RESULTS The meta- analysis of observational studies showed a weaker slope of dose-response relations than the meta- analysis of RCTs .
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 population
BACKGROUND Many r and omized 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 systematic ally review ed 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 .
Complex Multivitamin Supplementation Improves Homocysteine and Resistance to LDL-C Oxidation
Objective : We previously reported in an open-label pilot trial that a 24-ingredient multivitamin formula favorably influenced homocysteine concentration and LDL-C oxidation indices following 24 weeks of supplementation . Our current aim was to more thoroughly examine this same formula in a r and omized , placebo-controlled , clinical study . Methods : We examined 182 participants for selected plasma vitamin concentrations and clinical ly relevant variables including homocysteine , lipids and LDL-C oxidation indices at baseline and six months . Results : We found no significant differences between groups for any parameter at baseline . Following six months of vitamin supplementation , we observed elevations in plasma concentrations of vitamin B6 ( as pyridoxal 5′-phosphate ; PLP ) , vitamin B12 , folate , vitamin C , vitamin E and β-carotene ( p < 0.0001 ) , all of which were significantly greater than respective placebo group changes ( p < 0.0001 ) . Homocysteine decreased in the treatment ( 8.38 ± 2.9 vs. 6.93 ± 2.5 μmol/L ; p < 0.0001 ) and placebo group ( 8.17 ± 3.0 vs. 7.42 ± 2.2 μmol/L ; p < 0.0001 ) from baseline to six months , respectively , with reductions in the treatment group being greater than placebo ( p < 0.008 ) . LDL-C oxidation indices were also improved as LDL-C oxidation rate was decreased ( −0.39 μmol/min/g protein ; p < 0.0003 ) and LDL-C lag time increased ( 11.3 min ; p < 0.003 ) in supplemented participants . Further analysis also showed that LDL-C oxidation rate was lower ( p < 0.0007 ) and LDL-C lag time longer ( p < 0.0001 ) for the vitamin group than placebo treatment after six months . Conclusion : We conclude that a multi-ingredient vitamin formula with antioxidant properties has measurable effects on homocysteine and LDL-C oxidation indices
RESULTS The meta- analysis of observational studies showed a weaker slope of dose-response relations than the meta- analysis of RCTs .
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 population
BACKGROUND Many r and omized 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 systematic ally review ed 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 .