Scientists Identify New Benefits of Melatonin Supplementation

Researchers say that larger studies examining varying doses and long-term effects are now warranted.

A small clinical trial, published in Occupational & Environmental Medicine, suggests that melatonin supplementation may help counteract DNA damage linked to night shift work by enhancing the body’s ability to repair it.

The researchers emphasize the need for larger studies to explore different dosages and assess the potential long-term effects of melatonin supplementation.

Night shift workers experience suppressed nighttime production of melatonin, a key hormone regulating the body’s internal clock. This suppression weakens the body’s ability to repair oxidative DNA damage—a natural byproduct of cellular processes—potentially increasing the risk of certain cancers.

To investigate whether melatonin supplementation could mitigate this damage by improving DNA repair, the researchers conducted a study involving 40 night shift workers.

Study Design and Methodology

Half the participants were randomly assigned to a daily 3 mg melatonin pill taken with food and an hour before going to sleep during the day for 4 consecutive weeks. And half were randomly assigned to a 3 mg dummy pill following the same schedule.

All the participants worked a minimum of two consecutive night shifts every week, lasting at least 7 hours a night, for at least 6 months. None had any sleep disorders or long-term conditions.

Urine specimens were collected during the second of two subsequent day sleep and night shift periods—once before starting the trial and once near the end of the 4 weeks.

Participants wore activity trackers to measure how long they slept during the day. Levels of 8-OHdG, which is an indicator of DNA damage repair capacity, were measured in all urine passed during periods of daytime sleep and the subsequent night shift.

Urinary levels of 8-OH-dG were 80% higher during daytime sleep—indicating better repair— among those taking the melatonin supplement than those taking the dummy pill. But there was no significant difference in urinary 8-OH-dG levels during the subsequent night shift.

This is a small study, and most of the participants worked in healthcare, so the results may not be applicable to other types of night shift worker, acknowledge the researchers. Nor were they able to account for natural light exposure, which affects circulating melatonin levels.

Future Research and Potential Implications

But they point out: “Increased oxidative DNA damage due to diminished DNA repair capacity is a compelling mechanism that may contribute to the carcinogenicity of night shift work. Our randomized placebo-controlled trial suggested melatonin supplementation may improve oxidative DNA damage repair capacity among night shift workers.”

And they conclude: “Our findings warrant future larger-scale studies that examine varying doses of melatonin supplements and longer-term impacts of melatonin use. Pending the outcome of such studies, melatonin supplementation may prove to be a viable intervention strategy to reduce the burden of cancer among night shift workers.”

They add: “Assessing long-term efficacy is critical since those who work night shifts for many years would need to consistently consume melatonin supplements over that time frame to maximize the potential cancer prevention benefits.”

Reference: “Melatonin supplementation and oxidative DNA damage repair capacity among night shift workers: a randomised placebo-controlled trial” by Umaimah Zanif, Agnes S Lai, Jaclyn Parks, Aina Roenningen, Christopher B McLeod, Najib Ayas, Xiangtian Wang, Yan Lin, Junfeng (Jim) Zhang and Parveen Bhatti, 24 February 2025, Occupational and Environmental Medicine.
DOI: 10.1136/oemed-2024-109824

Funding: The Canadian Cancer Society and the Canadian Institutes of Health Research-Institute of Cancer Research in partnership with the Cancer Research Society and the BC Cancer Foundation.