Melatonin supplements could help the body repair DNA damage associated with night work. This is according to a small clinical study published in the journal Occupational & Environmental Medicine. The results point to a possible way to counteract one of the hidden biological effects of night work. However, the researchers emphasize that more extensive studies are needed before melatonin can be recommended as a long-term strategy to reduce the risk of cancer in night workers.
How Night Shifts Unbalance the Body
Melatonin is a hormone produced naturally in the body, mainly in the pineal gland (pineal gland) in the brain. It plays a central role in controlling the sleep-wake rhythm and serves as a biological signal to the body for the night. As soon as it gets dark, melatonin production increases. This informs the body that the active phase of the day has ended and regeneration processes should begin. Towards morning, when light hits the retina, melatonin production decreases again and the body adjusts to wakefulness and activity.
However, melatonin does not only act as a “sleep hormone”. In recent years, research has shown that it fulfills numerous other functions in the body. For example, melatonin influences the immune system, energy metabolism, inflammatory processes and the regulation of various hormones. It also has antioxidant properties. This means that melatonin can help to neutralize so-called free radicals – highly reactive molecules that can damage cells and their genetic material. There is also evidence that melatonin supports processes involved in the recognition and repair of DNA damage .
In people who regularly work nights, this finely tuned system is often out of balance. During the night shift, employees are exposed to artificial light, even though the body is biologically adjusted to darkness. Even relatively small amounts of light can significantly inhibit melatonin production. As a result, the body receives contradictory signals: the internal clock expects rest and regeneration, while the person stays awake and works.
This disruption of the natural day-night rhythm is known as circadian maladjustment. It not only affects sleep, but also numerous biological processes. Studies show that night shift workers are more likely to suffer from sleep deprivation, chronic fatigue, concentration problems and metabolic disorders. Changes in hormone regulation, the immune system and cardiovascular function are also associated with long-term shift work.
Investigation of Melatonin in Night Workers
Of particular interest is the possible role of melatonin in the repair of oxidative DNA damage. Such damage occurs continuously as part of normal metabolism, but can be exacerbated by stress, inflammation or other stresses. Normally, the body has effective repair mechanisms to eliminate this damage. However, some scientists suspect that the chronically reduced melatonin production in night workers could impair these repair processes. As a result, more DNA damage could accumulate over many years, which could theoretically contribute to the development of certain types of cancer.
Against this background, long-term night work has attracted the attention of international health organizations. The International Agency for Research on Cancer, an agency of the World Health Organization, classifies night work, which is associated with disruption of the circadian rhythm, as “probably carcinogenic to humans”. This classification is based on a combination of epidemiological studies, animal experiments and biological findings on the effects of light at night, sleep disturbance and reduced melatonin production. The current study sheds light on whether the intake of melatonin by night shift workers can help to restore at least some of the repair processes impaired by the disturbed internal clock.
To investigate whether melatonin could improve DNA repair, the researchers conducted a randomized, placebo-controlled study with 40 night workers. Half of the participants took a 3 mg melatonin tablet once a day for 4 weeks. They took the preparation about 1 hour before going to bed during the day together with a meal. The other half took a 3 mg placebo tablet on the same schedule. All participants had worked at least two consecutive night shifts every week for at least 6 months. Each shift lasted at least 7 hours. None of the participants suffered from sleep disorders or chronic illnesses.
A Marker for DNA Repair Increased During Daytime Sleep
The researchers collected urine samples during two study periods. One sample period took place before the start of the study, the other towards the end of the 4-week intervention. The samples were taken during daytime sleep after the night shift and during the following night shift. The participants also wore activity trackers so that the researchers could measure how long they slept during the day. The team measured urinary 8-OHdG concentrations, a marker used to assess the repair capacity of oxidative DNA damage. Higher urine concentrations during sleep were interpreted as a sign of greater repair activity.
In workers taking melatonin, urinary 8-OHdG levels during daytime sleep were 80% higher than in those taking the placebo. This suggests that melatonin may have promoted DNA repair while participants slept after night work. However, the same effect was not observed during the following night shift. During this period, urinary 8-OHdG levels did not differ significantly between the melatonin and placebo groups.
Why the Results are Important
The study provides an interesting indication of how melatonin could help to mitigate some of the biological stresses of night work. Normally, the body uses the night and sleep to coordinate important regeneration and repair processes. This includes mechanisms that recognize and repair damage to DNA. In people who regularly work nights, this finely tuned system can be disrupted by the shift in the sleep-wake cycle and exposure to light at night.
Since melatonin plays a central role in controlling the internal clock and also has antioxidant properties, researchers suspect that supplementation could help restore some of these disrupted signals. The results of the study support this assumption, as participants taking melatonin during daytime sleep showed increased activity of a marker associated with the repair of oxidative DNA damage.
At the same time, the results should be interpreted with caution. The study was relatively small with only 40 participants and lasted only four weeks. In addition, no clinical endpoints such as cancer, disease or general health were examined. Only a biomarker was measured, which provides indications of repair processes but does not constitute direct evidence of a health benefit.
Another important point is the limited transferability of the results. Most of the participants worked in the healthcare sector, so it remains unclear whether similar effects would also occur in other occupational groups with night work. In addition, factors such as individual light exposure outside of work, sleeping habits or lifestyle differences could not be fully taken into account. Larger and longer-term studies are therefore needed to clarify whether the observed biological effects actually lead to a lower risk of disease or cancer in the long term.
Recent Context on Night Work
Since the publication of the study in 2025, further research has confirmed the complex effects of night work on health. The focus is on the disruption of the circadian rhythm – the body’s internal clock that controls sleep, hormone balance, metabolism, immune function and important repair processes. Regular night work and exposure to light at night can have a lasting effect on these processes.
Scientists are discussing several possible mechanisms by which night work could increase health risks. These include reduced melatonin production, changes in hormone regulation, metabolic disorders, chronic inflammatory processes, altered immune function and impaired DNA repair. These factors could contribute to the development of various diseases in the long term.
The International Agency for Research on Cancer, an institution of the World Health Organization, has classified night work with circadian disturbances as “probably carcinogenic to humans”. The National Toxicology Program also sees evidence of a link between long-term night work, exposure to light at night and an increased risk of cancer.
However, the findings to date do not prove that melatonin supplements prevent cancer. Rather, they provide a scientific basis for the assumption that restoring natural melatonin signaling could mitigate some of the biological consequences of night work. Whether this actually leads to long-term health protection remains to be seen in larger, longer-term studies.
Study Provides Cncouraging Results
The researchers emphasize that their results should be verified in larger studies with different doses and longer follow-up periods. They write: “Increased oxidative DNA damage due to reduced DNA repair capacity is a compelling mechanism that could contribute to the carcinogenicity of night work. Our randomized, placebo-controlled trial suggests that melatonin supplementation may improve the repair capacity for oxidative DNA damage in night workers.”
And they conclude: “Our results warrant future large-scale studies investigating different doses of melatonin supplements and the longer-term effects of melatonin intake. Pending the results of such studies, melatonin supplementation may prove to be a viable intervention strategy to reduce the cancer burden in night workers.” They add: “Evaluation of long-term efficacy is critical, as individuals who work the night shift for many years would need to take melatonin supplements consistently over this period to maximize the potential cancer prevention benefits.”
Currently, the results suggest that melatonin could do more than just aid sleep. It could also help night shift workers activate an important repair process while their bodies recover during the day. Whether this leads to significant long-term protection remains an open question.