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 .
Reduction of plasma homocysteine and serum methylmalonate concentrations in apparently healthy elderly subjects after treatment with folic acid, vitamin B12 and vitamin B6: a randomised trial
Objectives : To investigate , in an elderly population : ( 1 ) the effects of oral B-vitamin therapy on P-tHcys , S-MMA and Hb/MCV , ( 2 ) the appropriate decision limit for ‘ high ’ metabolite concentrations and ( 3 ) the estimated prevalence of vitamin B12/folate deficiency on the basis of different decision limits . Design : Double-blind placebo-controlled intervention study . Setting : Outpatient clinic . Subjects : A total of 209 community-dwelling subjects , median age 76 y ( range 70–93 ) y. Interventions : Four months of oral daily supplementation with 0.5 mg cyanocobalamin , 0.8 mg folic acid and 3 mg vitamin B6 . Results : High P- tHcys was found in 64 % of men and 45 % of women , high S-MMA in 11 % of both . Vitamin B12 deficiency was observed in 7.2 % and folate deficiency in 11 % of all subjects . Health-related upper reference limits for the metabolites at the start were higher than the laboratory 's upper reference limits . The latter were , however , similar to those of the vitamin replete group . There was a significant decrease in P-tHcys ( P<0.001 ) and S-MMA ( P=0.009 ) after 4 months of vitamin treatment . In a multivariate analysis , the P-Hcys change correlated positively with baseline P-tHcys and inversely with baseline P-folate and transferrin saturation ( Fe/TIBC ratio ) . The S-MMA change correlated with baseline S-MMA and inversely with baseline vitamin B12 and age . Conclusions : Suboptimal vitamin status is an important cause of elevated P-tHcys and S-MMA in apparently healthy elderly subjects .  Oral B-vitamin therapy is an effective and convenient way to normalise P-tHcys and S-MMA.Sponsorship : Support — Recip AB
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 .