Long-term effects of folic acid and vitamin-B12 supplementation on fracture risk and cardiovascular disease: Extended follow-up of the B-PROOF trial

Background & aims: In the initial B-proof, we found inconsistent results of B vitamin supplementation. However, the debate regarding the effects of B vitamins on age-related diseases continues. Therefore, our aim was to investigate the long-term effects (5–7 years follow-up) of an intervention with folic acid and vitamin-B12 supplementation on fracture and cardiovascular disease risk. Methods: Extended follow-up of the B-PROOF trial, a multi-center, double-blind randomized placebo-controlled trial designed to assess the effect of 2–3 years daily supplementation with folic acid (400 μg) and vitamin-B12 (500 μg) versus placebo (n = 2,919). Primary outcome was verified self-reported fracture incidence and secondary outcomes were self-reported cardiovascular endpoints, which were collected through a follow-up questionnaires Proportional hazard analyses was used for the effect of the intervention on risk of fracture(s) and logistic regression for the effect of the intervention on risk of cardiovascular disease. Results: A total of 1,298 individuals (44.5%) participated in the second follow-up round with median of 54 months [51–58], (n = 662 and n = 636, treatment versus placebo group). Median age at baseline was 71.0 years [68.0–76.0] for both groups. No effect was observed of the intervention on osteoporotic fracture or any fracture risk after a follow-up (HR: 0.99, 95% CI: 0.62–1.59 and HR: 0.77; 95% CI: 0.50–1.19, respectively), nor on cardiovascular or cerebrovascular disease risk (OR: 1.05; 95%CI: 0.80–1.44 and OR: 0.85; 95%CI: 0.50–1.45, respectively). Potential interaction by baseline homocysteine concentration was observed for osteoporotic- and any fracture (p = 0.10 and 0.06 respectively), which indicated a significantly lower risk of any fracture in the treatment group with higher total homocysteine concentrations (>15.1 μmol/l). No age-dependent effects were present. Conclusions: This study supports and extends previous null-findings of the B-PROOF trial and shows that supplementation of folic acid and vitamin-B12 has no effect on fracture risk, nor on cardiovascular disease in older individuals over a longer follow-up period. However, B-vitamin supplementation may be beneficial in reducing fractures in individuals with high total homocysteine concentrations, a finding which needs to be replicated