Table 3

 Serum and erythrocyte folate, plasma homocysteine, and markers of DNA methylation before and after supplementation with folic acid or placebo

Folic acid (n = 15)Placebo (n = 16)p Value
MTHFR, methylenetetrahydrofolate reductase; MS, methionine synthase.
Values are arithmetic means (95% confidence interval) adjusted for sex, age, body mass index, smoking, alcohol intake, *MTHFR 677C→T genotype, and †MS 2756A→G genotype.
§n = 14.
¶n = 15.
Serum folate* (μg/l)
    Baseline7.4 (5.7 to 9.2)§8.2 (6.6 to 9.8)
    Follow up13.4 (11.6 to 15.2)§7.3 (5.6 to 8.9)
    Change+6.0 (4.2 to 7.7)§−1.0 (−2.6 to 0.7)<0.001
Erythrocyte folate* (μg/l)
    Baseline282 (227 to 387)316 (261 to 371)¶
    Follow up443 (376 to 511)305 (238 to 373)¶
    Change+161 (114 to 209)−11 (−58 to 7)¶<0.001
Plasma homocysteine*† (μmol/l)
    Baseline12.2 (10.1 to 14.4)§11.5 (9.5 to 13.5)
    Follow up10.7 (8.4 to 13.1)§12.3 (10.2 to 14.5)
    Change−1.5 (−2.5 to −0.5)§+0.8 (−0.1 to 1.8)0.01
[3H] methyl incorporation in leucocyte DNA*† (Bq/μg DNA)
    Baseline748 (672 to 825)678 (605 to 752)
    Follow up515 (440 to 589)655 (583 to 727)
    Change−233 (−349 to −118)−23 (−134 to 88)0.05
[3H] methyl incorporation in colonic DNA*† (Bq/μg DNA)
    Baseline602 (515 to 689)473 (389 to 556)
    Follow up451 (361 to 541)458 (371 to 544)
    Change−151 (−234 to −69)−15 (−95 to 64)0.09