A small clinical trial reveals that melatonin supplements may help night shift workers repair cellular damage that accumulates from working overnight, offering a potential strategy to counter one of the hidden biological costs of graveyard schedules.
The study, published in Occupational & Environmental Medicine, followed 40 night shift workers over four weeks. Half received a 3 mg melatonin pill daily about an hour before daytime sleep, while the other half took a placebo on the same schedule. All participants had worked at least two consecutive night shifts per week for at least six months.
Researchers measured urinary levels of 8-OHdG, a biomarker that indicates oxidative DNA damage repair capacity. Among workers taking melatonin, this marker was 80% higher during daytime sleep compared to those on placebo. The difference, however, disappeared during the subsequent night shift work period.
The findings target a specific biological vulnerability. Night shift work suppresses normal melatonin production, the hormone that rises with darkness to signal sleep. That suppression may weaken the body's ability to repair oxidative DNA damage, the cellular wear and tear that accumulates through normal metabolism. Reduced repair capacity has emerged as one pathway linking long-term night work to elevated cancer risk.
"Increased oxidative DNA damage due to diminished DNA repair capacity is a compelling mechanism that may contribute to the carcinogenicity of night shift work," the researchers wrote in their conclusion. "Our randomized placebo-controlled trial suggested melatonin supplementation may improve oxidative DNA damage repair capacity among night shift workers."
The trial offers evidence that melatonin may help restore lost repair signals when the body's normal sleep-wake cycle has been inverted. Still, the study was small and short, measuring only a biomarker rather than actual cancer outcomes. Most participants worked in healthcare, limiting how broadly the results may apply. Researchers also could not control for natural light exposure, which independently affects melatonin levels in the body.
The International Agency for Research on Cancer has classified night shift work as probably carcinogenic to humans, reflecting broader scientific concern about long-term effects on health. Beyond DNA repair, persistent overnight work disrupts circadian rhythm, alters hormone signaling, impairs immune function, and triggers metabolic changes.
Scientists stress that larger studies using different doses and longer follow-up periods are needed before melatonin can be recommended as a long-term cancer prevention strategy. The researchers emphasized that anyone working night shifts for years would need consistent supplementation over that time frame to maximize potential benefits.
The results do not prove melatonin prevents cancer. Instead, they strengthen the case for further investigation into whether restoring melatonin signaling could reduce some of the biological strain imposed by working through the night.
Author Jessica Williams: "A promising lead, but this is preliminary evidence that demands much larger, longer studies before night shift workers should expect melatonin to be a cancer prevention solution."
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