Health Benefits of Ultraviolet Radiation
By William B. Grant, Ph.D.
Founding Director,
Sunlight, Nutrition and Health Research Center (SUNARC)
www.sunarc.org
wgrant@sunarc.org
Re: EPA and NOAA’s New Global Ultraviolet Index Guidelines (Guidance helps reduce
overexposure to dangerous UV rays)
http://yosemite.epa.gov/opa/admpress.nsf/b1ab9f485b098972852562e7004dc686/e7cb2e
2d5d3231aa85256ea0004f3fdc
While it is important to find ways to reduce the risk of skin cancer and melanoma, and
the UV Index may aid in that effort, I wonder whether those of you working on this effort
have considered the health benefits of UV radiation (UVR).
Item – human skin pigmentation has adapted over periods of millennia to the local UV
levels in order to permit people to produce vitamin D from UVB while protecting the
skin from free radicals and DNA damage from UVR [Jablonski and Chaplin, 2000]. Of
course, most European Americans have skin pigmentation adapted to UVR at about 50
deg. N, so have skin that is not ideally suited for the U.S. (latitudes 26–47 deg. N). On
the other hand, most Americans do not spend the same amount of time in the sun as did
our ancestors, and many who live in the southern states have darker skin due to African
or Hispanic heritage.
Item – Most Americans obtain most of their vitamin D from solar UVB radiation [Holick,
1987]. Dietary sources of vitamin D are insufficient to reduce the risk of cancer in a
significant manner, but supplements and UVB can [Grant and Garland, in press].
Item – the UV Index Contour Map for May 26, 2004, as well as the DNA-weighted UVB
map for July 1992 [Herman et al., 1999] are inversely correlated with the maps of 16
types of cancer in the Atlas of Cancer Mortality [Devesa et al., 1999; Grant, 2002]. My
current estimate is that 47,000 Americans die prematurely annually from 16 types of
internal cancers, in part due to their geographic location, in part due to living in urban
areas where they receive less UVR due to staying indoors more [Grant, submitted].
Item – multiple sclerosis (MS) prevalence in the U.S. increases rapidly with latitude
[Kurtzke et al., 1979; Wallin et al., 2004]. The risk of MS is strongly linked to vitamin D
deficiency [Hayes, 2000; Embry, 2004]. The symptoms of MS can be reduced by UVB
and vitamin D [Embry et al., 2000]. And, perhaps most surprising to this group, those
with skin cancer in the U.K. were found to have half the rate of MS of the general
population [Goldacre et al., 2004]. I estimate that half of the 400,000 with MS in the
U.S. would not have MS if they had the same UVB doses as those living in the southern
states.
Item – occupational exposure to UVR reduces the risk of melanoma [Kennedy et al.,
2003]. More important risk factors include fair skin, sunburning, a high fat, low fruit and
vegetable diet, and, perhaps, smoking.
Item – no study has been able to link increased risk of melanoma to indoor tanning in the
U.S. There have been only two studies investigating the link between melanoma and
indoor tanning facilities in the U.S. The one in the San Francisco Bay Area [Holly et al.,
1995], found an insignificant reduced risk of melanoma among women who used tanning
facilities. The one in Connecticut [Chen et al., 1998] found an insignificant increase.
While use of indoor tanning facilities in Canada and Europe is associated with a 50%
increase in melanoma rates [Young, 2004], it may well be that use of tanning facilities is
better regulated and controlled in the U.S. than in Canada and Europe.
As for other skin cancer associated with indoor tanning facilities, a recent paper tried to
make the case that they were associated with increases in squamous cell carcinoma
(SCC) in Sweden, basing the claim on increases of SCC on parts of the body not
normally exposed to sunlight [Hemminki et al., 2003]. However, the rates increased at
twice the rate for males than for females, in agreement with relative rates of smoking
between the sexes, not with respect to frequency of tanning, which is twice as high for
females than for males in Sweden and the U.S. [Grant, 2004].
Item – vitamin D has many other health benefits than discussed here. The interested
reader is referred to such papers as those by Holick [2003, 2004], Grant and de Gruijl
[2003], Hayes et al. [2003], Heaney [2003], Plotnikoff et al. [2003], Stokstad [2003],
Grant et al. [2004].
So, what do I suggest? How about a balanced presentation regarding the health risks of
excess UVR exposure and the health benefits of moderate UVB exposure? See, e.g.,
Fuller [2003] and, of course, our web site, www.sunarc.org. Note that the UV Index
could also be the basis for determining how long one should stay in the noonday sun to
produce the proper amount of vitamin D.
I would be interested in your comments and a dialogue on this important issue.
Best regards,
References (abstracts may be viewed at www.ncbi.nlm.nih.gov/pubmed)
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Devesa SS, Grauman DJ, Blot WJ, Pennello GA, Hoover RN, Fraumeni JF Jr. Atlas of
Cancer Mortality in the United States, 1950-1994. NIH Publication No. 99-4564, 1999.
http://cancer.gov/atlasplus/new.html (accessed May 21, 2004)
Embry AF. Vitamin D supplementation in the fight against multiple sclerosis. J
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