Researchers demonstrated that low melatonin levels1 are a risk factor for invasive breast cancer in postmenopausal women. They had already demonstrated the same finding in premenopausal women. Melatonin is the hormone made in your pineal gland that not only helps you sleep but also helps synchronize timing in your body, including the rhythmic function of immune cells. This data indicates that any woman who is 50 or older should ensure her melatonin status is optimal. Taking melatonin and noticing that it helps you sleep better is one sign of need.