Proper sleep in the dark is essential for human health.

Human and animal studies show that light at night is a clear cancer risk. Nighttime exposure to artificial light suppresses production of melatonin which typically peaks in the middle of the night. Research shows an association between melatonin suppression and an increased risk of breast cancer for women night shift workers such as nurses.

The Melatonin hormone produced in our brain’s pineal gland circulates in our blood to help regulate our Circadian rhythms. These are the cyclical periods controlling when we are awake or asleep.

A study published in the Journal of Cancer Research shows when laboratory mice are exposed to artificial light at night, they become stimulated to grow human breast tumors as their melatonin levels are suppressed. The study showed that extended periods of darkness at night would slow the growth of these tumors.

The results seem to explain why female night shift workers have a higher rate of breast cancer. The epidemic rise of breast cancer in industrialized countries may now have a positive solution.

The presence and the absence of light are essential for health.

Consider the lack of Vitamin D and the incidence of Osteomalacia commonly known as Rickets. This was a common disease of 18th century inner city children due to a lack of exposure to sunlight. Excessive air pollution reduced the presence of the ultra-violet portion of sunlight. Vitamin D was found not to be a true vitamin but a hormone produced primarily through a photosynthetic reaction of sunlight in the human body.

Reports indicate an increase of Osteomalacia in nothern China. It may be important to determine if a cause has been due to increased air pollution.
The National Cancer Institute and the National Institute of Environmental Health Sciences, agencies of the US Federal National Institutes of Health, funded research at the Bassett Research Institute of the Mary Imogene Bassett Hospital in Cooperstown, New York, and at The Thomas Jefferson University in Philadelphia. Results were published in the December 1, 2005 issue of the scientific journal Cancer Research.

References:

1. Bright Lights, Big Cancer. Melatonin-depleted blood spurs tumor growth
Publisher: Science News Online Jan 7 2006 Vol 169, No.1 p.8
http://www.sciencenews.org/articles/20060107/bob9.asp

2. Artificial Light at Night Stimulates Breast Cancer Growth in Laboratory Mice
Press Release: 19 December 2005 NIEHS PR #05-22 Publisher: National Institute of Environmental Health Sciences. http://www.niehs.nih.gov/oc/news/cancerlight.htm

3. Melatonin-Depleted Blood from Premenopausal Women Exposed to Light at Night Stimulates Growth of Human Breast Cancer Xenografts in Nude Rats
Authors: David E. Blask1, George C. Brainard2, Robert T. Dauchy1, John P. Hanifin2, Leslie K. Davidson1, Jean A. Krause1, Leonard A. Sauer1, Moises A. Rivera-Bermudez3, Margarita L. Dubocovich3, Samar A. Jasser2, Darin T. Lynch1, Mark D. Rollag4 and Frederick Zalatan
1 Laboratory of Chrono-Neuroendocrine Oncology, Bassett Research Institute, the Mary Imogene Bassett Hospital, Cooperstown, New York; 2 Department of Neurology, Thomas Jefferson University, Philadelphia, Pennsylvania; 3 Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois; 4 Department of Anatomy, Physiology, and Genetics, Uniformed Services University of the Health Sciences, Bethesda, Maryland

Publisher: Cancer Research 65, 11174-11184, December 1, 2005 Volume 65 Issue 23
http://cancerres.aacrjournals.org/cgi/content/abstract/65/23/11174

4. Light at Night and Cancer Risk
Authors: Eva Schernhammer, Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital, and Harvard Medical School, Boston, MA and
Kalr Schulmeister, Austrian Research Centers Seibersdorf, A-2444 Seibersdorf Austria
Publisher: Proceedings of the 25th Session of the CIE. CIE 152:2003 ISBN 3901 90621 5
http://www.cie.co.at/framepublications.html

4. The Biological Potency Of Light In Humans: Significance To Health And Behavior
Authors: George C. Brainard and Gena Glickman
Thomas Jefferson University, Department of Neurology, Philadelphia, Pennsylvania
Publisher: Proceedings of the 25th Session of the CIE. CIE 152:2003 ISBN 3901 90621 5
http://www.cie.co.at/framepublications.html

5. Ocular Input for Human Melatonin Regulation
http://www.uni-koeln.de/symposium2002/brainard.pdf
Authors: George C. Brainard, Department of Neurology, Thomas Jefferson University, Philadelphia, PA, USA; and Robert Levin, Osram Sylvania, Salem, MA, USA 2001

6. Rotating Night Shifts and Risk of Breast Cancer in Women Participating in the Nurses, Health Study Authors: E S Schernhammer, F Laden, F E Speizer, W C Willett, D J Hunter, I Kawachi & G Colditz Publisher: Journal of the National Cancer Institute. 93, pp. 1563-1568, 2001 http://jncicancerspectrum.oxfordjournals.org/cgi/content/abstract/jnci;93/20/1563?fulltext=&searchid=QID_NOT_SET

http://jncicancerspectrum.oxfordjournals.org/cgi/content/full/jnci;94/7/532

Melatonin: http://en.wikipedia.org/wiki/Melatonin

Circadian Rhythm: http://en.wikipedia.org/wiki/Circadian

Rickets: http://en.wikipedia.org/wiki/Rickets

Unraveling the Enigma of Vitamin D: http://www.beyonddiscovery.org/content/view.txt.asp?a=414