Folate Metabolism, the Folate Trap, and finding the right therapy for your specific autism

  

Most of the folate and folic acid we eat must be converted into the active form, known as L-methylfolate or 5-MTHF. However, some dietary folate is already in the active form when we eat it and therefore does not rely on MTHFR.

In treating autism, folate metabolism is a key area of therapeutic focus. While folate supplementation seems simple on the surface, the biology behind it is complex — and, if misunderstood, you may even worsen symptoms.

This post explains how folate metabolism works, what the methyl folate trap is, and how different folate and B12 formulations affect outcomes in children and adults with autism, especially those with MTHFR, MTR, or MTRR mutations.

The Normal Folate Cycle 

Folate, a B-vitamin, plays a central role in:

• DNA synthesis 
• Methylation 
• Neurotransmitter production (via SAMe) 

Here is how it works, if you like details:  

• 5,10-methylene-THF helps make thymidine (for DNA).
• Some of this is converted to 5-MTHF by MTHFR.
• 5-MTHF donates a methyl group to homocysteine, converting it to methionine, in a process catalyzed by methionine synthase, which requires vitamin B12.
• This regenerates THF, which goes back into the cycle.

 

The Methyl Folate Trap

 

If there is a vitamin B12 deficiency, or methionine synthase (MTR) dysfunction, the conversion of 5-MTHF → THF is blocked. This causes:

·         5-MTHF to accumulate (it’s “trapped”)

·         THF and 5,10-methylene-THF to fall

·         DNA synthesis to halt

·         Elevated homocysteine, and low SAMe

The result:

·         Anemia

·         Neurological symptoms

·         Behavioral worsening in autism

This is known as the methyl folate trap — and it explains why giving high-dose folate without enough B12 can backfire.

In summary, the methyl folate trap occurs when B12 deficiency or methionine synthase dysfunction prevents 5-MTHF from recycling to THF, stalling DNA synthesis and methylation, even if folate levels are high.

  

Could the Folate Trap Cause Aggressive or Behavioral Regression?

Yes. In autism, worsening behaviors (irritability, aggression etc) after high-dose folinic acid may reflect a relative B12 deficiency or impaired methionine synthase, leading to:

·    Folate trapping

·   Disrupted neurotransmitter synthesis (especially dopamine/serotonin)

·    Low SAMe

In these cases, adding B12 (methylcobalamin or hydroxycobalamin) often improves tolerance to folate therapy and reduces side effects.

 

Other reasons for a possible negative reaction to calcium folinate

Folate metabolism is tightly connected to glutamate and GABA balance.

High folate dosing in some sensitive individuals may cause excess glutamate activity (excitatory), triggering aggression or anxiety-like behaviors.

Children with fragile neurochemical balance may not tolerate sudden shifts in methylation or neurotransmitter levels. A rapid increase in serotonin, dopamine, or norepinephrine can destabilize mood or cause agitation/aggression. This is why you start low and gradually increase your folate supplement.

In such children 5-MTHF may work better, but you still B12.

Apparently, some doctors prescribe antipsychotics to treat agitation caused by calcium folinate; I am not sure that is a good idea.

 

 Choosing the Right Folate: Folinic Acid vs 5-MTHF

	Calcium Folinate / Leucovorin	5-MTHF
Form	Precursor to 5-MTHF	Final active form
Requires MTHFR?	Yes	No
Can enter CSF?	Indirectly	Directly
Behavioral reactions?	More common in some	Usually better tolerated

For whom is 5-MTHF better?

1.      Those with MTHFR mutations (esp. C677T)

2.      Those who react negatively to folinic acid

3.      Those needing direct CNS access

Folinic acid /Leucovorin is converted to 5-MTHF (active folate) through a series of enzymatic steps. First, it is converted into 5,10-methylenetetrahydrofolate, and then the enzyme MTHFR  converts it to 5-MTHF.

In people with MTHFR mutations, this final step may be slower or impaired, meaning folinic acid may not fully convert to active folate. Direct supplementation with 5-MTHF is often preferred in those with these genetic variants.

 

  

The Problem with Synthetic Folic Acid

 Status of mandatory folic acid fortification in 2019

 

In countries like the US folic acid is added to many foods such as flour, bread, pasta and rice in addition to products like breakfast cereals. This is to reduce the incidence of neural tube defects like spina bifida that occur when a fetus lacks sufficient folate in the first 28 days of life.

In Europe there is much less mandatory supplementation of folic acid due to the negative effects. In older people folic acid supplementation can mask vitamin B12 deficiency. High intake of synthetic folic acid can correct the anemia caused by B12 deficiency without correcting the neurological damage. This can lead to delayed diagnosis of B12 deficiency, increasing the risk of irreversible nerve damage, cognitive decline, and dementia in the elderly.

Folic acid is synthetic and must be converted by DHFR (slow, limited in humans).

It competes with both folinic acid and 5-MTHF for cellular entry.

High levels of unmetabolized folic acid can block folate receptors and worsen autism symptoms in some.

Some people with autism should avoid folic acid supplements and fortified foods.

 

The Dilemma: One Size Does not Fit All

While folic acid fortification benefits the general population, especially women of childbearing age, it may pose risks for other groups:

·    Elderly: Risk of masking B12 deficiency

·    Children with autism or FRAA: Risk of blocked folate receptors and behavioral regression

·    Those with MTHFR variants. They have reduced ability to activate folic acid because their ability to convert folic acid into the active form, 5-MTHF, is reduced. This can lead to unmetabolized folic acid (UMFA) in the blood, which may interfere with normal folate metabolism. It can lead to blocking the transport of natural folates into the brain.

 

Here is a study showing that folic acid impairs the transport of active folate (5-MTHF) across the blood brain barrier.

 

Folic acid inhibits 5-methyltetrahydrofolate transport across the blood–cerebrospinal fluid barrier:Clinical biochemical data from two cases

Results: Both patients had low CSF 5MTHF before treatment and high-dose FA therapy did not normalize CSF 5MTHF. There was a dissociation between serum total folate and 5MTHF concentrations during FA therapy, which was considered to be due to the appearance of unmetabolized FA. The addition of folinic acid did not improve low CSF 5MTHF in the KSS patient and the cessation of FA resulted in the normalization of CSF 5MTHF. In the patient homozygous for MTHFR C677T, minimization of the FA dosage resulted in the normalization of CSF 5MTHF and an increased CSF-to-serum 5MTHF ratio.

Conclusions: Our data suggest that excess supplementation of FA impaired 5MTHF transport across the blood-CSF barrier. In the treatment of CFD, supplementation of folinic acid or 5MTHF (in cases of impaired 5MTHF synthesis) is preferred over the use of FA. The reference values of CSF 5MTHF concentration based on 600 pediatric cases were also provided.

  

B12 - Forms and why it matters

To prevent the folate trap, adequate B12 is critical.

                          

Methylcobalamin        Active, supports methylation directly

Hydroxycobalamin      Longer-lasting, converted to methyl- or adeno-B12

Adenosylcobalamin     Active in mitochondria

Cyanocobalamin         Synthetic, less ideal, may not work in autism

 

Methylcobalamin or hydroxycobalamin are best for autism and CFD.

 

Can it be oral?

Yes, but high doses needed (1–5 mg daily)

Subcutaneous injections may be better absorbed in some

 

What About Betaine / TMG?

Betaine (trimethylglycine) provides methyl groups to convert homocysteine to methionine via the BHMT pathway (mostly in the liver, not brain).

Useful if:

·         Homocysteine is high

·         B12 metabolism is impaired

·         Need extra methylation support

 But, it does not bypass the folate trap in the brain — you still need functional methionine synthase and B12.

 

When Do You Need More SAMe?

SAMe (S-adenosylmethionine) is the body’s master methyl donor, essential for: 

·         Neurotransmitter synthesis

·         Myelination

·         Detox pathways

 

You may need extra SAMe if:

·         You have low methionine/SAMe

·         There is fatigue, depression, or tics

·         Homocysteine is high despite folate + B12

Oral SAMe is poorly absorbed unless enteric-coated.

Do not assume “more folate = better” without addressing B12

 

Conclusion

Whether a person with autism stands to benefit from tuning up their folate metabolism will depend on their unique situation. Many people need no intervention at all.

For others it is highly beneficial to customise an intervention plan. It would include some, or all, of the following. 

·   Reduce expose to synthetic folic acid used to fortify flour, pasta, bread, rice, breakfast cereals etc.

·   Supplement with 5-MTHF or calcium folinate / Leucovorin

·   Supplement vitamin B12, in the form of methylcobalamin or hydroxycobalamin

·    Supplement Betaine/TMG

·    Supplement SAM

     ·  Consider supplementing PQQ if positive for FRAA 

 

The only substance that is prescription-only is calcium folinate / Leucovorin. It looks like 5-MTHF is actually the better choice for most people and it is much more accessible.

We have seen that the potency of generic calcium folinate / Leucovorin is highly variable, possibly due to different excipients that are added. How reliable the OTC 5-MTHF supplements are is an open question.

If you find this subject confusing, use ChatGPT to help you. You can even upload a screenshot of your MTHFR/MTR/MTRR mutations and then get tailored advice. It is free !!  (for now)

 

If you are someone who likes lab tests, the options include: 

• Folate receptor antibodies (FRAA) – to check for blocking autoantibodies www.fratnow.com
• Serum and CSF 5-MTHF – to detect cerebral folate deficiency
• Homocysteine – elevated if methylation is impaired
• MMA (methylmalonic acid) – elevated in B12 deficiency
• Vitamin B12 – ideally with active B12
• Genetic testing – particularly MTHFR, MTR, and MTRR variants to assess methylation capacity

High MMA = likely B12 deficiency, even if serum B12 is "normal".

This is especially important in people with neurological symptoms or MTHFR-related metabolism issues.

 

Measuring serum (blood) 5-MTHF provides insight into how much active folate is circulating in the body. This helps detect:

• Folate trap from B12 deficiency (high folate, low methylation)
• Impaired folate metabolism in MTHFR or MTR/MTRR variants
• Folate absorption or transport problems, especially if CSF 5-MTHF is also tested
  It’s particularly useful when deciding whether folinic acid, 5-MTHF, or B12 supplementation is effective or needed.

CSF 5-MTHF (cerebrospinal fluid via lumbar puncture) gives a direct measure of active folate availability inside the brain. This is important because:

• Some children with autism or FRAA (folate receptor autoantibodies) have low CSF 5-MTHF even with normal blood folate. Some have FRAA and normal CSF 5-MTHF
• High serum folic acid can block transport of 5-MTHF into the brain, lowering CSF levels.
• It can help diagnose Cerebral Folate Deficiency (CFD), especially if symptoms improve with folinic acid.

Low CSF 5-MTHF with normal serum levels suggests a transport problem, not a folate intake issue.

PQQ as a Folate Transport Enhancer

A supplement called Pyrroloquinoline quinone (PQQ) may help bypass folate receptor autoantibody (FRAA) blockage by upregulating alternative folate transporters (RFC and PCFT) in the brain. This could improve delivery of both calcium folinate (leucovorin) and 5-MTHF into the brain when folate receptor alpha (FRα) is blocked.

Human data is lacking; all evidence from animal/cell studies. Some people report adverse effects (e.g. fatigue, overactivation)

For individuals with FRAA, PQQ might enhance the effectiveness of folinic acid or 5-MTHF by improving alternative transport into the brain.

Cerebral Folate Deficiency – increasing cerebral folate without increasing plasma/blood folate, via activating the reduced folate carrier (RFC)

 

Source: https://autism.fratnow.com/blog/folate-transport-systems-i-transmembrane-carriers/

Two readers of this blog have been telling me about the fundamental role of brain energy and metabolism in autism. Marco sent me a book called Brain Energy by a psychiatrist at the Harvard Medical School. He stumbled upon this subject when he encouraged a patient to lose weight using the ketogenic diet. As well as losing weight, the patient’s decades-long psychiatric disorders seemed to vanish. The author, Dr Palmer, now believes that many of his patients actually have metabolic disorders as the underlying basis of their psychiatric symptoms. 

Our reader Natasa is approaching with a similar idea, essentially that autism features a brain running on empty.

Today’s post is about increasing the level of folate within the brain, by targeting similar metabolic pathways to those that will boost “brain energy.”

Low levels of folate within the brain will cause varying degrees of neurological disorder.

There are three ways folate can cross into the brain.

1.     Folate receptor alpha (FRA)

2.     Proton-coupled folate transporter (PCFT)

3.     Reduced folate carrier (RFC)

Autoantibodies to the FRA have been linked to neurodevelopmental diseases, particularly cerebral folate deficiency, schizophrenia and autism. Recent studies have shown that these neurodevelopmental disorders can be treated with folinic acid (leucovorin).

Dr Frye, Professor Ramaekers and others are targeting the problem of low folate in the brain by supercharging the level of folate in the bloodstream and hoping more squeezes through the blood brain barrier.

In my previous post I mentioned that Agnieszka has pointed out the idea of using the supplement PQQ. This targets the third transport mechanism above, it is aiming to get more folate across via  the Reduced Folate Carrier (RFC).

Somebody recently wrote their PhD thesis on exactly this topic:- 

Regulation of Folate Transport at the Blood-Brain Barrier: A Novel Strategy for the Treatment of Childhood Neurological Disorders Associated with Cerebral Folate Deficiency

Camille Alam, Department of Pharmaceutical Sciences, University of Toronto 

Additionally, we provided in vitro and in vivo evidence that RFC expression and transport activity is inducible by another transcription factor, NRF-1. These findings demonstrate that augmenting RFC functional expression through interaction with specific transcription factors could constitute a novel strategy for enhancing brain folate delivery. Modulating folate uptake at the BBB may have clinical significance due to the lack of established optimal therapy for neurometabolic disorders caused by loss of FRα or PCFT function. 

What Camille is saying is that if folate transport mechanism number 1 and/or number 2 are not working, we can reinvigorate mechanism number 3.

So if you have Dr Frye’s folate receptor antibodies, or PCFT isn’t working then you might focus on Reduced Folate Carrier (RFC).

The good news is that we have lots of ways to target Reduced Folate Carrier (RFC).

We do not, it seems, have any clever ways to target PCFT. 

NRF-1 and PGC1-alpha

There is a lot in this blog about PGC1-alpha, because it is the master regulator for biogenesis of mitochondria.

All those people with impaired “brain energy” would love to activate PGC1-alpha.

NRF-1 is an activator of mitochondrial respiratory chain genes. NRF-1 specifically targets genes encoding subunits of the mitochondrial respiratory chain complexes, particularly complexes I, III, and IV. By binding to their promoters, NRF-1 directly stimulates their transcription, leading to increased synthesis of these critical protein components and enhanced oxidative phosphorylation (OXPHOS) capacity.

Synergy between NRF-1 and PGC-1alpha

PGC-1alpha acts as the upstream regulator. Various stimuli, such as exercise, cold exposure, and certain hormones, can trigger PGC-1alpha expression. Once activated, PGC-1alpha directly interacts with and co-activates NRF-1, enhancing its binding to target gene promoters and amplifying its transcriptional activity.

NRF-1 as the downstream effector.  NRF-1 fine-tunes the expression of specific mitochondrial genes, ensuring a balanced and efficient OXPHOS system. This synergy between PGC-1alpha and NRF-1 optimizes mitochondrial function and cellular energy production.

So for Natasa, trying to boost energy production in the brain and in the rest of the body, it would be ideal to have more NRF-1 and more PGC-1alpha

What has optimized mitochondrial function got to do with more folate in the brain?

It turns out that you can increase expression of Reduced Folate Carrier (RFC) via activating NRF-1 and/or PGC1alpha.

So what is good for your brain energy is likely to also be good for your brain folate.

Nuclear respiratory factor 1 (NRF-1) upregulates the expression and function of reduced folate carrier (RFC) at the blood-brain barrier

Folates are important for neurodevelopment and cognitive function. Folate transport across biological membranes is mediated by three major pathways: folate receptor alpha (FRα), proton-coupled folate transporter (PCFT), and reduced folate carrier (RFC). Brain folate transport primarily occurs at the choroid plexus through FRα and PCFT; inactivation of these transport systems results in suboptimal folate levels in the cerebrospinal fluid (CSF) causing childhood neurological disorders. Our group has reported that upregulation of RFC at the blood-brain barrier (BBB) through interactions with specific transcription factors, that is, vitamin D receptor (VDR) could increase brain folate delivery. This study investigates the role of nuclear respiratory factor 1 (NRF-1) in the regulation of RFC at the BBB. Activation of NRF-1/PGC-1α signaling through treatment with its specific ligand, pyrroloquinoline quinone (PQQ), significantly induced RFC expression and transport activity in hCMEC/D3 cells. In contrast, transfection with NRF-1 or PGC-1α targeting siRNA downregulated RFC functional expression in the same cell system. Applying chromatin immunoprecipitation (ChIP) assay, we further demonstrated that PQQ treatment increased NRF-1 binding to putative NRF-1 binding sites within the SLC19A1 promoter, which encodes for RFC. Additionally, in vivo treatment of wild type mice with PQQ-induced RFC expression in isolated mouse brain capillaries. Together, these findings demonstrate that NRF-1/PGC-1α activation by PQQ upregulates RFC functional expression at the BBB and could potentially enhance brain folate uptake.

The hugely simple intervention mentioned above is to just take vitamin D. This has nothing to do with brain energy.

Upregulation of reduced folate carrier by vitamin D enhances brain folate uptake in mice lacking folate receptor alpha

Folates are critical for brain development and function. Abnormalities in brain folate transport have been implicated in a number of childhood neurodevelopmental disorders, including cerebral folate deficiency syndrome, hereditary folate malabsorption, and autism spectrum disorders. These disorders have devastating effects in young children, and current therapeutic approaches are not sufficiently effective. In this study, we demonstrate that functional expression of the folate transporter, reduced folate carrier, at the blood–brain barrier and its upregulation by the vitamin D nuclear receptor can remarkably increase folate transport to the brain. These findings provide a strategy for enhancing brain folate delivery for the treatment of neurometabolic disorders caused by folate transport defects.

 Low vitamin D correlates with poor health, dementia, and death from all causes

Taking vitamin D has become popular in recent years.

A correlation does not guarantee causality.  It was thought that vitamin D might be the silver bullet to improved health in older people. It has not proved to be.

Low vitamin D also correlates with less time outdoors, doing some physical activity. Taking vitamin D does not mean you will live longer, but we know for sure that exercise improves many medical concerns that will improve healthy life expectancy.

The concern many people now have regarding skin cancer leads to some healthy active people having low vitamin D. Put on that sunscreen and your exposed skin will not be able to produce your vitamin D.

Vitamin D is important to health and is easy to maintain in the normal range, but it is just one element of good health. It might be one way to increase folate in the brain, for those who need it. 

 

Conclusion

How do you increase folate in the brain?

The obvious way is to put more folate in your blood, this is the standard therapy. You either take calcium folinate tablets or, very rarely, the more potent infusions.

If you have antibodies blocking transport via FRA, you could follow the hypothesis that these antibodies are from a reaction to cow’s milk and try going dairy-free. There is a complex relationship between milk and folate receptor alpha antibodies (FRAA), but direct evidence of milk causing FRAA production is limited.

Milk, particularly cow's milk, contains proteins similar to folate receptor alpha found in humans. Some individuals, mainly those with a genetic predisposition, could develop FRAA that cross-react with these milk proteins. This cross-reactivity would not necessarily mean the milk directly caused FRAA production but might trigger an existing immune response. Some studies, though not all, have found an association between higher milk consumption and increased FRAA levels.

If you want to increase folate transport via our third mechanism, Reduced Folate Carrier (RFC) you have many options:

The obvious first step is to take a vitamin D supplement to raise levels to the high end of normal. This can be done by taking a larger supplement just once a week, because vitamin D has a long half-life.

As you can see from the study below in children there is a correlation between low vitamin D and low folate in children.

 

Evaluation of correlation between vitamin D with vitamin B₁₂ and folate in children

The present study reported a positive correlation between vitamin D and vitamin B12 and folate levels. Regular measurement of these two micronutrient levels in children with vitamin D deficiency is important for public health.

Vitamin D is low in much of the population, even more so in wintertime. It seems particularly low in children with autism, perhaps because they are spending less time playing outside than other children.

Activate NRF-1 and/or PGC1alpha:

1.     Exercise, particularly endurance training

2.     PQQ supplement

3.     Perhaps resveratrol/pterostilbene

4.     Butyric acid / sodium butyrate

5.     The very safe old drug Metformin

6.     Other type 2 diabetes drugs like Pioglitazone

Metformin has been shown to raise IQ in Fragile-X by about 10 points and has a range of metabolic benefits and even cancer preventative effects. This common diabetes medication primarily targets AMPK, an energy sensor molecule upstream of PGC-1alpha. By activating AMPK, metformin indirectly stimulates PGC-1alpha and subsequently NRF1, leading to enhanced mitochondrial function.

Pioglitazone has been researched in autism and is my choice for peak risk spring/summer aggression and self-injury. Pioglitazone can potentially upregulate PGC-1alpha expression through several pathways:

•                    Pioglitazone activates AMPK, an important energy sensor molecule. AMPK can then stimulate PGC-1alpha expression through various signaling pathways.

•                    Pioglitazone activates PPAR-gamma and PPAR-gamma directly interacts with PGC-1alpha, potentially increasing its activity.

I think Metformin has a better safety profile than Pioglitazone and so better for every day use.

Butyric acid does have the potential to activate PGC-1alpha. Butyric acid is produced in the gut by fermentation. You need “good” bacteria and fiber. People with healthy diet naturally produce it. You can also buy it as a supplement (sodium butyrate) since it has numerous benefits – everything from gut health, bone health to a tight blood brain barrier.

According to a doctor I was talking to recently, nobody wants to hear that exercise is a key part of health. It is free and the side effects are generally all good ones. Endurance exercise will boost NRF1 and PGC1alpha. Many people with autism are overweight, often due to the psychiatric drugs they have been put on.

Sirtuin activators boost NRF1 and PGC1 alpha. There are drugs and foods which can do this, but a potent way is through exercise.

I hope Dr Frye is checking his patients’ vitamin D levels and supplementing to the safe upper limit.

Those taking I/V calcium folinate might want to look at the more potent ways to activate NRF1 and/or PGC1alpha.