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From the Cover: Addressing the health benefits and risks, involving vitamin D or skin cancer, of increased sun exposure.
by Moan J, Porojnicu AC, Dahlback A, Setlow RBProceedings of the National Academy of Sciences of the United States of America.
Article Abstract:
Solar radiation is the main cause of skin cancers. However, it also is a main source of vitamin D for humans. Because the optimal status of vitamin D protects against internal cancers and a number of other diseases, a controversy exists: Will increased sun exposure lead to net health benefits or risks? We calculated the relative yield of vitamin D photosynthesis as a function of latitude with a radiative transfer model and cylinder geometry for the human skin surface. The annual yield of vitamin D is 3.4 and 4.8 times larger below the equator than in the U.K. and Scandinavia, respectively. In populations with similar skin types, there are clear latitude gradients of all major forms of skin cancer, indicating a north-south gradient in real sun exposure. Surprisingly, the incidence rates of major internal cancers also increase from north to south. However, the survival prognosis also improves significantly from north to south. Reasons for these findings are discussed in view of the role of vitamin D. In Norway, melanoma rates increased by a factor of 6 from 1960 to 1990, while the prognosis improved in the same period. After 1990, melanoma rates have remained constant or even decreased in age groups <50 years, whereas the prognosis has not improved further. These data, together with those for internal cancers and the beneficial effects of an optimal vitamin D status, indicate that increased sun exposure may lead to improved cancer prognosis and, possibly, give more positive than adverse health effects.
More sun is healthy, despite skin cancer risk, study says
By: Anonymous - Thu 1/17/2008 PMThis is an eye catching headline, and thought provoking paper - but both are somewhat misleading. In this paper, Johan Moan and colleagues have suggested a slight relationship between the prognosis of some cancers and latitude. That is to say, for some times of cancer, you might be expected to live a little longer if you reside closer to the equator.
The researchers take this discovery and run with ideas and possible explanations. They suggest that patients closer to the equator get more sun, and the sun is responsible for making Vitamin D in the skin. They further suggest that low levels of Vitamin D may put you at risk for not doing as well with some types of cancer.
What is notable here are several things that the researchers have not demonstrated. For example, the researchers have not shown that there is a difference in the level of Vitamin D at different latitudes. Certainly one would expect that if exposed to more sunlight, an individual will produce more Vitamin D. However, Vitamin D also is introduced into our body by the things we eat. Vitamin D is readily supplemented in milk, yogurt, margarine, oil spreads, breakfast cereal, pastries, and bread. It is naturally found in fish, fish oils, mushrooms, and eggs. Several previous studies have looked at Vitamin D levels in different countries, and it is not generally believed by scientists that there is any difference in Vitamin D levels at different latitudes.
Of note, the researchers also present data in their paper that suggests that there is a higher likelihood of developing colon, lung, prostate, and of course melanoma in patients living closer to the equator. This finding was not made much mention of in either the original article, nor the newspaper coverage.
In summary, Vitamin D is an interesting compound that we need to learn more about… but this paper falls far short of the headline it was given “More sun is healthy.†For now, we suggest you stick to your sunblock and hats!
Source: http://belaray.com/blog/?p=78