Supplementation with B vitamins was associated with an increased risk of lung cancer among men, though not among women, according to a new study. The increased risk was only found with individual supplements, but not from multivitamins.
“We hypothesized that the disturbance of the homeostasis of these vitamins, particular intakes in excess of the Recommended Dietary Allowance (RDA), could have a profound effect on the cellular environment and physiology (including altered oxidative stress and nucleotide pools), thus leading to a harmful consequence such as carcinogenesis,” wrote study authors led by Chi-Ling Chen, PhD, of National Taiwan University in Taipei.
The VITAL cohort included 77,118 individuals, aged 50 to 76 years, recruited between 2000 and 2002. After a mean follow-up of 6 years, there were 808 primary invasive lung cancers found in the cohort. Results of the analysis of this cohort were published online ahead of print in the Journal of Clinical Oncology.
Among men, former users of vitamin B6 individual supplements had a higher risk of lung cancer than nonusers, with a multivariate hazard ratio (HR) of 1.84 (95% CI, 1.01–3.36). This was not the case among women, with an HR of 1.42 (95% CI, 0.84–2.38), and it was not the case when the supplement source was a multivitamin. Men who had the highest 10-year average daily supplement dose had an HR for lung cancer of 1.82 (95% CI, 1.25–2.65) compared with nonusers.
Results were similar for vitamin B12. Former users of individual supplements had an HR for lung cancer of 2.42 (95% CI, 1.49–3.95) compared with nonusers; again, this applied only to men. Those in the highest group of 10-year average dose had an HR for lung cancer of 1.98 (95% CI, 1.32–2.97) compared to nonusers. For both types of B vitamin, the risks were higher among men who smoked at baseline.
“Consistent with prior evidence of harm for other vitamin supplements on lung cancer risk in smokers, the associations we observed provide evidence that high-dose B6 and B12 supplements should not be taken for lung cancer prevention and, in fact, may increase risk of this disease in men,” the authors concluded.