Colorectal cancerExposure to sunlight

Lower rates of colorectal cancer are seen in areas that have more sunlight 

Strong inverse correlations between solar UVB and colorectal cancer have been found in numerous ecological studies in the United States1 2 3 4 5 6.

The more recent studies included a number of other risk-modifying factors in the analysis including alcohol consumption, smoking, and urban/rural residence.

In Japan, there was an increase in colorectal cancer with decreasing annual solar radiation7.

In Spain, non-melanoma skin cancer mortality rate, an index of lifetime solar UVB irradiance, was significantly inversely correlated with colon and rectal cancer for both males and females; however, latitude was inversely correlated only with rectal cancer8.

Note that ecological studies integrate the effect of solar UVB and vitamin D throughout the entire lifetime.

Page last edited: 22 August 2011


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