Melatonin supplements may boost DNA repair in night shift workers, study suggests
A new pilot study suggesting that melatonin supplements may help night shift workers boost their body's DNA repair processes was reported by Science Daily. The findings are early but raise the possibility of a simple strategy to reduce long-term health risks — such as cancer — that are linked to disruption of the circadian rhythm.
The study was carried out by a research group at Mount Sinai Hospital in Toronto, with support from the Public Health Agency of Canada. Eighty male and female hospital workers participated; all routinely worked night shifts. Participants were randomly divided into two groups: one received 3 milligrams of melatonin per day, the other received a placebo (a fake medication).
Over the four-month study, urine samples were collected weekly from participants and tested for a biomarker of DNA damage known as 8-hydroxy-2′-deoxyguanosine (8-OHdG). This biomarker reflects oxidative-stress-related DNA damage and the body's processes for repairing such damage. In night shift workers, melatonin's natural release is reduced during dark periods and the biomarker is typically elevated.
The study's main finding was that 8-OHdG levels in the urine of the melatonin-supplemented group were approximately 28 percent lower than in the placebo group. This suggests that the melatonin supplement does not provide protection against DNA damage itself, but rather supports the body's process of repairing such damage. Dr Parveen Bhatti, the senior researcher on the study, said 'the importance of the results is not that night work increases DNA damage; it is that night work blocks the repair of that damage'.
The long-term health effects of night shift work have been studied for some time. The World Health Organization's International Agency for Research on Cancer (IARC) classified night shift work as 'possibly carcinogenic' (category 2A) in 2007. The link between night shift work and breast cancer in particular is the most well-documented association in the epidemiological literature. There are roughly 15 million night shift workers in the United States.
Melatonin is a hormone produced by the brain's pineal gland, whose release increases during dark periods. Its natural functions include regulating the sleep-wake cycle and providing antioxidant protection. Night shift workers, because they have to sleep during the day and are exposed to light at night, have their natural melatonin release suppressed. Bhatti's research group wanted to measure how supplementation artificially compensates for this deficit.
The study's strengths include its randomised-controlled design and relatively long duration. Against that, the study size (80 participants) is relatively small and cannot definitively establish causal effects. Dr Aaron Drucker, a University of Toronto epidemiologist, told Science Daily that 'the study methods are solid, but additional research is needed to support large-scale public health recommendations'.
On safety, melatonin supplementation is generally well tolerated. The most common known side effects are mild drowsiness, headache and upset stomach. No serious adverse events were reported in either group of the study. However, the Public Health Agency of Canada noted that the supplementation dose is substantially lower than the over-the-counter 5-10 milligram doses sold in the US — suggesting individuals should not assume similar effects from self-administered higher doses.
Bhatti's group is planning an expanded study of 1,200 participants as the next step; participants will be followed for 18 months, and long-term health indicators (including cancer events) will be monitored. The study is expected to conclude around mid-2027. Before this study concludes, night shift workers are advised to consult their own physicians to develop a personal risk-reduction strategy.
This article is not medical advice. Readers considering melatonin supplementation should speak with their physician and assess their personal health circumstances. In some countries, melatonin is sold by prescription only (for example, in the United Kingdom), and it is not recommended for pregnant or nursing women. Health protection strategies for night shift workers also include reducing light exposure, high-quality daytime sleep and regular eating patterns; supplementation may be a complement to, rather than a replacement for, these strategies.