The many different types of L-methylfolate: how to choose the right methylfolate for you

Which folate or methylfolate supplement is best?

Good question!

Choosing the right dietary supplement is now more difficult than ever. A saturated market along with overblown marketing campaigns can blur our understanding of what’s good and what’s not. 

Brands will often use unfamiliar jargon and visual effects to “sell” their products, ultimately confusing the consumer. Too often, this strategy is about gaining credibility through alluring claims in the hope that consumers won’t feel compelled to compare products.

Well, we’re about to clear things up once and for all by explaining exactly what makes a methylfolate supplement good, and how to choose the best. 

At Methyl-Life®, we believe in helping our customers understand exactly what’s best for their health. This detailed resource will explain and compare the industry-leading methylfolate nutrients competing on the market today.

Folate - also known as vitamin B9 - is a nutrient required for numerous processes in the body. It’s found naturally in foods such as legumes, nuts, and leafy green vegetables.

Folic acid is the synthetic form of folate that is most commonly included in supplements, including multivitamins, B complex vitamins, and prenatal supplements. This is because folic acid is a much cheaper option than natural, active folates. 

However, folic acid cannot be used directly by the body. It must undergo a four-step conversion process that requires the dihydrofolate and methylenetetrahydrofolate reductase enzymes (DHFR and MTHFR)¹ which our genes are required to derive for us. 

Unfortunately, around 40-50% of the population have a mutation of the MTHFR gene, which means their body is unable to properly convert folic acid into its active form.² For these people, a folic acid supplement is of no benefit, and may result in their accumulating high levels of unmetabolized folic acid (UMFA) in the body.³ UMFA Syndrome is associated with a range of metabolic, cognitive, and hypersensitivity health issues.⁴

For those with MTHFR mutations, the best way of obtaining folate is with L-methylfolate. 

L-methylfolate is the natural and highly bioavailable form of folate. It is the predominant form used by the body for its many biological processes. As it is already metabolized, it can bypass the MTHFR mutation for immediate use in the body.⁵

Unlike folic acid, L-methylfolate can cross the blood-brain barrier for immediate uptake in the body. It also does not mask pernicious anemia, which can occur when folic acid allows normal pyrimidine synthesis to progress, making underlying vitamin B12 deficiency undetectable.⁶

L-methylfolate is the pure form of the naturally-occurring predominant form of folate. As an essential water-soluble B-vitamin, methylfolate plays a key role in numerous metabolic pathways, including cell division and repair.⁷

Supplementation with methylfolate during pregnancy is preferred over folic acid for its ability to bypass the MTHFR genetic mutation. Folate is also shown to be more effective than folic acid for infertility and fetal brain development, and does not carry the risk of unmetabolized folic acid syndrome (UMFA).⁸ 

Different types of methylfolate may be used in different products. Each type can vary in terms of its structure, which can then affect its delivery and uptake in the body.

The majority of all L-methylfolates on the market are bound to one of two major salt molecules: calcium salt or glucosamine salt. The salt molecule has a lot to do with how much “free methylfolate” can be delivered to the body. Some methylfolates have a crystalline molecular salt structure and others an amorphous salt structure. This molecular structure correlates directly to a methylfolate’s stability and therefore also its purity and potency. Methylfolates with a crystalline molecule structure are more potent and pure and remain so for longer due to their stable structure.

Fully active, bioidentical methylfolate is chemically represented as L or 6S. The inactive type of methylfolate is referred to as D or 6R. A combination of active and inactive methylfolate is referred to as ‘racemate’ or a ‘racemic form’ and represented as DL- or 6S/6R-.

There are several different types of L-methylfolate on the market which can vary somewhat in terms of their quality and effectiveness.

Factors that differentiate methylfolate supplements include:

• The chemical isomer structure: Is L or (6S) best? What about (6S)+(6R) or DL?
• The type of salt that the active L or (6S) methylfolate isomer is bound to (i.e. calcium, glucosamine, magnesium, etc.)
• The crystalline or amorphous molecular structure type of the methylfolate will determine its stability and potency
• The purity which should measure all of the similar folate compounds that are NOT L-5-MTHF

Cerebrofolate™ is superior to other L-methylfolates for many reasons.

Cerebrofolate™ is a crystalline (Type I) calcium salt form of (6S)-5-methyltetrahydrofolate (or L-5-MTHF).  Most clinical studies on methylfolate so far have used a bioidentical crystalline form, Type I calcium salt structured methylfolate.

Cerebrofolate™ has a molecular weight of 497.5g/mol, which facilitates its transfer through intestinal cells. L-5-MTHF glucosamine is almost twice as heavy at 817.8g/mol, which can slow down the transfer.

Cerebrofolate™ comprises 80% “free methylfolate”, while L-5-MTHF glucosamine comprises only ~52% “free methylfolate”. This makes Cerebrofolate™ the most potent L-methylfolate on the market today. Ingesting just 1 mg of the raw ingredient provides 0.80 mg of absorbable L-methylfolate.

Cerebrofolate™ is produced in a cGMP facility which is FDA registered and audited, FSSC22000, Kosher, Halal and ISO9001 certified. FSSC22000 represents the highest level of quality and certification for ingredients used in dietary supplements. While most companies employ skip-batch testing (testing once every determined number of batches), every single batch of Cerebrofolate™ is tested for impurities and heavy metals.

Cerebrofolate™ has been shown to retain its stability for up to two years when stored at room temperature.

A 2023 study¹¹ that compared brands Metafolin®, Quatrefolic®, and Cerebrofolate™ found that Cerebrofolate™ and Metafolin® exhibited superior stability and potency in comparison to amorphous salt and glucosamine salt forms of methylfolate. In addition, Cerebrofolate™ showed the least amount of change in the physical appearance and total impurities compared to other brands, as well as higher amounts of free folate levels, indicating greater potency.

One open-air comparison study by Jinkang Pharmaceutical¹² found that amorphous glucosamine salt L-methylfolate lost 35.2% potency within 60 days. It also generated an impure compound that made up 19.9% of the total mass.

Over the same period, an L-5-MTHF calcium product lost only 0.55% of its potency and contained only 0.27% impure compounds.

The USP standard and limit for impurities in methylfolate is 2.5%. Cerebrofolate™ exceeds that standard by 3x as it contains 0.8% impurities. This makes Cerebrofolate™ one of the purest forms of methylfolate available.

Methyl-Life® is the first company in the world to provide an L-methylfolate product line using Cerebrofolate™.

• Leucovorin Calcium
• Calcium folinate
• Folic acid (a synthetic form of folate often used in supplements and fortified foods)
• Folinic acid
• (6R)-5-methyltetrahydrofolate
• (6R)-5-MTHF

Both the natural L-isomer and the inactive D-isomer of 5-MTHF have two chiral centers. However, both chiral centers in L-MTHF have the natural L-configuration (6S, αS), whereas in the D-isomer (D-5-MTHF) the configuration of the chiral carbons is the inactive (6R, αS). Chemically speaking, the L/(6S) and D/(6R) isomers are mirrors of one another.

One is usually considered the “active” ingredient in a compound and the other is often considered “inactive”, "unnatural" or a “contaminant”.

The (6S, αS) isomer of calcium L‐methylfolate corresponds to the natural form of folate. This simply means that the (6S, αS) isomer is considered the pure form the body can use.

Any form of methylfolate that does not specify the L isomer form (or (6S) isomer form) of methylfolate may not be 99% pure biologically active methylfolate.

Folates degrade under light, heat, oxygen, moisture, and acidic pH, which is why stability is so important.

The purity of an ingredient refers to the percentage made up of only the 6S or L-isomer. In a pure L-methylfolate such as Cerebrofolate™, 98-99% of the ingredient is made up of the calcium salt molecule that the (6S) isomer of 5-MTHF is bound to. This means it contains less of the 6R or D inactive isomer content in the raw ingredient.

When you ingest a product that is said to be ~98-99% pure L-Methylfolate, after the calcium salt, water and impurities all dissolve, 80% of the total raw ingredient amount (for Cerebrofolate™) is actually the active (6S) or L-isomer of 5-MTHF that’s available for the body to absorb.

This is referred to as the “free methylfolate” percentage of a nutrient. During ingestion, methylfolate becomes available for use in the body through a process called “first-pass metabolism” or “first-pass absorption.”

Cerebrofolate™ has been tested and confirmed to have the highest potency percentage of any other methylfolate on the market.

• Folic acid
• D forms and (6R) forms of methylfolate are exactly the same (these are less biologically active and are referred to as D-5-MTHF or D-5-Methyltetrahydrofolate, (6R)-5-MTHF, (6R)-5-Methyltetrahydrofolate).  This is a cheap form that can be substituted in lower quality products.
• 5-Methyltetrahydrofolate - if labeled this way a product can contain the D/6R isomer form of methylfolate which would actually be considered a “contaminant” in a pure active L-methylfolate.

These forms will contain more than 1% of the D or (6R) isomer form of methylfolate.

Quatrefolic® is the amorphous glucosamine salt form of L-methylfolate with a limited stability. This simply means it loses its potency faster than a crystalline-structured type would. Studies have suggested this form has a higher bioavailability than the calcium salts of L-methylfolate. 

However, it requires almost twice the dosage amount of calcium salt forms because glucosamine is heavier than calcium. The specific form of this L-methylfolate is covered by a patent.

The main difference between Quatrefolic® and the calcium salt-based L-methylfolate forms is that the (6S)/L isomer of 5-MTHF is bound to a glucosamine salt molecule. This is often labeled as (6S)-5-Methylfolate, glucosamine salt.

Quatrefolic® is also ~98-99% pure, which means that 98-99% of the 5-MTHF ingredient is made up of the (6S)/L isomer tied to the glucosamine salt molecule.

When ingested, however, the glucosamine salt molecule and other non-L-methylfolate parts dissolve and the first-pass absorption rate is closer to 49-52%. This means about 50% of the raw ingredient becomes available for the body to use.

Quatrefolic® is often marketed as “the most bioavailable L-methylfolate”. This simply means it becomes available in the bloodstream faster for the body to absorb. In other words, the glucosamine salt molecule dissolves and metabolizes faster in the body than the calcium salt molecule. However, faster is not necessarily better in the case of methylfolate metabolism.

The first generation of the ingredient L-methyltetrahydrofolate (L-methylfolate) was first patented and trademarked by Merck as Metafolin®. Metafolin® was FDA-notified and released as a prescription “medical food” in 2001. It is the main component in many “medical foods” today:

• Deplin® - an adjunct antidepressant prescription for treatment-resistant depression 
• Neevo® - a prenatal prescription for pregnancy  
• Metanx® - a diabetic neuropathy prescription
• Cerefolin® - a dementia/Alzheimer’s prescription

Metafolin® is a calcium salt form of L-methylfolate. Metafolin® is a patented (Type I) crystalline and stable form of the “L” isomer of a specific type of calcium salt. Merck’s patent on Metafolin® has expired.

A crystalline salt form is a key requirement for satisfactory stability in capsules or tablets, so Metafolin® is less likely to lose its potency over time. The crystalline salt form is preferable so that its properties remain constant during pharmaceutical handling, transportation, and use¹³.

While Cerebrofolate™, a newer generation methylfolate, is biochemically identical to Metafolin®, it’s worth noting that Cerebrofolate™ has been tested as more pure and more potent.

Extrafolate S® is another type of calcium salt methylfolate. Extrafolate-S® is typically labeled as (6S)-5-methyltetrahydrofolate.

Extrafolate-S® is an amorphous calcium-salt form which is much less stable and tends to lose potency over time. It is L-isomer only, so its purity is around ~98-99%. It also has a similar first-pass absorption loss rate as Metafolin®, making it about 72-74% absorbable.

This means that 1 mg of Extrafolate-S® equals approximately 0.74 mg of the active L-methylfolate (bioactive “free methylfolate”) that can be absorbed by your body.

However, an amorphous ingredient can lose up to 16% of its potency over 12 months while a crystalline molecule form will only lose 1-2%.

Cerebrofolate™ methylfolate is a crystalline salt form of L-5-MTHF Calcium. A crystalline salt molecule is more stable which means that it is not as likely to lose potency over time¹⁴.

Like the other patented L-methylfolates, Magnafolate® is a ~98-99% pure form of L-methylfolate (only the (6S)/L isomer in the ingredient). It is also a calcium salt-based crystalline form and is extremely stable.

Magnafolate® has a ~78% “free methylfolate” absorption rate. This means that 1 mg of raw Magnafolate® equals approximately 0.78 mg of the active L-methylfolate (bioactive “free methylfolate”) that can be absorbed by your body.

Magnafolate® is similar to Metafolin®, it is also a calcium salt form, has the pure (6S) isomer, and its methylfolate type is a crystalline structure (Type C) for stability. The Type C crystallinity is patent-protected. Magnafolate® has no human clinical studies behind it.

Leucovorin is a folic acid analog, which means it is similar to folic acid. It is used to treat megaloblastic anemia, and the toxic effects of methotrexate. It is also given with Fluorouracil to enhance the effects of chemotherapy when treating cancers of the digestive system, or to reduce its side effects.

Leucovorin has also been recently trialed with an Autism Speaks study group.

When comparing products, look for a CofA (Certificate of Analysis) detailing the exact amount of the 6R or D-isomer (as tested) in their methylfolate. This should be considered an ‘impurity’ and should show up as less than 0.15%. In the CofA for Cerebrofolate™, this value is reported in our test results as undetectable.

Note: FDA labeling regulations

Supplement manufacturers are prohibited from making false claims about their products and from selling products that are adulterated or misbranded. Brands themselves are responsible for ensuring that their products are safe and correctly labeled before marketing so that they meet all FDA requirements.

However, changes to FDA requirements may be implemented by different brands at different stages. This could mean that at any given time, different methylfolate products vary significantly in terms of their contents -  but their labels may indicate to consumers that they contain the same ingredients.

DFE - Dietary Folate Equivalent

From 2020-2021, the FDA implemented new regulations regarding the DFE (dietary folate equivalent) on supplement labels. DFE are the units that account for the differences in the absorption of folate obtained from dietary supplements vs. food sources.

The FDA has determined that food folate is 50% bioavailable and that synthetic folic acid used in dietary supplements and fortified foods is 85% bioavailable.  The math here gives us a 1.7x multiple (50% divided by 85% gives you 1.7).

In other words, the FDA now requires that all “folate nutrients” are to be multiplied by 1.7 in order to show their “dietary folate equivalent” or basically their food folate comparison amount. Essentially it’s comparing the amount of folate you would get from taking the vitamin ingredient vs. the “folate equivalent” you would get from eating a plate of folate-rich food, like spinach. The percentage of folate found in food is lower than it is in folate nutrients like folic acid or methylfolate.

If one serving contains 1,000 mcg of folate, the product must now be labeled as 1,700 mcg folate DFE (1,000 mcg x 1.7 = 1,700 mcg). Check out our YouTube video to learn more about DFE.

So, a product previously labeled as providing 1,000 mcg of folate now must be labeled as 1,700 mcg DFE. On the other hand, a product previously labeled as providing 1,000 mcg that now shows 1,000 mcg DFE may have reduced the amount of folate from 1,000 mcg of ingredient down to ~590 mcg of ingredient.

Methyl-Life® formulas have not changed at all. Our products still carry the exact same amount of methylfolate that they always have, but the new DFE labeling on our products may suggest that amounts are much higher.  

Crystalline salt molecules are considered extremely stable due to their regular structure, lower energy state, efficient packing, and long-range order.

Amorphous salt molecules are known to be much less stable due to a more disordered atomic arrangement, resulting in higher energy states, greater potential for atomic movement, and higher exposure to oxygen. Chemical degradation can also affect high-energy amorphous molecules¹⁰.

The form type of a methylfolate salt molecule is the main difference between leading brands of methylfolate. The concern with taking supplements of lower stability is that they degrade more quickly, which can lead to potentially harmful constituents.