Our sleep/wake cycle is biorhythmic behavior. Our bodies are in tune with bright, solar days and dark nights. Since the industrial revolution, we have become used to dim days and bright nights. The results are sleep disturbances with increased risk for cardiovascular disease, gastrointestinal disease, diabetes and obesity. Functions of melatonin include pituitary hormone release, production of testosterone by the testes, adrenal production of cortisol, vascular tone, energy metabolism, cancer cell growth, etc.
Pineal glands produce melatonin from tryptophan, depending on the light/dark cycles of the day. Exposure of the eye to light during a normally dark time resets the melatonin cycle, reducing production. The amount of melatonin produced under ideal conditions is inherited. Maximum melatonin is produced at puberty with declining levels during old age. Darkness at night is necessary for melatonin production. It is excreted in the urine as 6-sulfatoxymelatonin.
Melatonin is needed for normal immunity. Women who slept 9 hrs or more per night had a 72% reduction in breast cancer risk compared to women who slept 7-8 hrs. Melatonin reduces carcinogen-caused DNA damage. Melatonin is a free radical scavenger. Melatonin prevents proliferation of human cancer cell lines. Melatonin reduces the production of the inflammatory omega-6 fatty acids.
Exposure to bright lights at night blocks the anticancer effect of melatonin. A study in Israel comparing the brightness of communities at night showed a 73% higher incidence of breast cancer in the communities with the brightest lighting at night. Night shift workers have a deficiency of melatonin and an increased risk of developing cancers of the breast, prostate, colon and uterus.
CONCLUSION: Melatonin prevents the DNA damage caused by carcinogens, increases DNA repair and helps prevent the damaging effects of omega-6 fatty acids. Melatonin is a pineal hormone produced in the night under dark conditions. Anticancer effects have been found, especially against breast cancer.
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