Folic acid vs methylfolate: which form is better (table)

Vitamin B9 participates in DNA synthesis, cell division, and methylation. In a randomized study by the Medical Research Council in 1991, folic acid supplementation started before conception reduced the risk of neural tube defects in women with a previous pregnancy complicated by such a defect by 72%. This is one of the strongest effects demonstrated in nutrition. The trouble begins at the supplement shelf because vitamin B9 is sold in two forms that the body processes differently. Folic acid is synthetic and requires enzymatic conversion. Methylfolate is a ready-to-use form. Below you will find a table of differences, verified thresholds of folate in the blood, upper intake limits, and the cost of a daily portion of vitamin B9 preparations that are actually available.

KEY INFORMATION
• Folic acid before conception reduced the risk of neural tube defects by 72% (MRC Vitamin Study, Lancet 1991).
• Methylfolate bypasses the MTHFR-dependent stage, of which the variant has an allele frequency of about 38% (Frosst et al., 1995).
• The upper limit of folic acid intake for adults is 1000 µg per day (EFSA).
• Six preparations in the catalog declare vitamin B9, two in methylated form.

What is the difference between folic acid and methylfolate?

Folic acid is a synthetic, oxidized form of vitamin B9 that the body must first reduce and methylate before the cell can use it. Methylfolate, or 5-methyltetrahydrofolate, is already an active form and enters metabolism without this conversion. The entire practical difference comes down to one enzyme in this pathway.

This enzyme is methylenetetrahydrofolate reductase, abbreviated as MTHFR. It converts 5,10-methylenetetrahydrofolate into 5-MTHF, which is the dominant form of folate in the blood and a methyl group donor in the conversion of homocysteine to methionine. Frosst and colleagues described a common mutation of the MTHFR gene in 1995, which strongly alters a conserved amino acid residue. In their material, this variant occurred with a frequency of about 38% of unselected chromosomes, reduced enzyme activity, and increased its thermolability, while homozygous individuals had significantly elevated plasma homocysteine levels (Frosst i in., Nature Genetics 1995).

What does this mean when purchasing a supplement? A person with two copies of the variant processes folic acid more slowly, so the same number of micrograms on the label does not represent the same amount of active folate in the cells. Methylfolate enters circulation beyond this bottleneck. It is therefore a more predictable form, regardless of genotype, and this is the entire advantage attributed to it in manufacturers' materials.

Folic acid or methylfolate: what does the comparison table show?

The summary below organizes these differences that truly matter when choosing a preparation: chemical form, dependence on genotype, and behavior at high doses. The data comes from a review of folate prepared for the Nordic Nutrition Recommendations 2023 and from works cited later in the text.

One row of this table is often overinterpreted. The absence of an unmetabolized pool is a biochemical fact, but not proof that folic acid in an acceptable dose harms anyone. The NNR 2023 review states directly that observations indicating adverse effects of high folic acid intake remain ambiguous (Bjørke-Monsen i Ueland, NNR 2023).

Who really needs the methylated form?

Methylated forms are most needed by carriers of the MTHFR variant, especially homozygotes, and individuals with elevated homocysteine. The same review states that with MTHFR polymorphism, serum folate levels should exceed 15 nmol/l, which is higher than the threshold accepted for the general population.

The general threshold is 10 nmol/l: below this value, the World Health Organization recognizes a folate deficiency in an adult. In women of childbearing age, a different indicator is used, namely folate in erythrocytes, and a different threshold, 906 nmol/l. Above this level, the reduction in the risk of neural tube defects is greatest. These are two thresholds answering two different questions: the first addresses deficiency, the second addresses obstetric risk. The authors of the review add that folate status is always assessed together with vitamin B12 concentration, as both vitamins work in the same cycle.

We checked how this difference appears on the labels of products from our catalog, and the conclusion is inconvenient for the buyer. The chemical form is sometimes listed in a completely different place in the description than the quantity. In one of the products, the composition table lists folic acid at a quantity of 37.5 µg, while the adjacent paragraph specifies that folate was added as calcium L-methylfolate. The name in the composition table does not determine the form. The complete list of ingredients does.

How much folate should be taken during pregnancy and from when?

Supplementation begins before conception, as the neural tube closes in the first weeks of pregnancy, often before the pregnancy is recognized. Products for women planning pregnancy are usually dosed at 400 or 800 µg of vitamin B9 per daily serving. The specific dose is determined by the attending physician.

The evidence on which this entire practice is based comes from a study by the Medical Research Council. A randomized trial in 33 centers across seven countries included 1817 women with a history of previous pregnancies affected by neural tube defects. Among the 1195 completed pregnancies, a defect was found in 27 children: six in the groups receiving folic acid and twenty-one in the others. This results in a protective effect of about 72%, with a relative risk of 0.28 (MRC Vitamin Study Research Group, Lancet 1991). The set of the remaining seven vitamins did not yield a significant effect.

Note the dose that was given there: 4000 µg daily, which is four times the upper limit of intake set by EFSA at 1000 µg daily, also for pregnant women. This is not a contradiction, but a boundary between population prevention and intervention for a woman at very high risk. Doses above the limit belong to the physician, not to self-selection from the shelf.

Czy nadmiar kwasu foliowego szkodzi?

For adults and for pregnant women, EFSA sets the upper limit of folic acid intake at 1000 µg daily. For children, the limits are lower and increase with age: from 200 µg at ages 1-3, through 400 µg at ages 7-10, to 800 µg for teenagers aged 15-17.

The most frequently repeated criticism of folic acid concerns masking vitamin B12 deficiency. The NNR 2023 review places this effect much higher than suggested by popular guides: masking hematological symptoms of cobalamin deficiency was only described with intake exceeding 5000 µg daily. The authors also note that adverse effects were reported exclusively for synthetic folic acid, never for folates from food.

A separate issue is unmetabolized folic acid circulating in the blood. Troen and colleagues detected it in 78% of fasting study participants, and the cytotoxicity of NK cells was about 23% lower in women with detectable folic acid. The relationship intensified with concentration and was more pronounced in women over sixty (Troen i in., Journal of Nutrition 2006). The authors themselves describe the conclusion as a premise for further research, not as proof of harm, and the assessment in the NNR 2023 review sounds the same.

What does folate do with homocysteine, stroke, and mood?

Folate lowers homocysteine, and homocysteine is a marker of vascular risk. In an analysis of 1160 participants in the Framingham Heart Study aged 67-96, the concentration of homocysteine showed a strong inverse relationship with the concentration of folate in plasma, and elevated values were found in 29.3% of the subjects.

This same work attributes vitamin B deficiencies to as much as 67% of cases of elevated homocysteine in this population (Selhub i in., JAMA 1993). Does this translate into hard endpoints? A meta-analysis of eight randomized studies showed that folic acid supplementation reduces the risk of stroke by 18%, with the effect being more pronounced with treatment lasting longer than 36 months and in populations without grain fortification, where the relative risk was 0.75 (Wang i in., Lancet 2007). Poland belongs to such populations, as fortifying flour is voluntary here.

The psychiatric aspect requires a more cautious statement than is usually attributed to it. In two double-blind studies, L-methylfolate was added to the treatment of SSRI-resistant depression. A dose of 7.5 mg did not differ from placebo. Only 15 mg daily showed a significant advantage, with a number needed to treat of about six (Papakostas i in., American Journal of Psychiatry 2012). These are therapeutic doses, twenty times higher than supplemental doses.

Which products in the u Bucha offer contain vitamin B9?

We searched the entire store catalog, 386 items, by name and by full description of the composition. No product has folate in its name. Six products declare vitamin B9, and two of them have the methylated form, namely calcium L-methylfolate. Below are five vitamin products; the sixth is gummies with apple cider vinegar, where B9 is a secondary ingredient.

Prices come from the Store API of the shop, as of 2026-08-08, and may change. We calculated the cost per serving as the price divided by the number of daily servings declared by the manufacturer in the product description. All these items fall into the category Supplements.

How to compare the cost per serving and read the label?

The price on the label doesn't tell you much until you break it down to a daily serving. The range in this group of products is over forty-fold: from 15 groszy to nearly seven złoty per day. The chart below illustrates this difference based on data from the Store API.

The chart also shows what the cost per serving does not measure. The most expensive item is collagen with a set of vitamins, in which B9 constitutes a fraction of the formula, so comparing it to a B Complex tablet is comparing two different purchases. It makes sense to compare products with the same purpose.

On the label, look for the chemical form, not the marketing slogan. The entries "L-methylfolate calcium", "5-MTHF" or "(6S)-5-methyltetrahydrofolate" indicate the active form. The word "folate" alone does not determine anything. Also check if the manufacturer provides the amount in micrograms: two out of five products in the table above list vitamin B9 in the composition, but do not declare the content per serving, and without this number, you cannot assess how much of your daily requirement you are covering.

Frequently Asked Questions

What is the difference between folic acid and methylfolate?

Folic acid is a synthetic, oxidized form of vitamin B9 that the body must reduce and methylate before the cell can use it. Methylfolate, or 5-methyltetrahydrofolate, is already an active form and bypasses the step dependent on the MTHFR enzyme. This difference matters for carriers of the MTHFR variant, which reduces the activity of this enzyme.

Who should choose methylfolate instead of folic acid?

Primarily individuals with a confirmed MTHFR variant, especially homozygotes, and those with elevated homocysteine levels. The folate review for Nordic Nutrition Recommendations 2023 states that with MTHFR polymorphism, serum folate levels should exceed 15 nmol/l, compared to the threshold of 10 nmol/l set for the general population.

How much folate should be taken during pregnancy?

The dose is determined by a doctor. Supplements for women planning pregnancy are usually dosed at 400 or 800 µg of vitamin B9 per daily serving. The upper limit of folic acid intake is 1000 µg per day according to EFSA, which also includes pregnant women, so higher doses require medical supervision.

Can folic acid be overdosed?

The upper limit of intake for adults is 1000 µg per day according to EFSA. Masking hematological symptoms of vitamin B12 deficiency has only been described with intakes exceeding 5000 µg per day. Data on other adverse effects of high folic acid intake are described as ambiguous in the NNR 2023 review.

How to check folate levels in the blood?

For adults, the World Health Organization considers a serum folate concentration below 10 nmol/l as a deficiency. For women of childbearing age, a separate indicator is used, namely folate in erythrocytes, with a threshold of 906 nmol/l. Folate status is always assessed together with the concentration of vitamin B12.

Czy gotowanie niszczy folian w warzywach?

Partially yes. Natural folates occur in reduced forms, sensitive to light and oxidation, and are partially destroyed by cooking. The bioavailability of folate from food is estimated to be approximately 50% of the bioavailability of folic acid, with data ranging from 30% to 98%.

If you are looking for a vitamin B9 supplement for yourself, start by comparing forms and daily servings in the category Supplements, as all B group complexes available in the shop are there.

This article is for informational and educational purposes and does not constitute medical advice. Before starting supplementation, consult your doctor, especially if you are taking medications regularly, are pregnant or breastfeeding, or have a chronic illness.

Author: Michał Waluk · Opublikowano: 2026-08-05 · Aktualizacja: 2026-08-08