can adversely affect this normal decline, leading to hypertension and cardiovascular problems. Finally,
insufficient sleep impairs the body's ability to use insulin, leading to the onset of diabetes.
The Dark Side Of Light In The Night—Cancer Growth
As indicated before, one of the most important findings ever discovered with regard to cancer is that
low levels of melatonin in the blood drastically increase the risk of cancer. According to the Nurse’s
Study (reported Jan. 2006), which is the most comprehensive and longest-lasting cancer study in the
world, low blood melatonin in registered nurses was found to be responsible for a 50 times higher risk of
developing cancer. Nurses suffer from disrupted sleep cycles due to the nature of their work. Melatonin
controls the gene responsible for keeping the life cycles of cells in the body in check. In other words, the
less melatonin you make during the night, the more likely it is that cells will live beyond their natural life
cycle and thus become cancerous.
The first indications of the damaging effects of light on melatonin secretions during the night were
observed in rodents. “At least in rats, a little light throughout the night can have a dramatic impact on
cancer,” observes David E. Blask of the Mary Imogene Bassett Research Institute in Cooperstown, N.Y.
By exposing rats to constant light, which causes a near-total suppression of melatonin, Blask showed that
tumors can grow especially rapidly. Even small amounts of light can interfere with the body’s natural
biological rhythms. Blask’s team reported that tumors grew almost twice as fast in animals exposed to just
the crack of light coming under the room’s door as they did in animals getting a night of total darkness.
Blask has performed cancer research for over 30 years and specifically studied melatonin for the last
20 years. The discoveries that melatonin inhibits cancer growth and that light inhibits melatonin
production are monumental with regard to cancer treatment and cancer prevention. According to Blask,
melatonin is a fundamental signal that relays rhythmic information about environmental cycles of light
and darkness to all the cells in the body, including cancer cells.
He discovered that increased dietary intake of linoleic acid (a common polyunsaturated fatty acid)
stimulates cancer growth rates because cancer cells take up and metabolize linoleic acid. During darkness,
high levels of melatonin released by the pineal gland block the ability of tumors to take up linoleic acid
and convert it to 13-HODE (a molecule called 13-hydroxyoctadecadienoic acid). While exposed to light,
however, melatonin levels are extremely low, and tumors are no longer protected by melatonin from the
tumor-stimulating action of linoleic acid. In other words, exposure to artificial light when it is naturally
dark, scrambles the molecular clocks in our brains. Light presented during the night will immediately
turn off melatonin production and thus support tumor growth.
Organizations that contributed to Blask’s research are members of the Basset Research Institute
Laboratory of Chrono-Neuroendocrinology, the Thomas Jefferson University Medical School, the
University of Connecticut School of Medicine, and the Northwestern University School of Medicine.
Funding for the research came from the Stephan C. Clark Foundation, the National Cancer Institute, the
Laura Evans Memorial Breast Cancer Fund of the Edwin W. Pauley Foundation, the National Institute of
Environmental Health Sciences and the Louis Busch-Hager Cancer Center Research Fund. Support from
these organizations indicates somewhat of a shift in policy on cancer research.