L-Methylfolate (5-MTHF)

aka Folate or vitamin b9.

Note

Delay taking any supplements for 30-60 minutes after consuming coffee as it contains compounds (polyphenols) that limit the absorption of many micronutrients.

Forms/Types

This is the active form of folate, which is superior to the synthetic kind (particularly for some populations).

Quality

As with all supplements - buyer beware. It's quite common for supplements to be contaminated with a variety of impurities, often in the form of heavy metals, and/or contain far more or less of the ingredients stated on the label. There's no simple rule of thumb to avoid this, such as avoiding cheap or imported products; expensive or well-known brands produced in-country may be just as bad. Ideally you should take some time to find products (if you can) that;

have been laboratory tested on behalf of the manufacturer by a reputable body or company that operates in your country or region (here's an example of a Peak Supps creatine supplement available on Amazon in the UK which has been tested by Eurofins: Creatine Monohydrate Powder 1Kg | Pure Micronised | Packaging May Vary - see pictures 3 & 4)
in the UK & EU, are manufactured in facilities that meet the minimum standards of good manufacturing practice (GMP) in their production processes (for medicines).¹² Facilities are inspected for compliance and manufacturers' product(s) must:
- be of consistent high quality
- be appropriate to their intended use
- meet the requirements of the marketing authorisation (MA) or product specification

Be wary of any manufacturers or brands making claims around these valid but irrelevant standards;

HACCP: this standard relates to food safety which indicates that the seller is claiming their supplement is a food; whilst meeting this standard is worthwhile, GMP (detailed above) would be a more appropriate standard
ISO22000: same as HACPP
ISO9001: this standard is focussed on quality control management systems in the context of managing a business or organisation, not directly on the the quality of the products that business produces (although it may have a beneficial impact)

Dosage - How Much?

1-2g.

Deficiency - Too Little

Toxicity - Too Much

Side Effects

When to Avoid Use - Interactions/Contraindications

Genetic Factors

The enzyme that converts folate into 5-MTHF is called methylenetetetrahydrofolate reductase (MTHFR). This enzyme is coded by the MTHFR gene. Two common mutations in this gene (C677T/rs1801133 and A1298C/rs1801131) can reduce this enzymes activity and slow conversion of folate. This may impair the process of methylation, which can lead to chronic inflammation, DNA damage and elevated homocysteine levels.

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Last Updated: 2026-03-05