Building on a long-standing observation linking vitamin D deficiency to increased risk of colorectal cancer, a new study from University of California San Diego has found countries where people experience lower levels of UVB light often report higher rates of colorectal cancer.
For several years, researchers have detected a strong correlation between low vitamin D levels and colorectal cancer. However, some studies have questioned that link, finding little evidence of a relationship between cancer and vitamin D.
This new study took a slightly different approach, looking at global levels of UVB light exposure across 186 countries. The researchers accounted for several confounding factors, such as skin pigmentation and smoking, while also adjusting for age.
The study detected a distinct age-dependent inverse association between colorectal cancer and UVB exposure. Above the age of 45 the association was noted as statistically significant.
"Differences in UVB light accounted for a large amount of the variation we saw in colorectal cancer rates, especially for people over age 45,” explains Raphael Cuomo, co-author on the new study. “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."
A 2013 study found a similar relationship between UVB exposure and colorectal cancer, and the results of this new study are in line with those prior findings.
Adding an age-dependent assessment into the new research suggests vitamin D deficiency plays a greater role in the onset of colorectal cancer primarily in older individuals. The researchers hypothesize this could be due to chronic vitamin D deficiency increasing one’s colorectal cancer risk.
“This study supports the need for adequate public health programs to avoid vitamin D inadequacy at national and global levels, whether through screening those at risk, through selective supplementation, or through population-based measures such as food fortification,” the researchers conclude in the new study. “Future studies can aim at identifying the cancer types which show significant improvement with vitamin D supplementation.”
The new study was published in the journal BMC Public Health.
Source: BMC Public Health