Inadequate Exposure to UV Light Ups Colorectal Cancer Risk

Low exposure to UVB light could increase the risk of colorectal cancer, according to a study published in the journal BMC Public Health.

Researchers at the University of California San Diego, USA assessed links between global levels of UVB light in 2017 and rates of colorectal cancer for different countries and age groups in 2018.

‘More studies should be done to know potential benefits of correcting vitamin D deficiencies, especially in older age groups.’
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Lower UVB exposure was significantly correlated with higher rates of colorectal cancer across all age groups from 0 to over 75 years in people living in the 186 countries included in the study.

The link remained significant for those aged above 45 after other factors, like skin pigmentation, life expectancy and smoking were also considered. Data on these factors were available for 148 countries.

Lower UVB exposure may decrease levels of vitamin D, which may be associated with an increased risk of colorectal cancer. More studies should be done to know potential benefits of correcting vitamin D deficiencies, especially in older age groups, as per authors.

Raphael Cuomo, co-author of the study said: "Differences in UVB light accounted for a large amount of the variation we saw in colorectal cancer rates, especially for people over age 45. Although this is still preliminary evidence, it may be that older individuals, in particular, may reduce their risk of colorectal cancer by correcting deficiencies in vitamin D."

UVB estimates were obtained by the NASA EOS Aura spacecraft in April 2017 and data on colorectal cancer rates in 2018 for 186 countries from the Global Cancer (GLOBOCAN) database.

Researchers collected data for 148 countries on skin pigmentation, life expectancy, smoking, stratospheric ozone (a naturally-occurring gas that filters the sun's radiation).

Norway, Denmark and Canada, while countries with higher UVB included United Arab Emirates, Sudan, Nigeria, and India has lower UVB.

Colorectal Cancer - Types, Causes, Risk Factors, Symptoms, Diagnosis, Treatment, Prognosis & Prevention
Colorectal cancer is a cancer that starts in the colon or the rectum. Colorectal cancer is the third most common cancer in men.

Intake of vitamin D supplements, clothing and air pollution were not considered in the study.

Observational nature of the study does not allow for conclusions about cause and effect and more work is needed to understand the relationship between UVB and vitamin D with colorectal cancer in more detail.

Source-Medindia