Washington, Jan 8 : A new study by researchers at the U.S. Department of Energy's Brookhaven National Laboratory and colleagues in Norway has cited that sun exposure may boost up Vitamin-D production and thereby reduces the risk of skin cancer and other diseases in certain vitamin D lacking populations. However, it is well known that solar radiations such as ultraviolet A (UVA) radiations can lead to many types of skin cancer, but they are also a major source of vitamin D in humans as many of the body's precursor chemicals get converted into active vitamin-D in the presence of sunlight.
The study was led by Richard Setlow, a Senior Biophysicist Emeritus at Brookhaven and a well-known expert on the link between solar radiation and skin cancer, who said that it was important for them to know if "advice to avoid sun exposure may be causing more harm than good in some populations".
He also said that the concern for such an effect is greater in populations from northern latitudes, such as Scandinavia, where sun exposure is extremely limited.
In the current study, the researchers used a model containing information on solar radiation intensity and a vertical cylinder shape to represent the human body's skin surface in order to calculate the relative production of vitamin D via sunlight as a function of latitude, or distance from the equator.
The cylindrical model represented human body sun exposure much more realistically than flat surface exposure measurements used in previous models. The incidence of and survival rates for various forms of cancer by latitude was also observed.
The calculations revealed that people residing in Australia (just below the equator) produce 3.4 times more vitamin D as a result of sun exposure than people in the United Kingdom, 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," said Setlow.
Also, a clear increase in the incidence of all forms of skin cancer from north to south was seen in populations with similar skin types.
"This gradient in skin cancer rates indicates that there is a true north-south gradient in real sun exposure," Setlow says.
It was 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 survival rates for these cancers were examined, it was discovered that people from the southern latitudes were considerably less prone to die from these internal cancers than people in the north.
The study is published online in the Proceedings of the National Academy of Sciences.