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 .
Nutrient-dense foods and exercise in frail elderly: effects on B vitamins, homocysteine, methylmalonic acid, and neuropsychological functioning.
BACKGROUND Frail elders are at risk of suboptimal micronutrient status , functional decline , and neurologic disorders . The influence of oral multimicronutrients in physiologic doses and of moderately intense physical exercise on homocysteine ( Hcy ) , methylmalonic acid ( MMA ) , and neurologic functioning have not yet been investigated . OBJECTIVE Our goal was to determine the effects of enriched foods and exercise on blood vitamins , Hcy , MMA , and neuropsychological functioning in the frail . DESIGN A 17-wk r and omized controlled intervention trial was used to study 1 ) enriched foods plus a social program , 2 ) regular foods plus exercise , 3 ) enriched foods plus exercise , and 4 ) regular foods plus a social program . Enriched foods contained multiple micronutrients ( 25 - 100 % of the Dutch recommended dietary allowances ) ; exercises focused on strength , coordination , flexibility , and endurance . Vitamin ( cobalamin , red blood cell folate , and pyridoxal 5'-phosphate ) , Hcy , and MMA concentrations were measured and 2 neuropsychological tests were conducted . RESULTS Vitamin concentrations were higher in the supplemented groups than in the unsupplemented groups ( P < 0.001 ; total n = 130 ) . Compared with baseline , cobalamin in the supplemented groups was increased by 22 % , plasma folate by 101 % , red blood cell folate by 87 % , and pyridoxal 5'-phosphate by 68 % . Concentrations in the unsupplemented groups changed by -2 % , -6 % , 1 % , and -13 % , respectively . Hcy decreased by 25 % and MMA by 30 % in the supplemented groups , compared with a small increase in Hcy ( 2 % ) and decrease in MMA ( 9 % ) in the unsupplemented groups . Exercise did not significantly affect vitamin , Hcy , or MMA concentrations . No significant effect of either intervention was observed on the neuropsychological tests . CONCLUSIONS The decrease in Hcy and MMA in frail elders confirms a sub clinical metabolic deficiency state . Enriched foods containing physiologic amounts of micronutrients have a beneficial effect on these metabolites . No effects of B vitamins on mental health were identified
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 .