Could Sunlight Decrease the Risk of Getting Lung Cancer?

A recent research study, published in the Journal of Epidemiology and Community Health, is showing that the lack of sunlight may increase the risk of lung cancer. The study led by Dr. Garland, from the Department of Family and Preventive Medicine, University of California, LA Jolla, CA, is titled "Could ultraviolet B irradiance and vitamin D be associated with lower incidence rates of lung cancer?"

More than 100 countries (111 specifically) participated in this study that examined the relationship between sunlight exposure and lung cancer. The International Agency for Research on Cancer GLOBOCAN database was used in this study. GLOBOCAN utilizes national cancer registries to calculate annual incidence rates for lung cancer.

Using countries located at different latitudes and hence receiving different amounts of irradiation (sunlight) and their lung cancer incidences they try to establish a relationship between lung cancer risk and sunlight exposure.

As expected the most associated thing with lung cancer was Smoking, which is responsible for 75 to 85% cases of lung cancer, according to the study. However, interestingly enough was the fact that a good correlation was observed between exposure to sunlight, especially UVB light, and lung cancer.

As known, the UVB light increases near the equator. This is because sunlight hits directly in an almost perpendicularly. Lung cancer database analysis showed that that the prevalence of this disease was lower in the countries near the equator while, on the contrary, as you get far away from the equator the risk of lung cancer increases. Also, in countries with higher cloud cover were associated with higher rates of the disease.

According to the researchers there may be an explanation for this lower risk of lung cancer observed in places with high light exposure. The explanation may be chemical. Vitamin D, a known protector of cancer, is activated by sunlight (laboratory research has shown that vitamin D can halt tumor growth).

The authors believe that in places with higher exposure to sunlight induces a higher concentration of vitamin D on the human body that may exert a protective effect on cell and tissue, hence the lower incidences of lung cancers in those places.

Lung cancer kills over a million people every year around the globe. In both, men and women, cigarette smoking was associated with higher rates of lung cancer. But after adjusting for this factor a clear beneficial effect of sunlight exposure was seen statistically.

Source:

S B Mohr, C F Garland, E D Gorham, W B Grant, F C Garland. Could ultraviolet B irradiance and vitamin D be associated with lower incidence rates of lung cancer? J Epidemiol Community Health 2008;62:69-74. Abstract URL: http://jech.bmj.com/cgi/content/abstract/62/1/69; URL full report http://press.psprings.co.uk/jech/december/69_ch52571.pdf