Sunlight 'can prevent' skin and non-skin cancers

New York, Jan 8 - It's definitely a puzzle to
scientists, but a new study has suggested that the main cause
of skin cancer -- sunlight -- may also help protect against
the deadly disease as well as other malignant tumours.
A team of international researchers has carried out
the study and found moderately increased exposure to sunlight
not only reduces the risk of getting skin cancer but can also
prevent breast, colon and lung cancers.

"Since vitamin D has been shown to play a protective
role in a number of internal cancers and possibly a range of
other diseases, it is important to study the relative risks to
determine whether advice to avoid sun exposure may be causing
more harm than good in some populations," according to lead
researcher Richard Setlow of Brookhaven National Laboratory.
According to the researchers, solar radiation is a
major, if not the main, source of vitamin D in humans. In the
presence of sunlight, the body converts certain precursor

chemicals to active vitamin D.
But, the researchers have cautioned that too much
exposure to sunlight can cause other skin diseases. "As far as
skin cancer goes, we need to be most worried about melanoma, a
serious disease with significant mortality," Setlow was quoted
by the 'ScienceDaily' as saying.
For the study, Setlow and his colleagues in the
United States and Norway used a special model to calculate the
relative production of vitamin D via sunlight on a group of
people depending on how far they live from the Equator.

According to their findings, people residing in
Australia (just below the equator) produce 3.4 times more
Vitamin D as a result of sun exposure than people in Britain,
and 4.8 times more than people in Scandinavia.
"There is a clear north-south gradient in vitamin D
production with people in the northern latitudes producing
significantly less than people nearer the equator," according

to Setlow.
In populations with similar skin types, there is also
a clear increase in the incidence of all forms of skin cancer
from north to south. "This gradient in skin cancer rates
indicates that there is a true north-south gradient in real
sun exposure," he said.
The scientists also found that the incidence rates of
major internal cancers such as colon cancer, lung cancer, and
cancers of the breast and prostate also increased from north
to south.
However, when the scientists examined the survival
rates for these cancers, they found that people from the
southern latitudes were significantly less likely to die from
these internal cancers than people in the north.
"In previous work, we have shown that survival rates
for these cancers improve when the diagnosis coincides with
the season of maximum sun exposure, indicating a positive role
for sun-induced vitamin D in prognosis.
"The current data provide a further indication
of the beneficial role of sun-induced vitamin D for cancer
prognosis," Setlow said.