The Paradoxical Choice: 5 Reasons We Recommend Folic Acid Over 5-MTHF for Long-term Healthy Blood Flow Support
Truth Full HealthWhy “More Bioavailable” Does Not Automatically Mean More Appropriate
Earlier – we discussed the potential value —and important limitations—of choosing vitamin and supplement ingredients marketed as “more bioavailable.”
We also briefly explained why we consider folic acid a more appropriate folate ingredient than alternatives marketed as “more bioavailable” in the context of heart and metabolic health support.
In this post, we take a closer look at five reasons behind that decision by comparing two commonly used forms of folate: folic acid and 5-MTHF.*
*5-MTHF—short for 5-methyltetrahydrofolate and also called l-methylfolate—is a form of folate commonly marketed as being more readily available for the body to use than folic acid.
Reason 1: Better Immediate Absorption Does Not Necessarily Mean Better Absorption Over Time
|
Myth |
Reality |
|
5-MTHF is absorbed better than folic acid, especially by people with common MTHFR gene variants. |
Studies suggest that 5-MTHF may produce a slightly faster or greater initial rise in blood folate, but this difference balances out within hours to days, resulting in similar overall bioavailability to folic acid.[1],[2] |
People with common MTHFR gene variants can still process folic acid.
The Centers for Disease Control and Prevention (CDC) states that folic acid intake is generally more important than MTHFR genotype in determining blood folate levels.[3]
Reason 2: Unclear How Many DFEs 5-MTHF Actually Provides
How do we know whether we are getting enough folate?
We need a standardized unit that allows us to compare folate intake from different sources.
For example, when we drink a protein shake and look at the Nutrition Facts label, the product shows how many grams of protein it provides.
Grams are the standardized unit in this example.
For folate intake, the U.S. Food and Drug Administration (FDA) uses a standardized unit called Dietary Folate Equivalents, or DFE.
This means that folate intake from different sources—including food, fortified foods, vitamins, and supplements—can be reported in DFE.
The problem is that the conversion between 5-MTHF and DFE has not been formally established.[4]
This creates two practical concerns:
- Risk of consuming too much folate.[5]
- Risk of paying more without receiving a proven additional benefit, as 5-MTHF supplements are often more expensive.
Reason 3: 5-MTHF Labels Commonly Use the Same DFE Conversion as Folic Acid
Let’s look at some real-life examples of how many DFE units 5-MTHF and folic acid vitamins provide.
5-MTHF example 1.
How much 5-MTHF per serving? 5 mg, or 5,000 mcg.
How many DFEs per serving? 8.3 mg, or 8,333 mcg.
This means that every 1 mg of 5-MTHF is reported as equivalent to 1.667 mg DFE.
Does the label differentiate between people with and without common MTHFR gene variants? No
5-MTHF example 2.
How much 5-MTHF per serving? 1 mg, or 1,000 mcg.
How many DFEs per serving? 1.667 mg, or 1,667 mcg.
This means that every 1 mg of 5-MTHF is reported as equivalent to 1.667mg DFE.
Does the label differentiate between people with and without common MTHFR gene variants? No
Folic acid example.
How much folic acid per serving? 0.8 mg, or 800 mcg.
How many DFEs per serving? 1.333 mg, or 1,333 mcg.
This means that every 1 mg of folic acid is reported as equivalent to 1.667mg DFE.
Comparing the DFE conversions for 5-MTHF and folic acid
As shown above, these labels use essentially the same conversion factor for 5-MTHF and folic acid.
This reflects the lack of sufficient evidence to support assigning 5-MTHF a higher DFE conversion factor than folic acid.
Manufacturers commonly use this conversion to follow FDA’s labeling guidance, as explained in more detail below.
Reason 4: FDA Labeling Guideline Does Not Assign 5-MTHF a Higher DFE Conversion Than Folic Acid[6]
In its official guideline, FDA states that other than folic acid, manufactured forms of folate—such as calcium or glucosamine salts of 5-MTHF—may be added to vitamins or supplements.
FDA allows a manufacturer to use its own properly established conversion factor, provided that the label is truthful and not misleading.
However, FDA states that it would not expect a conversion factor for any manufactured form of folate to exceed 1.7, which is comparable to folic acid.
In practical terms, FDA does not expect 5-MTHF to be declared as providing more DFE than folic acid.
Reason 5: The Weight of Long-Term Evidence Is Heavily Skewed in Favor of Folic Acid Over 5-MTHF
As discussed in our earlier post, decades of high-quality human research have repeatedly suggested that folic acid may help support long-term healthy blood circulation.
By comparison, very limited long-term human research is available for 5-MTHF in this area.
One high-quality human study showed that 5-MTHF in combination with B vitamins (the “5-MTHF group”) may support long-term healthy blood flow.[7] However, the 5-MTHF group also appeared to live shorter compared to the placebo group.
The CDC also strikes a cautious note regarding the limited evidence for 5-MTHF relative to folic acid.[8]
Wrapping It Up
Although 5-MTHF may have slightly higher bioavailability at the very start of supplementation, there is no strong evidence that it provides a meaningful overall advantage or more DFE than folic acid.
At the same time, 5-MTHF presents three practical drawbacks for our intended use:
- Not knowing how many DFEs 5-MTHF truly provides
- Limited evidence about its long-term effects for supporting healthy blood flow
- A generally higher price than folic acid supplements.
That is why we selected the seemingly paradoxical option: folic acid over 5-MTHF.
If our evidence-based approach resonates with you, reach out and let us know about any vitamin or supplement marketing claim you would like us to investigate.
Sincerely,
Derek Tang, PhD, MS, BSPharm
Truth Full Health
Your Trusted Supplement Partner
Disclaimer: All blogged content is for informational purposes only and does not replace professional medical advice. Statements made about vitamins or supplements (officially called “dietary supplements”) have not been evaluated by the U.S. Food and Drug Administration (FDA). Dietary supplements are not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare provider before beginning any new supplement, diet, or lifestyle program.
[1] Title: Supplementation with Folic Acid or 5-Methyltetrahydrofolate and Prevention of Neural Tube Defects: An Evidence-Based Narrative Review. First author: MdL Samaniego-Vaesken. Journal: Nutrients. Year of publication: 2024.
[2] Title: Is there a multidisciplinary role for 5-methyltetrahydrofolate? The obstetric evidence in perspective
First author: M Rubini. Journal: European Review for Medical and Pharmacological Sciences. Year of publication: 2024
[3] Centers for Disease Control and Prevention. MTHFR gene variant and folic acid facts. Updated May 27, 2025. Accessed July 25, 2026. https://www.cdc.gov/folic-acid/data-research/mthfr/index.html
[4] Office of Dietary Supplements, National Institutes of Health. Folate: fact sheet for health professionals. Updated November 30, 2022. Accessed July 25, 2026. https://ods.od.nih.gov/factsheets/Folate-HealthProfessional/
[5] For adults aged 19 and older, the daily upper limit of folic acid intake is 1,000 mcg from supplements or fortified foods.
[6] US Food and Drug Administration. Converting units of measure for folate, niacin, and vitamins A, D, and E on the Nutrition and Supplement Facts labels: guidance for industry. Published August 2019. Accessed July 24, 2026. https://www.hhs.gov/guidance/sites/default/files/hhs-guidance-documents/FDA/Guidance-Converting-Units-of-Measure-for-Folate-Niacin-Vitamins-A-D-E-on-Nutrition-Facts-Labels.pdf
[7] Title: Effects of B Vitamins and Omega 3 Fatty Acids on Cardiovascular Diseases: A Randomised Placebo Controlled Trial. First author: P. Galan. Journal: BMJ. Year of publication: 2010.
[8] Centers for Disease Control and Prevention. Folic acid: sources and recommended intake. Updated June 2, 2026. Accessed July 25, 2026. https://www.cdc.gov/folic-acid/about/intake-and-sources.html