A finding on melatonin and DNA protection
A study from BC Cancer Research Institute and the University of British Columbia (UBC), published in BMJ Occupational & Environmental Medicine, brings new data on melatonin's protective effects in night shift workers. The protocol: night shift workers took 3mg of melatonin before their daytime sleep. Result: an 80% increase in urinary 8-OH-dG — a key biomarker for DNA repair.
What is 8-OH-dG?
8-hydroxy-2'-deoxyguanosine (8-OH-dG) is a marker of oxidative DNA damage and repair. When DNA is damaged by reactive oxygen species (oxidative stress), the body activates repair mechanisms — and 8-OH-dG is one of the repair products. Higher levels of this biomarker indicate more active DNA repair. Night shift work is known to increase oxidative stress through circadian disruption in shift workers. The biological clock regulates not just sleep but also many cellular repair mechanisms that normally activate at night. When that rhythm is inverted, natural protection against oxidative damage degrades.
Why melatonin might help
Melatonin is a potent antioxidant — a property often overlooked behind its role as a sleep regulator. It crosses cell membranes easily and can act directly on free radicals that damage DNA. In night shift workers, whose natural melatonin production is disrupted (they sleep during the day, when light inhibits melatonin secretion from the pineal gland), supplementation could partially compensate for this lost protection. The 80% increase in 8-OH-dG observed in the study suggests melatonin either stimulates DNA repair activity or protects DNA well enough that repair mechanisms have less work to do afterward.
Study limitations
Caution is warranted. This study measures a repair biomarker — not long-term health outcomes like cancer risk. The link between higher 8-OH-dG levels and better long-term health is plausible but not proven by this study alone. Night shift workers are also a specific population — results don't necessarily generalize to everyone who takes melatonin as a sleep aid.
What it means practically
For athletes and people with irregular schedules (frequent travel, shift work, unusual hours), this study adds to the case for targeted melatonin use — not just as a sleep tool, but as a cellular protection strategy. The dose used in the study (3mg) is moderate and within the typical range of available supplements. Those with disrupted schedules may also benefit from reviewing magnesium's role in sleep quality for athletes, where similar questions around supplementation timing and cellular recovery apply.