Increased vitamin D levels may protect smokers from cancer

According to a new study from Denmark low blood vitamin D concentrations seem to be related to a higher risk of developing tobacco-related cancers in smokers.

In the observational study, the plasma 25-hydroxyvitamin D [25(OH)D] concentrations in blood samples of 9791 participants were measured at the beginning of the trial and cases of cancer were documented during up to the following 28 years (1). During the study 1081 participants developed a tobacco-related cancer (e.g., lung, head and neck, bladder and kidney cancer) and 1506 developed other cancers. The results showed that smokers who developed cancer had lower average levels of vitamin D (14.8 ng/mL or
37 nmol/L) than the average of all participants (16.4 ng/mL or 41 nmol/L). Vitamin D concentrations
were not associated with the risk of other cancers.

The researchers commented that these findings are biologically plausible because vitamin D has been shown to decrease tumor invasion and metastasis in in vitro studies. In addition, animal models with vitamin D deficiency showed increased susceptibility to tobacco smoke carcinogens. Finally, smoking is associated with reduced 25(OH)D concentrations (2). Experts noted that the observational data remain suggestive rather than conclusive. Further testing in randomized controlled trials would be necessary before vitamin D supplements can be considered for clinical recommendation for cancer risk reduction in smokers (3).

1. fzal S. et al. Low plasma 25-Hydroxyvitamin D and risk of tobacco-related cancer. Clinical Chemistry. 20213; 59:5.
2. International Agency for Research on Cancer (IARC). Tobacco smoke and involuntary smoking. Lyon: IARC; 2004.
3. Cook N. R. Vitamin D and cancer: can we believe the evidence from observational studies? Clinical Chemistry. 20213; 59:5.