What The Science Says About 5-MTHF vs Folic Acid | with Angela Hywood

If you or your patients have spent any time on pregnancy forums or Reddit lately, you may have seen comments like:

“Don’t fall for the 5-MTHF hype. Folic acid is the only form proven to reduce neural tube defects.”

I understand why this argument sounds convincing. On the surface it is partly true. But it leaves out important scientific, biochemical and ethical context.

As a fertility naturopath working in reproductive health for more than a decade, and now as the founder of a prenatal supplement company, I want to walk through what the research actually shows, what it cannot show for ethical reasons, and where 5-MTHF genuinely has advantages.

This is not about hype. It is about understanding how folate works in the body.

Why folic acid has “proof” for neural tube defects

Large randomised controlled trials in the late twentieth century showed that folic acid supplementation before and during early pregnancy significantly reduces neural tube defects (NTDs). These findings led to global public health recommendations and food fortification programs.

Because of this evidence, organisations such as: CDC,ACOG,USPSTF, RACGP, RANZCOG recommend 400–800 mcg of folic acid daily prior to conception and during early pregnancy.

So yes — folic acid has strong clinical evidence behind it.

But this is not the full story.

The ethics reason we do not have the same trials for 5-MTHF

Once folic acid was proven to prevent neural tube defects, it became unethical to design studies where pregnant women are deliberately denied an effective intervention.

To prove 5-MTHF reduces neural tube defects using the same type of trial would require:

• One group receiving folic acid
• Another group receiving something not yet proven equivalent

That would knowingly expose pregnancies to preventable risk. Ethics committees will not approve this.

This means that for newer folate forms like 5-MTHF, researchers must rely on:

• biomarker studies
• metabolic research
• reproductive outcomes data

rather than placebo-controlled neural tube defect trials.

This is not a weakness of 5-MTHF. It is a consequence of the success of folic acid.

The biochemical reality often missed in online discussions

Folic acid is not biologically active.

Before it can be used by the body it must be converted through several enzymatic steps into 5-methyltetrahydrofolate (5-MTHF).

5-MTHF is the form that:

• circulates in blood
• crosses the placenta
• participates in DNA synthesis
• supports methylation pathways
• contributes to neural tube development

In other words:

All folic acid must ultimately become 5-MTHF in order to work.

This is established folate metabolism.

Why researchers began studying 5-MTHF

Once this metabolic pathway became clear, scientists asked a logical question:

If 5-MTHF is the biologically active form used by the body, could providing it directly improve folate status more reliably?

Human research comparing folic acid and 5-MTHF shows that 5-MTHF is:

• at least as effective at raising plasma folate
• often more effective at increasing red blood cell (RBC) folate
• effective regardless of MTHFR genotype

RBC folate is particularly important because it is strongly associated with neural tube defect risk.

Population modelling studies show that women achieving RBC folate concentrations above 906 nmol/L have the lowest risk of neural tube defects.

MTHFR and why it matters for some women

The enzyme MTHFR (methylenetetrahydrofolate reductase) plays a key role in converting folate into 5-MTHF.

Certain common genetic variants — especially C677T — reduce enzyme activity.

People with these polymorphisms may have reduced capacity to convert folic acid efficiently.

5-MTHF bypasses this step completely.

Instead of requiring conversion, it delivers folate in the form already used by cells.

RANZCOG reports that approximately:

• 1.5% of people are homozygous for the C677T variant
• around 25% are heterozygous

RANZCOG also notes that the thrombophilic tendency associated with this variant can be minimised with adequate folate, riboflavin, vitamin B6 and vitamin B12.

Fertility, miscarriage and folate metabolism

Folate metabolism plays an important role in reproductive health.

Elevated homocysteine, a marker of impaired methylation, has been associated with:

• recurrent pregnancy loss
• placental complications
• preeclampsia
• foetal growth restriction
• neural tube defects

Approximately one in three women with recurrent miscarriage have elevated homocysteine.

Studies show that 5-MTHF supplementation significantly reduces plasma homocysteine, particularly in individuals with MTHFR polymorphisms.

In one fertility study involving couples with long-standing infertility and recurrent pregnancy loss, many women had previously taken high-dose folic acid without improvement.

When both partners were supplemented with 800 mcg of 5-MTHF (Quatrefolic®):

• 13 spontaneous pregnancies occurred
• 13 additional pregnancies occurred through ART
• the overall ongoing pregnancy rate reached 86.7%

This does not mean folic acid is ineffective. But it does suggest that in certain metabolic contexts, bypassing the folate conversion pathway may improve reproductive outcomes.

The unmetabolised folic acid discussion

High intake of folic acid can result in unmetabolised folic acid (UMFA) circulating in the bloodstream.

This occurs because the enzyme responsible for reducing folic acid (DHFR) has limited activity in humans.

UMFA has been associated in observational studies with:

• altered immune function
• disruption of folate transport
• interference with methylation pathways

The clinical significance of UMFA remains under investigation.

However, 5-MTHF does not contribute to UMFA accumulation because it does not require enzymatic reduction before entering circulation.

So which form should women take?

The most balanced and scientifically accurate answer is this:

Folic acid

• has strong clinical evidence for neural tube defect prevention
• remains the standard public health recommendation
• is safe and effective for many women

5-MTHF

• is the biologically active form used by the body
• bypasses MTHFR-dependent conversion
• raises RBC folate efficiently
• reduces homocysteine
• may provide advantages in some fertility and recurrent miscarriage cases

Choice of folate form should consider individual metabolism, genetics and clinical context, not internet soundbites.

The truth women deserve

Here is the most honest summary of the evidence:

• Folic acid reduces neural tube defects.
• 5-MTHF is the biologically active form responsible for that protection.
• It is unethical to run placebo-controlled neural tube defect trials with 5-MTHF.
• Human studies show 5-MTHF reliably achieves protective folate levels.
• Emerging fertility research suggests benefits in certain populations.

Women deserve more than oversimplified online debates. They deserve science, nuance and personalised care.

If you’re navigating fertility, pregnancy planning, or simply want clarity on which folate form is right for you, let’s work through it together. You can book a consult with Angela here.

Naturopath and Founder of Floralia Wellness & Apothecary, Angela Hywood, has been specialising in women’s health, hormones and fertility for 30 years.

References

1. Bailey LB, Berry RJ. Folic acid supplementation and the occurrence of congenital heart defects, orofacial clefts, multiple births and miscarriage. Am J Clin Nutr. 2005.
2. CDC. Folic Acid: Recommendations. Centers for Disease Control and Prevention.
3. Crider KS, Bailey LB, Berry RJ. Folic acid food fortification—its history, effect, concerns, and future directions. Nutrients. 2011.
4. Hekmatdoost A et al. Methyltetrahydrofolate vs folic acid supplementation in recurrent abortion. J Hum Reprod Sci. 2015.
5. Lamers Y et al. Supplementation with [6S]-5-methyltetrahydrofolate or folic acid equally reduces plasma total homocysteine concentrations in healthy women. Am J Clin Nutr. 2006.
6. Pietrzik K, Bailey L, Shane B. Folic acid and L-5-methyltetrahydrofolate: comparison of clinical pharmacokinetics and pharmacodynamics. Clin Pharmacokinet. 2010.
7. Servy EJ, Menezo YJ. The role of folate in reproductive medicine. Gynecol Obstet Fertil Senol. 2018.
8. Clément A, Menezo Y, Cohen M, Cornet D, Clément P. 5-Methyltetrahydrofolate reduces blood homocysteine significantly in C677T MTHFR carriers consulting for infertility. J Gynecol Obstet Hum Reprod. 2020.
9. RANZCOG. Vitamin and Mineral Supplementation in Pregnancy. Royal Australian and New Zealand College of Obstetricians and Gynaecologists. 2019.
10. Chen P et al. Unmetabolized folic acid in plasma and its implications. Nutrients. 2023.