On 11 Dec 2006 07:26:33 -0800, "James Semmel"
feetback@shoebusters.com> wrote:
Vitamin D has been getting a lot of media attention in recent years as
being beneficial for several cancers except for one... melanoma. Is it
possible that we're overlooking something?
In general, the exposure to the sunlight's UVB-radiation is slightly
positively associated with melanoma risk. However, the active form of
vitamin D has been shown to inhibit growth of many malignant melanoma
cell lines in the laboratory:
Seifert M, Rech M, Meineke V, Tilgen W, Reichrath J.
Differential biological effects of 1,25-dihydroxyVitamin D3 on
melanoma cell lines in vitro.
J Steroid Biochem Mol Biol. 2004 May;89-90(1-5):375-9.
PMID: 15225804 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=15225804
Even if the sunlight increases melanoma risks slightly, it may reduce
the risk of many other cancers so that if you do your math, you are
better off with getting regularly brief sunlight exposures on the
large enough skin area. The important thing is to avoid sunburns. You
only need 20 minutes of exposure to get the maximum daily amount of
vitamin D, so there is no point in exceeding 20 minutes. After that
you can put on protective clothing and/or apply suncscreen. Some
orally taken natural antioxidants and COX-2 inhibitors may also be
useful.
The worst type of exposure is probably intemittent exposure, when you
get sunlight exposure irregularly and perhaps too long time on each
exposure. That way you may not get enough vitamin D in the long run,
but you may burn your skin. The regular exposure, for example
occupational exposure, is probably better, especially, if you can
avoid longer than 20 minute exposures and sunburns. According to some
studies this kind of exposure may even reduce melanoma risk.
Of course, if you want to avoid sun, vitamin D can always be taken as
a supplement.
Below some references related to the above text:
Ness AR, Frankel SJ, Gunnell DJ, Smith GD.
Are we really dying for a tan?
BMJ. 1999 Jul 10;319(7202):114-6.
PMID: 10398641 [PubMed - indexed for MEDLINE]
http://www.bmj.com/cgi/content/full/319/7202/114
"The main rationale for the health message - reduce exposure to
sunlight, and, in particular, avoid sunburn - has been the belief
that exposure contributes to the increasing incidence of malignant
melanoma.2 However, the exact nature of the association between
malignant melanoma and exposure to sunlight has yet to be
determined.7 A recent systematic review of case-control studies
confirmed that intermittent sun exposure (odds ratio 1.71; 95%
confidence interval 1.54 to 1.90) and sunburn at all ages (1.91;
1.69 to 2.17) were associated with an increased risk of melanoma.
It also showed, however, that people exposed to sun through their
work were at a reduced risk (0.86; 0.76 to 0.96).8 Even if
reducing exposure to sunlight reduces the incidence of melanoma,
its effect on overall mortality will be slight, as the number of
deaths postponed will be small. In 1995, the deaths of 697 men and
698 women in England and Wales were attributed to malignant
melanoma.9 Even the most forceful campaign could be expected to
prevent only a few of these deaths. There may also be effective
options for reducing mortality from melanoma that do not require
reducing exposure to sunlight - for example, by increasing
awareness of the diagnosis and access to treatment."
Elwood JM, Jopson J.
Melanoma and sun exposure: an overview of published studies.
Int J Cancer. 1997 Oct 9;73(2):198-203. Review.
PMID: 9335442 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9335442&dopt=Abstract
"To assess the association between the incidence of cutaneous
melanoma; intermittent, occupational and total sun exposure;
and history of sunburn at different ages, we conducted a
systematic review using results of all published case-control
studies which have assessed incident melanoma, sun exposure and
sunburn. Twenty-nine studies contributed data on sun exposure
and 21 on sunburn. Overall, there was a significant positive
association (odds ratio [OR] = 1.71) for intermittent exposure,
a significantly reduced risk for heavy occupational exposure
(OR = 0.86) and a small, marginally significant excess risk for
total exposure (OR = 1.1

. There was a significantly increased
risk with sunburn at all ages or in adult life (OR = 1.91) and
similarly elevated relative risks for sunburn in adolescence
(OR = 1.73) and in childhood (OR = 1.95). There was significant
heterogeneity with all of these estimates except that of all
ages or adult sunburn. These results show the specificity of
the positive association between melanoma risk and intermittent
sun exposure, in contrast to a reduced risk with high levels of
occupational exposure. The association with sunburn also is
likely to reflect intermittent exposure; the results do not
suggest any strong relationship to age at sunburn. These
associations are similar to those reported for basal cell skin
cancer but different from those reported for squamous cell
cancer. The mechanisms by which intermittent exposure increases
risk, while other patterns of exposure do not, remain to be
elucidated."
Garland FC, White MR, Garland CF, Shaw E, Gorham ED.
Occupational sunlight exposure and melanoma in the U.S. Navy.
Arch Environ Health. 1990 Sep-Oct;45(5):261-7.
PMID: 2256710 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=2256710
Boscoe FP, Schymura MJ.
Solar ultraviolet-B exposure and cancer incidence and mortality in the
United States, 1993-2002.
BMC Cancer. 2006 Nov 10;6:264.
PMID: 17096841 [PubMed - in process]
http://www.biomedcentral.com/1471-2407/6/264
Reichrath J.
The challenge resulting from positive and negative effects of
sunlight: how much solar UV exposure is appropriate to balance between
risks of vitamin D deficiency and skin cancer?
Prog Biophys Mol Biol. 2006 Sep;92(1):9-16. Epub 2006 Feb 28. Review.
PMID: 16603232 [PubMed - indexed for MEDLINE]
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=16603232
Scarlett WL.
Ultraviolet radiation: sun exposure, tanning beds, and vitamin D
levels. What you need to know and how to decrease the risk of skin
cancer.
J Am Osteopath Assoc. 2003 Aug;103(

:371-5. Review.
PMID: 12956250 [PubMed - indexed for MEDLINE]
http://www.jaoa.org/cgi/reprint/103/8/371
Osborne JE, Hutchinson PE.
Vitamin D and systemic cancer: is this relevant to malignant melanoma?
Br J Dermatol. 2002 Aug;147(2):197-213. Review.
PMID: 12174089 [PubMed - indexed for MEDLINE]
http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-2133.2002.04960.x
--
Matti Narkia