The relationships between serum folate, tHcy, and

MTHFR genotypes. The mean tHcy (μM) was plotted separately for each genotype within the 4 quartiles of the folate distribution. (A) Relationship between MTHFR 677C>T genotypes, folate, and tHcy. Folate concentrations increase from quartile 1 to quartile 4. Quartile 1: 9.50 nM or less; quartile 2: 9.51 to 12.95 nM; quartile 3: 12.96 to 18.83 nM; and quartile 4: 18.84 nM or more. (B) Relationship between composite MTHFR 677C>T and 1298A>C genotypes, folate, and tHcy. Folate quartiles are identical to those described in panel A.