Posted on March 8, 2010 - by Venik

Working outdoors reduces men’s risk of kidney cancer, study says

Research shows vitamin D, produced by skin when exposed to ultraviolet light, associated with reduced rate of renal cancer

Men who work outdoors, enabling their bodies to create vitamins through exposure to sunlight, have a reduced risk of kidney cancer, researchers said today.

In the largest study of its kind, scientists found that vitamin D – produced by the skin when exposed to ultraviolet light – was associated with a reduced rate of renal cancer of up to 73% among men.

However, the study, published by the American Cancer Society, found that the reduced risk only applied to men – there was no drop in renal cancer among the women studied who worked outdoors.

The researchers, from the National Cancer Institute in the US, said the study of 2,500 workers in central Europe supported emerging evidence that the prevalence of a number of cancers, including breast, ovarian and colorectal cancer, was lower when people were exposed to ultraviolet light.

They said vitamin D, a known anti-carcinogenic, was carried by the body to the liver and on to the kidneys, and recommended further research.

“Scientific evidence suggests that vitamin D, which is generally made in the body after exposure to the sunlight, may help prevent a number of diseases including cancer,” the research author, Sara Karami, said.

“In our study, we used job titles to estimate sunlight exposure at work. We observed that men with high estimated levels of sunlight exposure had a lower risk of kidney cancer than men who had lower estimated sunlight exposure at work.”

Scientists have monitored an increase in renal cell carcinoma (RCC), the main form of kidney cancer, in the US and globally over the past 20 years.

A reduction in vitamin D – probably caused by many more people having sedentary lifestyles and indoor jobs – is believed to be likely to be a contributory factor.

The researchers studied more than 2,500 workers of Caucasian descent in Russia, Romania, Poland and the Czech Republic, splitting them into three groups according to exposure to daylight in their jobs.

A significant fall of up to 38% in the risk of RCC was found with increasing occupational UV exposure among men.

In northernmost regions, that increased to a 73% drop – but after finding no similar decrease in risk for women, Karami said: “We do not have an explanation for the apparent differences in risk between men and women.”

“Biological or behavioural differences between men and women may play a role. For example, hormonal differences may influence the body’s response to sunlight exposure, and men may be prone to working outdoors while shirtless.”

Although some foods contain vitamin D, the majority of people receive up to 90% of the chemical through exposure to ultraviolet light.

Farm workers and those who receive strong UV light reflected from the sea were in the highest category. Those in high sunlight jobs were assumed to receive double the intensity of sunlight to those in low exposure jobs.

Despite the findings, the researchers warned against ignoring the “well-documented risks” of skin cancer resulting from excess exposure to the sun.

“There are no public health recommendations from this study. Men and women should continue to consult their health care providers regarding the appropriate amount of sun exposure, weighing the well-documented risks between sun exposure and skin cancer risk,” Karami added.

Healthy Caucasians can generate a full dose of vitamin D with 10-20 minutes exposure to strong sunlight on unprotected skin. After that, photo-degradation ensures no higher levels are created.

The anti-carcinogenic properties of vitamin D include the prevention of tumour cell replication.

Original article

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