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 .
Lowering homocysteine with B vitamins has no effect on biomarkers of bone turnover in older persons: a 2-y randomized controlled trial.
BACKGROUND In recent prospect i ve studies , higher homocysteine concentrations were shown to be a risk factor for osteoporotic fractures in older persons . Supplements containing folate and vitamins B-12 and B-6 lower homocysteine concentrations . OBJECTIVE The objective of the study was to determine in healthy older persons whether lowering homocysteine with B vitamins affects plasma biomarkers of bone turnover . DESIGN Healthy older persons ( n = 276 ; aged > or=65 y ) were r and omly assigned to receive either a daily supplement containing folate ( 1 mg ) , vitamin B-12 ( 500 microg ) , and vitamin B-6 ( 10 mg ) or a placebo for 2 y. Of these participants , we selected 135 with baseline homocysteine concentrations > 15.0 micromol/L , and we measured serum bone-specific alkaline phosphatase , a marker of bone formation , and bone-derived collagen fragments , a marker of bone resorption , at baseline and 2 y later . RESULTS At 2 y , plasma homocysteine concentrations were 5.2 mumol/L ( 95 % CI : 3.9 , 6.6 micromol/L ; P < 0.001 ) lower in the vitamin than in the placebo group . No significant differences were found in either serum bone-specific alkaline phosphatase ( -0.3 microg/L ; 95 % CI : -2.8 , 2.1 microg/L ; P = 0.79 ) or bone-derived collagen fragments ( -0.0 microg/L ; 95 % CI : -0.1 , 0.1 microg/L ; P = 0.76 ) between the vitamin and placebo groups , respectively , with 2 y of supplementation . CONCLUSION Supplementation with folate and vitamins B-6 and B-12 lowered plasma homocysteine but had no beneficial effect on bone turnover at the end of 2 y , as assessed by biomarkers of bone formation and resorption
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 .