Darkness, melatonin may stall breast and prostate cancers
New studies suggest people need to respect the body’s desire for nighttime darkness
By Janet Raloff
To stay healthy, the body needs its zzz’s. But independent of slumber, human health also appears to require plenty of darkness — especially at night. Or so suggests a pair of new cancer studies.
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One found that among postmenopausal women, the lower the overnight production of melatonin — a brain hormone secreted at night, especially during darkness — the higher the incidence of breast cancer. The second study correlated elevated prostate cancer incidence around the world with places that have the brightest signatures of light in satellite imagery.
Trends seen in both studies bolster animal data indicating that natural nighttime peaks in blood concentrations of melatonin, which tend to occur during sleep, depress the growth of the hormonally sensitive cancers.