The association between dietary vitamin B₁₂and lung cancer risk: findings from a prospective cohort study

Background Since previous epidemiological studies reported inconsistent associations between dietary vitamin B₁₂intake and lung cancer risk, more studies are warranted to clarify this association in different populations. Methods The association between dietary B₁₂intake and lung cancer risk was examined in the Singapore Chinese Health Study, an ongoing prospective cohort study of 63 257 Singaporean Chinese men and women, 45-74 years of age at enrollment during 1993-1998 and were followed up for incidence of lung cancer for up to 25 years. Dietary vitamin B₁₂intake was derived from a validated food frequency questionnaire. Cox proportional hazard regression method was used to estimate hazard ratio and 95% confidence interval (CI) of lung cancer associated with dietary vitamin B₁₂intake with adjustment for multiple potential confounders. Results After a mean follow-up of 17.64 years, 2001 study participants developed lung cancer. High levels of vitamin B₁₂intake were associated with significantly increased risk of lung cancer (P_trend= 0.03). Compared with the lowest quintile, hazard ratios (95% CIs) of lung cancer for quintile 2, 3, 4, and 5 of vitamin B₁₂intake were 1.09 (0.95-1.25), 1.11 (0.96-1.28), 1.11 (0.97-1.29) and 1.18 (1.03-1.35), respectively. This positive association was more apparent in men than in women, in adenocarcinoma patients, or in participants with equal or less than 2 years follow-up than those with longer duration of follow-up. Conclusion Higher intake of dietary vitamin B₁₂was associated with increased risk of lung cancer. This highlights the potential harmful effect of vitamin B₁₂supplementation for lung cancer.