Is high vitamin B12 status a cause of lung cancer?

Vitamin B supplementation can have side effects for human health, including cancer risk. We aimed to elucidate the role of vitamin B12 in lung cancer etiology via direct measurements of pre-diagnostic circulating vitamin B12 concentrations in a nested case-control study, complemented with a Mendelian randomization (MR) approach in an independent case-control sample. We used pre-diagnostic biomarker data from 5183 case-control pairs nested within 20 prospective cohorts, and genetic data from 29,266 cases and 56,450 controls. Exposures included directly measured circulating vitamin B12 in pre-diagnostic blood samples from the nested case-control study, and 8 single nucleotide polymorphisms associated with vitamin B12 concentrations in the MR study. Our main outcome of interest was increased risk for lung cancer, overall and by histological subtype, per increase in circulating vitamin B12 concentrations. We found circulating vitamin B12 to be positively associated with overall lung cancer risk in a dose response fashion (odds ratio for a doubling in B12 [ORlog2B12 ] = 1.15, 95% confidence interval (95%CI) = 1.06-1.25). The MR analysis based on 8 genetic variants also indicated that genetically determined higher vitamin B12 concentrations were positively associated with overall lung cancer risk (OR per 150 pmol/L standard deviation increase in B12 [ORSD ] = 1.08, 95%CI = 1.00-1.16). Considering the consistency of these two independent and complementary analyses, these findings support the hypothesis that high vitamin B12 status increases the risk of lung cancer.

Factors associated with vitamin D deficiency in a Norwegian population: the HUNT Study.

Vitamin D deficiency occurs worldwide. Winter season and high Body Mass Index (BMI) are associated with low levels of serum 25-hydroxyvitamin D (25(OH)D). We estimated the prevalence of vitamin D deficiency in a Norwegian adult population and examined factors associated with vitamin D deficiency. A cohort of 25, 616 adults (19-55 years) who participated in both the second and third Nord-Trøndelag Health Study (HUNT 2 (1995-1997) and HUNT 3 (2006-2008)) was established in a previous study. A 10% random sample of the cohort population was recruited for serum 25(OH)D measurements (n=2584), which was used for the current cross-sectional study. Vitamin D deficiency was defined as serum 25(OH)D level <50 nmol/L. The overall prevalence of vitamin D deficiency was 40%, but varied by season (winter: 64%; summer: 20%). Winter season (adjusted prevalence ratio (PR): 3.16, 95% CI 2.42 to 4.12) and obesity (BMI ≥30.0 kg/m2) (PR: 1.74, 95% CI 1.45 to 2.10) were strongly associated with prevalent vitamin D deficiency. Current smoking also demonstrated an increased PR (1.41, 95% CI 1.21 to 1.65). Daily intake of cod liver oil (PR: 0.60, 95% CI 0.41 to 0.77), increased physical activity (PR: 0.80, 95% CI 0.68 to 0.95) and more frequent alcohol consumption (PR: 0.76, 95% CI 0.60 to 0.95) were associated with a reduced PR. The prevalence of vitamin D deficiency was high in Norwegian adults. Winter season, high BMI and current smoking were positively associated, and intake of cod liver oil, increased physical activity and more frequent alcohol consumption were inversely associated with vitamin D deficiency.