Search

Background: Many randomized controlled trials (RCTs) and observational studies have provided information on the association between vitamin B-12 intake and biomarkers. The use of these data to estimate dose-response relations provides a useful means to summarize the body of evidence. Objective: We systematically reviewed studies that investigated vitamin B-12 intake and biomarkers of vitamin B-12 status and estimated dose-response relations with the use of a meta-analysis. Design: This systematic review included all RCTs, prospective cohort studies, nested case-control studies, and cross-sectional studies in healthy adult populations published through January 2010 that supplied or measured dietary vitamin B-12 intake and measured vitamin B-12 status as serum or plasma vitamin B-12, methylmalonic acid (MMA), or holotranscobalamin. We calculated an intake-status regression coefficient () for each individual study and calculated the overall pooled and SE () by using random-effects meta-analysis on a double-log scale. Results: The meta-analysis of observational studies showed a weaker slope of dose-response relations than the meta-analysis of RCTs. The pooled dose-response relation of all studies between vitamin B-12 intake and status indicated that a doubling of the vitamin B-12 intake increased vitamin B-12 concentrations by 11% (95% CI: 9.4%, 12.5%). This increase was larger for studies in elderly persons (13%) than in studies in adults (8%). The dose-response relation between vitamin B-12 intake and MMA concentrations indicated a decrease in MMA of 7% (95% CI: -10%, -4%) for every doubling of the vitamin B-12 intake. The assessment of risk of bias within individual studies and across studies indicated risk that was unlikely to seriously alter these results. Conclusion: The obtained dose-response estimate between vitamin B-12 intake and status provides complementary evidence to underpin recommendations for a vitamin B-12 intake of populations.

BACKGROUND: Mandatory fortification of flour with folic acid has reduced the number of neural tube defects in North America. Concerns that high intakes of folic acid might mask vitamin B-12 deficiency in older persons have delayed the introduction of fortification in many European countries. Cofortification of flour with folic acid and vitamin B-12 could simultaneously improve folate and vitamin B-12 status. OBJECTIVE: The objective was to estimate the effect of the consumption of bread fortified with modest amounts of folic acid and vitamin B-12 on folate and vitamin B-12 status in healthy older persons living in the Netherlands, where folic acid fortification is not taking place. DESIGN: Men and women aged 50-75 y were randomly assigned in this 12-wk double-blind, placebo-controlled trial to consume bread fortified with 138 mug folic acid and 9.6 mug vitamin B-12 daily (n = 72) or unfortified bread (n = 70). RESULTS: The consumption of fortified bread increased serum folate concentrations by 45% (mean: 6.3 nmol/L; 95% CI: 4.5, 8.1 nmol/L) and serum vitamin B-12 concentrations by 49% (mean: 102 pmol/L; 95% CI: 82, 122 pmol/L) relative to the placebo group. Fortified bread increased erythrocyte folate concentrations by 22% and holotranscobalamin concentrations by 35%; it decreased homocysteine concentrations by 13% and methylmalonic acid concentrations by 10%. Consumption of fortified bread decreased the proportion of individuals with marginal serum vitamin B-12 concentrations (