Melatonin Supplementation Could Improve DNA Repair in Night Shift Workers

Disruption of the natural sleep-wake cycle in night shift workers results in decreased melatonin production, which is a hormone that is essential for DNA repair. The decreased ability to repair oxidative DNA damage could place night shift workers at an increased risk of developing cancer. New study findings published in Occupational & Environmental Medicine assessed the efficacy of melatonin supplementation in enhancing oxidative DNA damage repair among individuals engaged in night shift work.¹

Image credit: vetre | stock.adobe.com

As a natural hormone, melatonin is primarily produced by the pineal gland that is in the brain and part of the endocrine system. The pineal gland releases the highest levels of melatonin when there is darkness and decreases melatonin in the blood when exposed to light. Melatonin is released accordingly when the pineal gland receives information about the day-night cycle from the retinas. This plays a significant role in managing the sleep-wake cycle, as the longer an individual’s sleeps at night, the longer the pineal gland secretes melatonin. Despite being referred to as the “sleep hormone,” melatonin is not generally for sleeping, but better sleep can occur when an individual has the highest levels of melatonin in their body.²

Hypomelatoninemia is one of the main conditions that involve melatonin issues, defined as lower-than-normal peak nighttime melatonin levels or lower-than-normal total production levels of melatonin compared to what is anticipated based on individuals' age and sex. Shift work is identified as a secondary cause of hypomelatoninemia, which can contribute to other health conditions, including hypertension, insulin resistance, obesity, and metabolic syndrome. It also places individuals at an increased risk of breast and prostate cancer as well as type 2 diabetes.²

Melatonin has direct and indirect antioxidant properties, including sifting of reactive oxygen species (ROS), and when produced through cellular metabolism, it can cause DNA damage that contributes to the pathogenies of cancer. The study authors noted that 8-hydroxy-2′-deoxyguanosine (8-OH-dG) is the most commonly occurring DNA lesion induced by ROS. Further, previous studies showed night shift workers have lower levels during work and daytime sleep, correlating with decreased melatonin, suggesting impaired DNA repair.¹

Expanding on research from previous studies, researchers conducted a randomized placebo-controlled trial (NCT03945955) that assessed the use of oral melatonin supplementation among night shift workers in Canada to evaluate its impacts on 8-OH-dG excretion as a measure of oxidative DNA damage repair capacity.¹

A total of 40 night shift workers were included in the study, recruited based on data from previous observational studies. Participants were randomized and blinded to receive either a 3 mg dose of melatonin or a placebo in a 1:1 ratio, taking the supplement before daytime sleep for 4 weeks. Data, including urine and sleep measures, were collected before and after the intervention. Participants followed protocols for urine collection during day sleep and night shift periods, according to study authors.¹

The results demonstrated that melatonin supplementation was associated with a borderline statistically significant 1.8-fold increase in urinary 8-OH-dG excretion during day sleep (95% CI 1.0, 3.2, P = 0.06) compared with placebo. However, there was no statistically significant difference in 8-OH-dG excretion during the subsequent night shift between the melatonin and placebo groups (excretion ratio = 0.9; 95% CI 0.6, 1.5; P = 0.7).¹

Additionally, further results demonstrated that night shift workers that received the 3 mg melatonin supplement had supraphysiologic melatonin levels compared to day shift workers assessed in previous studies, but levels were highly variable. When participants with the lowest melatonin levels were excluded, a statistically significant increase in urinary 8-OH-dG excretion was observed, indicating that differences in melatonin bioavailability make it difficult to regulate an ideal supplement dose.¹

The findings suggest that melatonin supplementation could improve oxidative DNA damage repair capacity among night shift workers. However, the study authors noted that further research is needed to identify the impact of varying doses.¹

REFERENCES

1. Melatonin supplementation and oxidative DNA damage repair capacity among night shift workers: a randomized placebo- controlled trial. Occupational & Environmental Medicine. News release. Published February 24, 2025. Accessed March 6, 2025. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://oem.bmj.com/content/oemed/82/1/1.full.pdf

2. Melatonin. Cleveland Clinic. News release. Updated July 5, 2022. Accessed March 6, 2025. https://my.clevelandclinic.org/health/articles/23411-melatonin