Melatonin is a natural substance. The pineal gland, located in the brain, makes it and releases it, primariliy at night. Adequate melatonin levels help establish healthy sleep patterns. Malatonin levels decrease as you get older.
Night Shift work ~ Cancer link
On the epidemiological side, “there’s human data — nurses, airplane flight attendants, different groups that engage in shift work — that have an elevated risk of breast cancer, and that’s the strongest finding,” Blair said. “There’s lesser evidence, but some positive evidence, for [increased risk of] prostate cancer, and a little less, but still positive, evidence, for colon cancer.” In animal studies, rats exposed to light during their nocturnal, active phase, also displayed spikes in cancer incidence, Blair said.
In investigations into possible biological mechanisms linking working through the wee hours to heightened odds for malignancy, the strongest theory involves melatonin, a hormone produced by the brain’s pineal gland. Shift workers interrupt their natural melatonin formation. 2007
Researchers in Hong Kong report that the hormone melatonin, more commonly used to reduce the effects of jetlag, could protect the brain from the effects of stroke. March, 2003