Melatonin supplements may make old bones stronger, according to a recent study.

Researchers at McGill University in Canada and the University of Madrid in Spain found that melatonin supplements make bones stronger in elderly rats and therefore, potentially, in elderly humans too. This discovery could lead to the prevention of osteoporosis.

"Old rats are tedious to work with because they get sick a lot and that means they also cost a lot more," Faleh Tamimi, leader of the research team and a professor at McGill's School of Dentistry, said in a statement. "But if you're interested in diseases like osteoporosis, they're an essential part of the process."

For the study, researchers gave twenty 22-month-old rates (the equivalent of 60 year-old humans) melatonin supplements diluted in water for 10 weeks (the equivalent of six years in human years). The femurs taken from the elderly rats which had received the melatonin supplements were then compared with rats in the control group who had not received the supplements using a series of tests to measure bone density and strength.

The researchers found that there was a significant increase in both bone volume and density among the rats that had received melatonin supplements. It took much more force to break the bones of rats that had taken the melatonin supplements, a finding that suggests to the researchers that melatonin may prove a useful tool in combating osteoporosis.

By giving old rats melatonin supplements to regulate their circadian rhythms, the McGill researchers have been able to make their bones denser, less brittle and more flexible. 

Researchers will now look into whether melatonin is preventing or actually reversing the process of bone breakdown.

"Until there is more research as well as clinical trials to determine how exactly the melatonin is working, we can't recommend that people with osteoporosis go ahead and simply take melatonin supplements," Tamimi said. "I am applying for funding to pursue the research and we hope to have answers soon."