Melatonin supplements may help repair DNA damage associated with working night shifts, according to a small clinical trial published in . Occupational and environmental medicine.
The findings point to a potential way to counter one of the hidden biological effects of working all night. However, the researchers stress that larger studies are needed before they can recommend melatonin as a long-term strategy to reduce cancer risk in night shift workers.
Effects of night shifts on the body
Melatonin is best known as a hormone that helps regulate sleep. Stand up in the dark and let your body know it’s time to rest. For those who work all-nighters, that natural rhythm can be disrupted.
Normal nighttime melatonin production is often suppressed in night shift workers. Researchers say this may weaken the body’s ability to repair oxidative DNA damage, a type of cell wear and tear that occurs as part of normal metabolism.
This is important because reduced DNA repair may be one of the pathways that increases the risk of long-term night shifts and certain cancers. Night shifts have also received attention from leading health organizations for their effects on the body’s internal clock, sleep patterns, light exposure, and hormonal signaling.
Testing melatonin in night shift workers
To find out whether melatonin could improve DNA repair, researchers conducted a randomized, placebo-controlled trial of 40 night shift workers.
Half of the participants took 3 mg melatonin tablets once a day for four weeks. They took the supplements with meals during the day, about an hour before bedtime. The other half took a 3 mg placebo pill on the same schedule.
All participants worked at least two consecutive night shifts each week for at least 6 months. Each shift lasted at least 7 hours. None of the participants suffered from sleep disorders or long-term health conditions.
Markers of DNA repair rise during daytime sleep
Researchers collected urine samples during two study periods. One sample period occurred before the start of the study and the other near the end of the 4-week intervention. Samples were collected during daytime sleep after a night shift and during the following night shift.
Participants also wore activity trackers so researchers could measure how much sleep they got during the day.
The research team measured urinary levels of 8-OHdG, a marker used to assess oxidative DNA damage repair capacity. High urinary concentrations during sleep were interpreted as a sign of active repair activity.
Workers who took melatonin had 80% higher urinary 8-OHdG levels during daytime sleep compared to those who took a placebo. This suggests that melatonin may have promoted DNA repair while the participants slept after a night shift.
However, the same effect was not seen during subsequent night shifts. During that period, urinary 8-OHdG levels were not significantly different between the melatonin and placebo groups.
Why the findings matter
This study provides a possible explanation for how melatonin may help alleviate some of the biological burden caused by night work. The body normally uses sleep and circadian timing to coordinate repair processes. If people work all night and sleep during the day, the system may not be working as well as it should.
Melatonin may help restore some of the lost signals, at least during daytime sleep. Still, the study was small, short-term, and did not measure cancer outcomes. Only biomarkers related to DNA repair were measured.
Most of the participants were also healthcare workers, so this finding may not apply to all night shift workers. The researchers were also unable to account for exposure to natural light, which can affect melatonin levels in the body.
New background on night shift work
Since this trial was published in 2025, extensive research continues to reveal the complex effects of night shifts on health. Recent studies point to several possible mechanisms, including disrupted circadian rhythms, altered hormonal signaling, altered immune function, metabolic disruption, and impaired DNA repair.
Major scientific assessments have also addressed persistent night shifts and nighttime lighting 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 shifts and nighttime light to cancer risk.
These findings do not prove that melatonin supplements prevent cancer. Instead, they strengthen the rationale for studying whether restoring melatonin signaling can help alleviate some of the biological effects of long-term night shifts.
Researchers urge caution
The researchers stress that their findings should be validated in larger studies with different doses and longer follow-up periods.
They write, “Increased oxidative DNA damage due to decreased DNA repair capacity is a plausible mechanism that may contribute to the carcinogenic properties of night shift work. Our randomized, placebo-controlled trial suggested that melatonin supplementation may improve oxidative DNA damage repair capacity in night shift workers.”
And they conclude, “Our findings warrant future larger studies examining different doses of melatonin supplements and the long-term effects of melatonin use. Pending the results of such studies, melatonin supplements may prove to be a viable intervention strategy to reduce the burden of cancer in night shift workers.”
The researchers added: “People who work night shifts for many years need to take melatonin supplements continuously over that period to maximize their potential cancer prevention benefits, so it is important to assess long-term efficacy.”
So far, the results suggest that melatonin may do more than support sleep. It may also help night shift workers activate important repair processes while their bodies recover during the day. However, whether it will lead to meaningful long-term protection is an open question.
