TABLE 2.
Associations between the MTHFR 677C>T, MTHFR 1793G>A, and MTRR 66A>G SNPs and breast-milk folate vitamer concentrations1
| SNP | Genotype | % (n) | Total folate2 (nmol/L) | Reduced folates3 (nmol/L) | 5-methyl-THF (nmol/L) | UMFA (nmol/L) | UMFA prevalence (%)4 |
|---|---|---|---|---|---|---|---|
| MTHFR 677C>T | C|C | 42.8 (235) | 115.2 ± 2.7 | 72.7 ± 2.0 | 50.4 ± 1.5 | 42.5 ± 2.3 | 94.0 |
| C|T | 48.1 (264) | 121.1 ± 2.8 | 71.6 ± 2.1 | 49.5 ± 1.6 | 49.5 ± 2.3 | 97.3 | |
| T|T | 9.1 (50) | 123.5 ± 6.6 | 67.0 ± 4.1 | 45.5 ± 2.6 | 56.4 ± 4.9 | 100.0 | |
| R 2 | — | 0.005 | 0.002 | 0.002 | 0.01 | — | |
| P | — | 0.10 | 0.32 | 0.24 | 0.004 | 0.05 | |
| MTHFR 1793G>A | G|G | 90.2 (496) | 116.0 ± 0.9 | 69.4 ± 0.6 | 47.9 ± 0.5 | 46.6 ± 0.7 | 96.6 |
| A|G | 9.6 (53) | 124.5 ± 2.3 | 79.7 ± 1.9 | 55.9 ± 1.4 | 44.8 ± 2.3 | 92.5 | |
| A|A | 0.2 (1) | 117.3 ± 0.0 | 56.1 ± 0.0 | 32.9 ± 0.0 | 61.2 ± 0.0 | 100 | |
| R 2 | — | 0.003 | 0.008 | 0.008 | <0.001 | — | |
| P | — | 0.19 | 0.04 | 0.04 | 0.82 | 0.32 | |
| MTRR 66A>G | A|A | 23.8 (131) | 112.0 ± 1.5 | 67.2 ± 1.1 | 47.8 ± 0.9 | 44.8 ± 1.3 | 93.9 |
| A|G | 49.4 (272) | 117.2 ± 2.8 | 68.7 ± 2.0 | 47.1 ± 1.5 | 48.5 ± 2.3 | 97.4 | |
| G|G | 26.9 (148) | 120.2 ± 3.4 | 76.2 ± 2.6 | 52.1 ± 1.8 | 44.0 ± 2.9 | 95.9 | |
| R 2 | — | 0.004 | 0.01 | 0.005 | <0.001 | — | |
| P | — | 0.12 | 0.02 | 0.12 | 0.81 | 0.22 |
Genotyping data were available for 549 (MTHFR 677C>T), 550 (MTHFR 1793G>A), and 551 (MTRR 66A>G) individuals. Data are presented as mean ± SE or percentage. Associations were assessed using the Wald's test using PLINK. Associations were considered significant if P ≤ 0.01 based on Bonferroni correction for multiple testing. THF, tetrahydrofolate; UMFA, unmetabolized folic acid.
Total folate represents the sum of folic acid, THF, 5-methyl-THF, 5,10-methenyl-THF, and 5-formyl-THF.
Reduced folates represents the sum of THF, 5-methyl-THF, 5,10-methenyl-THF, and 5-formyl-THF.
The limit of detection for UMFA was <0.9 nmol/L. Differences in frequencies were assessed by chi-square test and considered significant if P ≤ 0.01 based on Bonferroni correction for multiple testing.