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 .
Vitamins B6 and B12 and folate status in an adult Mediterranean population
Objective : To assess the nutritional status for vitamins B6 and B12 and folate in an adult Mediterranean population , in order to identify patterns of intake , groups at risk for deficiency , and factors that might influence this risk . Design : A cross-sectional epidemiological survey . Setting : And alusia , a western Mediterranean region in southern Spain . Subjects : The study was carried out with a r and om sample of 3528 subjects ( 1813 men , 1715 women ) who were between 25 and 60 y of age .  Blood sample s were obtained for biochemical assays in a r and om sub sample of 384 subjects ( 183 men , 201 women ) . Interventions :  Food consumption was assessed by 48-h recall .  Vitamin B6 was measured as alpha erythrocyte aspartate aminotransferase activation coefficient ( αEAST ) ; vitamin B12 and folate concentrations were measured in plasma . Results : Energy and vitamin intakes were significantly higher in men than in women . In men , intakes were below two-thirds of the RDA in 10.8 , 2.9 and 22.6 % for B6 , B12 and folate , respectively . The corresponding figures in women were 16.7 , 5.1 and 23.5 % for vitamins B6 , B12 and folate . Age , place of residence and educational level , alcohol use and smoking were also associated with differences in the intake of these nutrients . Biochemical analyses showed that vitamins B6 , B12 and folate status was acceptable in 75.7 , 89.1 and 57.6 % of the population , respectively . Plasma concentration of folate was significantly higher in women . Conclusion : Our results provide a precise estimate of the nutritional status for vitamins B6 , B12 and folate in the adult population of southern Spain . Factors such as age , place of residence , level of education and smoking can increase the risk of inadequate intake of some nutrients . However , these factors did not affect biochemical indexes of nutritional status in the present study .Sponsorship : Dirección General de Salud Pública and the Health Council of the And alusian Regional Government
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 .