Reducing the Risk of Cancer by 50 Percent Appears Possible by Blocking Blue Light in the Evening

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Blind people have half the incidence of cancer, most likely because they make melatonin 9 or 10 hours a night according to a recent study at Harvard University. The body can only make melatonin when in the dark. For most people this is 6 or 7 hours a night. It’s the blue component of light that causes melatonin suppression. Glasses that block blue light worn a few hours before bedtime allow melatonin to flow for 9 or 10 hours.

Blind people have about half the risk of cancer as people with normal vision according to a large study by the National Health Service. The most likely reason is that they produce melatonin and other secretions from the pineal gland for 9 or 10 hours a night while the rest of us only make them for 6 or 7 hours a night. Melatonin is a powerful cancer fighter, but the body only make it when in the dark. Exposing the eyes to light shuts down the pineal gland.

But there is good news. Not all colors of light cause melatonin suppression. It’s only the blue rays that cause the problem. This means that blocking the blue light from entering the eye the pineal gland can continue making melatonin. Glasses that block blue light are available at

The fact that blind people only have half the rate of cancer was first discovered in the 90s and has been confirmed by more recent studies. A related study of women who consistently sleep unusually long found that the incidence of breast cancer for women who slept nine hours or more a night was only about one fourth that of women who slept 6 or 7 hours a night. A subsequent study found that women who slept unusually long made melatonin for a similarly unusually long time.

Concern about the use of light at night began when it was found that nurses who worked night shift from time to time had a higher incidence of breast cancer. Something about disrupting the circadian rhythm of the body was causing a higher risk of cancer. Studies in animals show that continuous exposure to light accelerates the rate of growth of cancerous tumors. The mechanism is thought to be the lack of melatonin.

Last fall the results of a milestone study were published. The response of human breast cancers to blood with and without pineal secretions was studied. Breast cancers grew rapidly when exposed to blood without melatonin but only very slowly when the blood contained melatonin. Dr. Blask who led the study said that "Melatonin puts the cancer to sleep at night". Unfortunately exposing the eyes to light at night wakes up the cancer and lets it grow rapidly.

Wearing glasses that block the blue light for a few hours before going to bed lets people regain the long hours of melatonin flow that is experienced by blind people. The glasses allow the yellow, orange and red light to pass through so one can read, watch television or work on a computer with no problem. Users of the glasses also report a marked improvement in sleep, which supports the idea that more melatonin is being produced. This minor change in life style could cut cancer risk in half.

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Dr. Richard L. Hansler


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