Table 4. Joint effect of MTHFR C677T and plasma folate concentration on PBMC L1 methylation among non-cases.

MTHFR C677T and folatecombination	Number of women with PBMC L1Methylation ≥68.5%/<68.5%	OR (95% CI)	P-value*
CT+TT & folate ≥11.21 ng/mL	22/21	1.00 (ref)
CT+TT & folate <11.21 ng/mL	8/32	0.28 (0.09–0.78)	0.017
CC & folate ≥11.21 ng/mL	39/77	0.55 (0.24–1.25)	0.151
CC & folate <11.21 ng/mL	35/79	0.63 (0.27–1.47)	0.285
P-value for interaction	0.030

*Adjusted for age, self-reported race, level of education, BMI, physical activity smoking status, parity, use of oral/hormone contraceptive and circulating concentrations of vitamin C, total carotene and vitamin B12.