The research: Researchers in Montreal and Madrid teamed up to test their hypothesis by giving half of a group of rats a melatonin supplement for 10 weeks, while the other half were given none. Sure enough, at the end of the study period, the melatonin-treated rats had higher bone volume and bone mass than the others. The bottom line: This is the first study demonstrating melatonin’s ability to reclaim bone mass, though the effect has yet to be tested in humans. Until it’s shown to work as a bone builder in humans, it’s still safe to take 40 mg of melatonin every evening to help induce sleep, says study author Jesus A.F. Tresguerres, MD, PhD, a professor in the School of Medicine at Madrid’s Complutense University. You’ll also get immune-boosting and anti-inflammatory benefits, as well as a dose of antioxidants, he says.  More from Prevention: 12 Ways To Break-Proof Your Bones