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 .
Multivitamin/mineral supplementation improves plasma B-vitamin status and homocysteine concentration in healthy older adults consuming a folate-fortified diet.
Elevated homocysteine has been identified as an independent risk factor for cardiovascular and cerebrovascular disease . Although multivitamin use has been associated with low plasma homocysteine concentrations in several observational studies , no clinical trials have been conducted using multivitamin/mineral supplements to lower homocysteine . We determined whether a multivitamin/mineral supplement formulated at about 100 % Daily Value will further lower homocysteine concentration and improve B-vitamin status in healthy older adults already consuming a diet fortified with folic acid . In this r and omized , double-blind , placebo-controlled trial , 80 free-living men and women aged 50 - 87 y with total plasma homocysteine concentrations of > or = 8 micromol/L received either a multivitamin/mineral supplement or placebo for 56 d while consuming their usual diet . After the 8-wk treatment , subjects taking the supplement had significantly higher B-vitamin status and lower homocysteine concentration than controls ( P : < 0.01 ) . Plasma folate , pyridoxal phosphate ( PLP ) and vitamin B-12 concentrations were increased 41.6 , 36.5 and 13.8 % , respectively , in the supplemented group , whereas no changes were observed in the placebo group . The mean homocysteine concentration decreased 9.6 % in the supplemented group ( P : < 0.001 ) and was unaffected in the placebo group . There were no significant changes in dietary intake during the intervention . Multivitamin/mineral supplementation can improve B-vitamin status and reduce plasma homocysteine concentration in older adults already consuming a folate-fortified diet
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 .