Keeping the lights on all night might keep away the monsters under the bed, but it also keeps away the “hormone of darkness,” melatonin, according to a new study in the Journal of Clinical Endocrinology and Metabolism. Melatonin, which is secreted into the blood by the brain’s pineal gland at night, is involved in the circadian rhythm. Scientists believe that disrupting circadian rhythms can contribute to metabolic disease. Specifically, melatonin receptor genes have been linked to type 2 diabetes. Melatonin is also a powerful antioxidant that may help prevent cancer.
You don’t want to mess with Mother Nature when it comes to your melatonin production, and that’s exactly what you’re doing if you are up all night with the lights on, according to the study. Exposure to bright room light during the usual hours of sleep suppressed melatonin by more than 50 percent. The study found that even exposure to bright room light in the hours before bedtime shortened melatonin production by about 90 minutes, compared to exposure to dim light during that time.
In their report, the authors concluded that “chronically exposing oneself to electrical lighting in the late evening disrupts melatonin signaling and could therefore potentially impact sleep, thermoregulation, blood pressure, and glucose homeostasis.” It seems that we were not built to have bright light after dusk, when melatonin production is supposed to be gearing up.