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Re: Sunshine hormesis - 'Ecological' Study!? :-)
RADSAFERS:
The generation of vitamin D in the skin is the main known benefit of
exposure to ultraviolet radition (UVR). See, for example, item 15 in the
Executive Summary of a substantial NRPB report:
http://www.nrpb.org/publications/documents_of_nrpb/abstracts/absd13-1.htm
In the main body of this report, the NRPB notes that a few minutes of
daily outdoor exposure to the face, hands and forearms are sufficient to
produce all the vitamin D we need. However, it has also been
acknowledged that people living in the northern latitudes may not get an
adequate outdoor exposure in this fashion during the cold winter
months.
I believe that Dr. Hollick receives some funding from the US tanning
industry for his research work. Also, the industry does like to suggest
that indoor tanning is a viable alternative to natural, outdoor tanning
and can be done year round.
It is tempting, therefore, to (try to) suggest that regular visits to a
local indoor tanning salon offers more than just a cosmetic tan.
The problem, though, is that people disrobe completely in an indoor
facility and expose their whole skin surface, including portions that
are niot normally exposed to sunlight. It would be rather silly to have
only one's face, hands and forearms exposed while lying in a tanning bed
- and paying for it to boot!
This sort of reasoning may have been the stimulus for "full spectrum"
indoor lighting (i.e., the bulbs would also produce some UVR to mimic
the sun's spectrum). I don't think this idea has got very far, though.
I would like to know if anyone has further information about it.
Eric Cowdrey, M.Sc. (Physics)
Radiation Protection Officer
Department of Medical Physics
CancerCare Manitoba
675 McDermot Avenue
Winnipeg, Manitoba R3E 0V9
Canada
Tel (204) 787-2166
Fax (204) 775-1684
mailto:Eric.Cowdrey@cancercare.mb.ca
Industrial hygiene in Manitoba: http://aiha.cancercare.mb.ca
Radiology in Manitoba:
http://www.umanitoba.ca/faculties/medicine/radiology
Disclaimer: My statements/opinions do not necessarily represent those
of CancerCare Manitoba
>>> Muckerheide <muckerheide@attbi.com> 02/16/02 05:33PM >>>
Friends,
Note the following conclusions presented at the AAAS 2002 meeting.
Regards, Jim Muckerheide
=======================
Friday, 15 February, 2002, 20:53 GMT
Sunshine 'prevents cancer'
By BBC News Online's Caroline Ryan
A small amount of sunshine can help reduce the risk of breast, colon
and
prostate cancers, according to US scientists.
Sunlight is a key source of vitamin D, and scientists told the
American
Association for the Advancement of Science annual meeting in Boston
the
vitamin plays a crucial role in regulating the production of cells, a
mechanism which is absent in cancer.
The suggestion that we should get out in the sun may at first seem at
odds
with the advice on guarding against the risk of skin, but Professor
Michael
Holick, an endocrinologist from the Boston University School of
Medicine,
stressed that he was advocating moderation, and not denying the
harmful
effects of sunburn.
To get the vitamin D from the sun, but protect against skin cancer, he
suggests Caucasians spend five to 10 minutes in the sun, unprotected,
two to
three times a week. Sun creams should then be used if people spend any
further time in the sun.
Key chemical
People with darker skins need to spend longer in the sun to get the
necessary amount of vitamin D; the pigmentation in their skins blocks
UV
absorption.
The sun gives out ultraviolet (UV) radiation. The benefits come from
the UV
B type.
Professor Holick believes his research could explain why people living
in
colder, northern climates who get less vitamin D from the sun have a
higher
risk of dying from colon, breast and prostate cancers.
He said more people than might be expected were vitamin D deficient.
In
Boston, he estimated 40 to 50% of adults over 50 were vitamin D
deficient.
Professor Holick's team has isolated a key enzyme, or body chemical,
which
is involved in the processing of vitamin D. It was found in the colon.
He
said if the body did not take in enough vitamin D then the enzyme would
not
be activated and the body would not be able to turn the vitamin into a
form
it could use.
The active form of vitamin D prevents colon cells from proliferating
and
prompts them to change into more mature cells which are less capable
of
becoming cancerous.
North and South
The Boston researchers have found the same process occurs in breast,
skin
and prostate cells.
Professor Holick said: "The most beneficial effect of exposure to
sunlight
is vitamin D protection. Moderation is really the answer. We were born
and
evolved in sunlight and so sunlight is probably important for good
health."
Dr William Grant, an independent researcher from Virginia, has examined
the
difference in cancer rates dependent on where people live.
Dr Grant's US work, using data from the Atlas of Cancer Mortality,
found
death rates for breast, colon and ovarian cancers in Boston and New
England
were almost twice as high as they were in the southwest from 1950 to
1994.
He found the same link, with varying increased risk, for 13 cancers
including bladder, kidney, stomach and non-Hodgkin's lymphoma.
He estimates there have been 23,000 deaths from cancer per year -
taking the
difference in UV radiation between northern and southern states -
which
could have been prevented if people had had enough vitamin D. He
suggests
this year, the figure could be 30,000.
Based on his US findings, he estimates a quarter of breast cancer
deaths in
the UK are as a result of vitamin D deficiency.
He told BBC News Online: "I believe my research should be considered a
clarion call for more investigation by the health establishment on the
benefits of solar radiation and UVB."
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