Folate vs. Folic Acid: MTHFR, Methylation & Why It Matters

Few nutrients have generated as much confusion as vitamin B9. The terms "folate" and "folic acid" are often used interchangeably, but they're not the same thing — and the distinction has real implications for a significant percentage of the population.

Folate vs. Folic Acid

Folate is the naturally occurring form of vitamin B9 found in foods like leafy greens, legumes, and liver. Folic acid is the synthetic form used in supplements and fortified foods. Folic acid must be converted by the enzyme dihydrofolate reductase (DHFR) into usable forms, and then further processed by the MTHFR enzyme into 5-methyltetrahydrofolate (5-MTHF) — the biologically active form.

The MTHFR Factor

The MTHFR gene encodes the methylenetetrahydrofolate reductase enzyme. Common genetic variants (especially C677T and A1298C) reduce this enzyme's activity by 30-70%, depending on whether someone carries one or two copies of the variant. Roughly 10-15% of some populations are homozygous for C677T, meaning their MTHFR enzyme operates at about 30% of normal capacity.

For these individuals, supplementing with methylfolate (5-MTHF) instead of folic acid bypasses the MTHFR bottleneck entirely. Many practitioners now recommend methylfolate as the default supplemental form.

Folate's Role in Methylation

5-MTHF donates a methyl group to convert homocysteine back into methionine (which is then converted to SAMe, the body's primary methyl donor). This makes folate a cornerstone of the methylation cycle. Vitamin B12 and B6 are also required for this cycle to function properly.

Food Sources

The best food sources of natural folate include chicken liver, lentils, black-eyed peas, spinach, asparagus, broccoli, and avocado. Cooking reduces folate content significantly, especially in leafy greens. In many countries, flour and cereal grains are fortified with folic acid to prevent neural tube defects.

External resources: Linus Pauling Institute — Folate