DNC News

Melatonin benefit confirmed in Breast Cancer

January 10, 2006

Subject: New study on benefit of melatonin in treating breast cancer and a mini book review.

Melatonin is a hormone secreted by the brain at night. Its release is triggered by darkness. Perhaps it is better to say absence of light. Light will suppress or stop melatonin production. The modern world is a world of artificial lighting and as a result people make far less melatonin than they did once upon a time. This decrease in melatonin has been associated with an increase in cancer rates. People who work night shifts have higher cancer rates. People who are blind and who use less indoor lighting, have much lower rates of cancer.

A study published a few weeks ago has added another layer of evidence in support of melatonin's action in inhibiting breast cancer. It just so happened that the day the study came out my daughter encouraged me to start reading a new book by one of her favorite authors, Cornelia Funke. There's a passage that caught my attention and had me thinking about how brightly lit our world is. In the book, Inkspell , the character Dustfinger finds himself transported from our modern world back into the fictional world from which he originally came. He enters a rustic inn at the edge of the forest:

“It was so dark in the room inside that his eyes took a little while to adjust to the dim light. The other world had spoiled him with all its lights, with the brightness that made even night into day there. It had accustomed him to seeing everything clearly, to thinking of light as something you could switch on and off, available whenever you wanted. But now his eyes must cope again with a world of twilight and shadows, of long nights as black as charred wood, and houses from which the sunlight was often shut out, because heat was unwelcome.”

Below is the press release distributed by the National Institute of Health (NIH):

December 19, 2005:
 
NEW RESEARCH SHOWS ARTIFICIAL LIGHT AT NIGHT STIMULATES BREAST CANCER GROWTH IN LABORATORY MICE

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. The study also
showed that extended periods of nighttime darkness greatly slowed the
growth of these tumors.

The study results might explain why female night shift workers have a
higher rate of breast cancer. It also offers a promising new explanation
for the epidemic rise in breast cancer incidence in industrialized
countries like the United States .

The National Cancer Institute and the National Institute of
Environmental Health Sciences, agencies of the federal National
Institutes of Health, provided funding to researchers at the Bassett
Research Institute of the Mary Imogene Bassett Hospital in Cooperstown ,
New York and The Thomas Jefferson University in Philadelphia , Pa. The
results are published in the December 1, 2005 issue of the scientific
journal "Cancer Research".

"This is the first experimental evidence that artificial light plays an
integral role in the growth of human breast cancer," said NIEHS Director
David A. Schwartz, M.D. "This finding will enable scientists to develop
new strategies for evaluating the effects of light and other
environmental factors on cancer growth."

"The risk of developing breast cancer is about five times higher in
industrialized nations than it is in underdeveloped countries," said Les
Reinlib, Ph.D., a program administrator with the NIEHS' grants division.
"These results suggest that the increasing nighttime use of electric
lighting, both at home and in the workplace, may be a significant
factor."

Previous research showed that artificial light suppresses the brain's
production of melatonin, a hormone that helps to regulate a person's
sleeping and waking cycles. The new study shows that melatonin also
plays a key role in the development of cancerous tumors.

"We know that many tumors are largely dependent on a nutrient called
linoleic acid, an essential fatty acid, in order to grow," said David
Blask, M.D., Ph.D., a neuroendocrinologist with the Bassett Research
Institute and lead author on the study. "Melatonin interferes with the
tumor's ability to use linoleic acid as a growth signal, which causes
tumor metabolism and growth activity to shut down."

To test this hypothesis, the researchers injected human breast cancer
cells into laboratory mice. Once these cells developed into cancerous
tumors, the tumors were implanted into female rats where they could
continue to grow and develop.

The researchers then took blood samples from 12 healthy, premenopausal
volunteers. The samples were collected under three different conditions
-- during the daytime, during the nighttime following 2 hours of
complete darkness, and during the nighttime following 90 minutes of
exposure to bright fluorescent light. These blood samples were then
pumped directly through the developing tumors.

"The melatonin-rich blood collected from subjects while in total
darkness severely slowed the growth of the tumors. "These results are
due to a direct effect of the melatonin on the cancer cells," said
Blask. "The melatonin is clearly suppressing tumor development and
growth."

In contrast, tests with the melatonin-depleted blood from light-exposed
subjects stimulated tumor growth. "We observed rapid growth comparable
to that seen with administration of daytime blood samples, when tumor
activity is particularly high," Blask said.

According to the researchers, melatonin exerts a strong influence on the
body's circadian rhythm, an internal biological clock that regulates
sleep -- wake cycle, body temperature, endocrine functions, and a number
of disease processes including heart attack, stroke and asthma.
"Evidence is emerging that disruption of one's circadian clock is
associated with cancer in humans, and that interference with internal
timekeeping can tip the balance in favor of tumor development," said
Blask.

"The effects we are seeing are of greatest concern to people who
routinely stay in a lighted environment during times when they would
prefer to be sleeping," said Mark Rollag, Ph.D., a visiting research
scientist at the University of Virginia and one of the study co-authors.
"This is because melatonin concentrations are not elevated during a
person's normal waking hours."

"If the link between light exposure and cancer risk can be confirmed, it
could have an immediate impact on the production and use of artificial
lighting in this country," said Richard Stevens, Ph.D., an
epidemiologist with the University of Connecticut Health Center who has
authored several papers on the subject. "This might include lighting
with a wavelength and intensity that does not disrupt melatonin levels
and internal timekeeping."

"Day workers who spend their time indoors would benefit from lighting
that better mimics sunlight," added Stevens. "Companies that employ
shift workers could introduce lighting that allows the workers to see
without disrupting their circadian and melatonin rhythms."

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Back to Inkspell . I haven't finished the book yet. My daughter told me that although she loved the book, she hated how it ended.

Abstact of the current study: