HomocysteineFolic AcidVitamin B 12Vitamin B ComplexHyperhomocysteinemiaMethylenetetrahydrofolate Reductase (NADPH2)Oxidoreductases Acting on CH-NH Group DonorsVitamin B 12 DeficiencyFolic Acid DeficiencyVitamin B 6RiboflavinPyridoxineFood, FortifiedDietary SupplementsMethionineMethylmalonic AcidFastingGenotypeErythrocytesPlasmaDietRisk FactorsPolymorphism, GeneticCreatinineCross-Sectional StudiesPlasma Cells