Melatonin supplements may help the body repair DNA damage linked to night shift work, according to a small clinical trial published in Occupational & Environmental Medicine.
The findings point to a possible way to counter one of the hidden biological effects of working through the night. However, the researchers stress that larger studies are needed before melatonin can be recommended as a long-term strategy for reducing cancer risk in night shift workers.
How Night Shifts Disrupt the Body
Melatonin is best known as the hormone that helps regulate sleep. It rises in darkness and signals to the body that it is time to rest. For people who work overnight, that natural rhythm can be disrupted.
Normal night-time melatonin production is often suppressed in night shift workers. According to the researchers, this may weaken the body’s ability to repair oxidative DNA damage, a type of cellular wear and tear that occurs as part of normal metabolism.
That matters because reduced DNA repair may be one pathway linking long-term night shift work with higher risk for certain cancers. Night shift work has also drawn attention from major health agencies because of its effects on the body’s internal clock, sleep patterns, light exposure, and hormone signaling.
Testing Melatonin in Night Shift Workers
To explore whether melatonin could improve DNA repair, researchers conducted a randomized placebo controlled trial involving 40 night shift workers.
Half of the participants took a 3 mg melatonin pill once daily for 4 weeks. They took the supplement with food about 1 hour before going to sleep during the day. The other half took a 3 mg placebo pill on the same schedule.
All participants had been working at least two consecutive night shifts each week for at least 6 months. Each shift lasted at least 7 hours. None of the participants had sleep disorders or long-term health conditions.
A Marker of DNA Repair Rose During Daytime Sleep
The researchers collected urine samples during two study periods. One sample period took place before the trial began, and the other occurred near the end of the 4 week intervention. Samples were collected during daytime sleep after night shift work and during the following night shift.
Participants also wore activity trackers so the researchers could measure how long they slept during the day.
The team measured urinary levels of 8-OHdG, a marker used to assess oxidative DNA damage repair capacity. Higher urinary levels during sleep were interpreted as a sign of greater repair activity.
Among workers who took melatonin, urinary 8-OHdG levels were 80% higher during daytime sleep compared with those who took the placebo. That suggests melatonin may have boosted DNA repair while participants were sleeping after night work.
However, the same effect was not seen during the subsequent night shift. During that period, urinary 8-OHdG levels did not differ significantly between the melatonin and placebo groups.
Why the Findings Matter
The study offers a possible explanation for how melatonin might help reduce some of the biological strain caused by working at night. The body normally uses sleep and circadian timing to coordinate repair processes. When people work overnight and sleep during daylight hours, that system may not function as well.
Melatonin may help restore part of that lost signal, at least during daytime sleep. Still, the study was small and short, and it did not measure cancer outcomes. It only measured a biomarker related to DNA repair.
Most participants also worked in healthcare, which means the results may not apply to all night shift workers. The researchers were also unable to account for natural light exposure, which can affect melatonin levels in the body.
Newer Context on Night Shift Work
Since the trial was published in 2025, broader research has continued to highlight the complex ways night shift work may affect health. Recent reviews have pointed to several possible mechanisms, including circadian disruption, altered hormone signaling, changes in immune function, metabolic disruption, and impaired DNA repair.
Major scientific assessments have also treated persistent night shift work and light at night as important public health concerns. The International Agency for Research on Cancer has classified night shift work as probably carcinogenic to humans, and the National Toxicology Program has reviewed evidence linking persistent night shift work and light at night with cancer risk.
These findings do not prove that melatonin supplements prevent cancer. Instead, they strengthen the rationale for studying whether restoring melatonin signaling could help reduce some of the biological effects of long-term night work.
Researchers Urge Caution
The researchers emphasize that their findings should be tested in larger studies involving different doses and longer follow up periods.
They write: “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.”
For now, the results suggest that melatonin may do more than support sleep. It may also help night shift workers activate a key repair process while their bodies recover during the day. But whether that translates into meaningful long-term protection remains an open question.
