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Background: Disturbed folate metabolism is associated with an increased risk of some cancers. Our objective was to determine whether blood levels of folate, vitamin B(12), and related metabolites were associated with prostate cancer risk., Methods: Matched case-control study nested within the U.K. population-based Prostate testing for cancer and Treatment (ProtecT) study of prostate-specific antigen-detected prostate cancer in men ages 50 to 69 years. Plasma concentrations of folate, B(12) (cobalamin), holo-haptocorrin, holo-transcobalamin total transcobalamin, and total homocysteine (tHcy) were measured in 1,461 cases and 1,507 controls. ProtecT study estimates for associations of folate, B(12), and tHcy with prostate cancer risk were included in a meta-analysis, based on a systematic review., Results: In the ProtecT study, increased B(12) and holo-haptocorrin concentrations showed positive associations with prostate cancer risk [highest versus lowest quartile of B(12) odds ratio (OR) = 1.17 (95% confidence interval, 0.95-1.43); P(trend) = 0.06; highest versus lowest quartile of holo-haptocorrin OR = 1.27 (1.04-1.56); P(trend) = 0.01]; folate, holo-transcobalamin, and tHcy were not associated with prostate cancer risk. In the meta-analysis, circulating B(12) levels were associated with an increased prostate cancer risk [pooled OR = 1.10 (1.01-1.19) per 100 pmol/L increase in B(12); P = 0.002]; the pooled OR for the association of folate with prostate cancer was positive [OR = 1.11 (0.96-1.28) per 10 nmol/L; P = 0.2) and conventionally statistically significant if ProtecT (the only case-control study) was excluded [OR = 1.18 (1.00-1.40) per 10 nmol/L; P = 0.02]., Conclusion: Vitamin B(12) and (in cohort studies) folate were associated with increased prostate cancer risk., Impact: Given current controversies over mandatory fortification, further research is needed to determine whether these are causal associations., (Copyright 2010 AACR.)

Context: Recently, concern has been raised about the safety of folic acid, particularly in relation to cancer risk., Objective: To evaluate effects of treatment with B vitamins on cancer outcomes and all-cause mortality in 2 randomized controlled trials., Design, Setting, and Participants: Combined analysis and extended follow-up of participants from 2 randomized, double-blind, placebo-controlled clinical trials (Norwegian Vitamin Trial and Western Norway B Vitamin Intervention Trial). A total of 6837 patients with ischemic heart disease were treated with B vitamins or placebo between 1998 and 2005, and were followed up through December 31, 2007., Interventions: Oral treatment with folic acid (0.8 mg/d) plus vitamin B(12) (0.4 mg/d) and vitamin B(6) (40 mg/d) (n = 1708); folic acid (0.8 mg/d) plus vitamin B(12) (0.4 mg/d) (n = 1703); vitamin B(6) alone (40 mg/d) (n = 1705); or placebo (n = 1721)., Main Outcome Measures: Cancer incidence, cancer mortality, and all-cause mortality., Results: During study treatment, median serum folate concentration increased more than 6-fold among participants given folic acid. After a median 39 months of treatment and an additional 38 months of posttrial observational follow-up, 341 participants (10.0%) who received folic acid plus vitamin B(12) vs 288 participants (8.4%) who did not receive such treatment were diagnosed with cancer (hazard ratio [HR], 1.21; 95% confidence interval [CI], 1.03-1.41; P = .02). A total of 136 (4.0%) who received folic acid plus vitamin B(12) vs 100 (2.9%) who did not receive such treatment died from cancer (HR, 1.38; 95% CI, 1.07-1.79; P = .01). A total of 548 patients (16.1%) who received folic acid plus vitamin B(12) vs 473 (13.8%) who did not receive such treatment died from any cause (HR, 1.18; 95% CI, 1.04-1.33; P = .01). Results were mainly driven by increased lung cancer incidence in participants who received folic acid plus vitamin B(12). Vitamin B(6) treatment was not associated with any significant effects., Conclusion: Treatment with folic acid plus vitamin B(12) was associated with increased cancer outcomes and all-cause mortality in patients with ischemic heart disease in Norway, where there is no folic acid fortification of foods., Trial Registration: clinicaltrials.gov Identifier: NCT00671346.

Background: Homocysteine is a risk factor for cardiovascular disease. We evaluated the efficacy of homocysteine-lowering treatment with B vitamins for secondary prevention in patients who had had an acute myocardial infarction., Methods: The trial included 3749 men and women who had had an acute myocardial infarction within seven days before randomization. Patients were randomly assigned, in a two-by-two factorial design, to receive one of the following four daily treatments: 0.8 mg of folic acid, 0.4 mg of vitamin B12, and 40 mg of vitamin B6; 0.8 mg of folic acid and 0.4 mg of vitamin B12; 40 mg of vitamin B6; or placebo. The primary end point during a median follow-up of 40 months was a composite of recurrent myocardial infarction, stroke, and sudden death attributed to coronary artery disease., Results: The mean total homocysteine level was lowered by 27 percent among patients given folic acid plus vitamin B12, but such treatment had no significant effect on the primary end point (risk ratio, 1.08; 95 percent confidence interval, 0.93 to 1.25; P=0.31). Also, treatment with vitamin B6 was not associated with any significant benefit with regard to the primary end point (relative risk of the primary end point, 1.14; 95 percent confidence interval, 0.98 to 1.32; P=0.09). In the group given folic acid, vitamin B12, and vitamin B6, there was a trend toward an increased risk (relative risk, 1.22; 95 percent confidence interval, 1.00 to 1.50; P=0.05)., Conclusions: Treatment with B vitamins did not lower the risk of recurrent cardiovascular disease after acute myocardial infarction. A harmful effect from combined B vitamin treatment was suggested. Such treatment should therefore not be recommended. (ClinicalTrials.gov number, NCT00266487.)., (Copyright 2006 Massachusetts Medical Society.)

The article offers information on a study which investigated the effects of treatment with B vitamins on cancer outcomes and all-cause mortality. A total of 6837 patients were recruited to participate in two randomized, double-blind, placebo-controlled clinical trials conducted in Norway between 1998 and 2005, and followed up through December 31, 2007. Treatment interventions included oral treatment with folic acid combined with vitamin B12 and vitamin 6, folic acid combined with vitamin B12, vitamin 6 alone and placebo. Presented in details are the research findings.

The article offers information on a study which investigated the effects of treatment with B vitamins on cancer outcomes and all-cause mortality. A total of 6837 patients were recruited to participate in two randomized, double-blind, placebo-controlled clinical trials conducted in Norway between 1998 and 2005, and followed up through December 31, 2007. Treatment interventions included oral treatment with folic acid combined with vitamin B12 and vitamin 6, folic acid combined with vitamin B12, vitamin 6 alone and placebo. Presented in details are the research findings.