As we age, our bones become fragile and more susceptible to painful breaks. But what if we could turn back time and make them tough again? Researchers have discovered that melatonin supplements make elderly rats’ bones stronger, the Toronto Sun reports. After giving 22-month-old rodents—which are the equivalent of 60-year-old humans—the hormone for 10 weeks, scientists saw an increase in bone volume, density, and flexibility. The finding, which is described in Rejuvenation Research, suggests that the supplement could combat osteoporosis.