The sleep hormone melatonin also helps repair DNA damage

Damage to cellular DNA can lead to impaired cell function, cell death, accelerated aging, and mutations that, in the worst case, may develop into cancer. Fortunately, the body has an advanced repair system that continuously corrects DNA damage. New research even suggests that melatonin plays an important role in repairing DNA damage while we sleep.
This finding comes from a placebo-controlled Canadian study of shift workers who took melatonin supplements to compensate for disrupted circadian rhythms. Previous research has shown that the body's natural melatonin production declines with age and can also be reduced by excessive exposure to light from screens and other artificial light sources in the evening. Many people take melatonin supplements to improve their sleep, and the new findings suggest that an additional benefit may be enhanced protection of the body's cells against DNA damage.

Since the beginning of human history, our bodies have been designed to be awake during daylight hours and asleep at night. Exposure to daylight stimulates the production of serotonin, a neurotransmitter involved in numerous physiological processes and mood regulation. As darkness falls, serotonin is converted into melatonin, which is the hormone that helps us fall asleep, stay asleep, and wake up feeling refreshed.
Melatonin is also a powerful antioxidant that protects cells and their DNA from oxidative damage caused by free radicals - highly reactive molecules that are produced naturally in the body and are also generated by environmental factors.
However, the body's natural production of melatonin decreases with age. In addition, bright summer nights, exposure to screens and LED lighting in the evening, and certain stimulants can all suppress melatonin production. This may not only impair sleep quality but also increase the risk of oxidative stress, a condition in which harmful free radicals outnumber the body's protective antioxidants.

Testing melatonin supplements in night and shift workers

Night work and rotating shift work can suppress the body's natural production of melatonin, a factor believed to increase the risk of chronic diseases and certain cancers. One of the main reasons is that lower circulating melatonin levels may increase oxidative stress.
The Canadian study therefore investigated whether melatonin deficiency reduces the body's ability to repair oxidative DNA damage, which is associated with an increased risk of cancer and other diseases. The researchers also examined whether melatonin supplementation could improve DNA repair in shift workers.

A marker of DNA repair increased during daytime sleep

The study included 40 healthy adults who had worked rotating night shifts for at least six months. None of the participants had chronic illnesses or diagnosed sleep disorders.
Participants were randomly assigned to one of two comparable groups. One group received 3 mg of melatonin one hour before going to sleep, whether sleeping during the day or at night, while the other group received an identical placebo. The study lasted four weeks.
Urine samples were collected before and during the intervention to measure levels of 8-hydroxy-2'-deoxyguanosine (8-OH-dG), a biomarker associated with the body's repair of oxidative DNA damage. Higher concentrations indicate greater DNA repair activity.
The researchers found that participants who took melatonin before sleeping during the day had 80% higher levels of 8-OH-dG than those receiving placebo. In contrast, no significant difference was observed when shift workers took melatonin before sleeping at night.
Based on these findings, the researchers concluded that melatonin may enhance the ability of shift workers to repair DNA damage. Still, they emphasize that larger clinical studies are needed to determine the optimal dose of melatonin for different individuals and to evaluate its long-term effects on health, including its potential role in preventing cancer and other chronic diseases.
The Canadian study was published in the journal Occupational and Environmental Medicine.

Melatonin during the summer months and as an anti-aging therapy

At northern latitudes, many people may also benefit from melatonin supplementation during the bright summer months, when shorter periods of darkness can reduce the body's natural production of melatonin.
In the following article, you can learn more about how melatonin, through its powerful antioxidant properties, may also contribute to healthy aging.

• Melatonin as an anti-aging therapy against cardiovascular diseases and neurological disorders

References:

BMJ Group. Repairing DNA damage: Scientist discover a surprising new benefit of melatonin. ScienceDaily. 2026

Umaimah Zanif et al. Melatonin supplementation and Oxidative DNA repair capacity among night shift workers: a randomized placebo-controlled trial. Occupational and Environmental Medicine. 2025