, gut health

  • Study: “The Microbiota-Dependent Worsening Effects of Melatonin on Gut Inflammation”

  • University of São Paulo’s Ribeirão Preto School of Pharmaceutical Sciences (FCFRP-USP)

  • ANVISA (Brazil’s national health surveillance agency)

  • FAPESP (São Paulo Research Foundation)

You may also like


SleepyJoe July 9, 2023 - 11:58 pm

wow i didn’t know melatonin can mess up gut health! that’s crazy! it’s like, you think it’s good for sleep but then it’s bad for your digestion and stuff? mind blown!

HealthNut22 July 10, 2023 - 1:54 am

omg, this is so important! I always thought melatonin was harmless cuz it’s like a “food supplement,” you know? But now I’m shook! Gotta be careful with what we put in our bodies, even if it’s sold at the pharmacy!

ScienceGeek88 July 10, 2023 - 4:45 am

Fascinating study! Gut microbiota is such a hot topic in research nowadays, and it’s interesting to see how melatonin can affect it. Makes you wonder what other supplements might have hidden risks. Kudos to Professor Cardoso and her team for shedding light on this!

SleeplessSleeper July 10, 2023 - 8:19 am

Wait, melatonin can make gut problems worse? That’s not what I signed up for! I just wanted a good night’s sleep, not an upset tummy. Time to rethink my sleep routine and maybe find some other sleep aids that won’t mess with my gut.

HealthyBalance July 10, 2023 - 10:56 pm

It’s scary how something as simple as a sleep supplement can have unintended consequences. We need to be more mindful of what we put in our bodies and do our research. Thanks for sharing this eye-opening study!


Leave a Comment

* By using this form you agree with the storage and handling of your data by this website.

SciTechPost is a web resource dedicated to providing up-to-date information on the fast-paced world of science and technology. Our mission is to make science and technology accessible to everyone through our platform, by bringing together experts, innovators, and academics to share their knowledge and experience.


Subscribe my Newsletter for new blog posts, tips & new photos. Let's stay updated!

© 2023 SciTechPost