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Did you know that breast Cancer rates in the industrialized world are five times higher than in developing nations?

And there are many theories explaining why. One suggested that artificial lighting at night can increase a woman's risk of breast cancer. This sounded outrageous at the time, yet it is now getting serious re-consideration.

Researchers have a renewed interest because multiple epidemiological studies show women working night shifts experience a sixty percent higher chance of getting breast cancer.

What they've found is a connection to the hormone melatonin. Melatonin is produced in the brain by the pineal gland and its purpose is to regulate our sleep - wake cycle.

Melatonin levels rise in the evening when it's getting dark and prepares our bodies for sleep. As morning approaches melatonin levels fall and we start to wake up.

For night shift workers this cycle is disrupted because artificial lighting entering the eye signals the brain not to make melatonin. How does this raise the risk of breast cancer? It has to do with the interplay between melatonin and a nutrient called linoleic acid. It's a fatty acid found in foods like fish oils. We need it for healthy hair and proper wound healing.

The downside is linoleic acid also enters cancer cells and promotes their growth. Here's where melatonin comes into play. Researchers recently found in lab studies that at night when melatonin is highest, it stops linoleic acid from entering tumor cells and therefore slows their growth.

But night shift workers exposed to bright light at night would not produce melatonin and their tumor cells would continue to grow and spread.

The connection is fascinating but we need more studies. Nonetheless it brings us closer to identifying a cause of breast cancer which is expected to kill forty thousand women in the U.S. this year.

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For more information…

Artificial Light At Night Stimulates Breast Cancer Growth In Laboratory Mice
Article from "ScienceDaily" (Dec. 20, 2005) - "Results from a new study in laboratory mice show that nighttime exposure to artificial light stimulated the growth of human breast tumors by suppressing the levels of a key hormone called melatonin."
For more information…

Light May Be Connected to Breast Cancer
Audio file from National Public Radio about exposure to light at night increasing incidence of breast cancer
For more information…

Bright Lights, Big Cancer: Melatonin depleted blood spurs tumor growth
From Science News online - Description of research that identified light suppression of melatonin as a key element in induction of breast cancer.
For more information…

 
 

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