For smokers, low levels of vitamin D may lead to cancer

In the U.S. alone, cigarette smoking accounts for more deaths annually than HIV, illegal drugs, alcohol, motor vehicle injuries, suicides, and murders combined. It is the primary causal factor for at least 30% of all cancer deaths, and can lead to multiple kinds of cancer, including bladder, cervical, esophageal, head and neck, kidney, liver, lung, pancreatic, and stomach, as well as myeloid leukemia. According to the Centers for Disease Control and Prevention, the healthcare expenditures and productivity losses due to smoking cost the economy approximately $193 billion per year.

In this paper, Afzal et al. measured plasma vitamin D levels in blood samples collected in 1981-1983 from 10,000 Danes from the general population. Researchers then followed the study participants for up to 28 years through the Danish Cancer Registry. Of the participants, 1,081 eventually developed a tobacco-related cancer. The authors determined that the median vitamin D concentration among these participants was only 14.8 ng/mL, versus the higher 16.4 ng/mL median concentration found for all participants together.

These results show for the first time that the risk of tobacco-related cancers as a group is associated with lower concentrations of vitamin D. The data also indicate that tobacco smoke chemicals may influence vitamin D metabolism and function, while vitamin D may conversely modify the carcinogenicity of tobacco smoke chemicals. If further research confirms this, it would be consistent with previous studies demonstrating the anti-tumorigenic effects of vitamin D derivatives, as well as the correlation of vitamin D deficiency with favorable cancer-forming conditions and increased susceptibility to tobacco smoke carcinogens. Interestingly, though, low vitamin D levels were not connected with risk of other cancer types.

"Our analyses show that the association between lower concentrations of plasma vitamin D and higher risk of cancer may be driven by tobacco-related cancer as a group, which has not been shown before," stated author Børge G. Nordestgaard, MD, DMSc, in the paper. "This is important for future studies investigating the association between plasma vitamin D and risk of cancer."