MTHFR Gene Mutation: How Your Genetics Affect Folate, Homocysteine, and Brain Health

What Is the MTHFR Gene?

MTHFR (methylenetetrahydrofolate reductase) is an enzyme that plays a critical role in the methylation cycle — one of the most important biochemical processes in the body. Methylation affects DNA repair, neurotransmitter synthesis, detoxification, and gene expression.

The two most clinically significant MTHFR variants are:

• C677T — reduces enzyme activity by 40% (heterozygous) or 70% (homozygous)

• A1298C — reduces enzyme activity by 20–40%

Approximately 40–60% of people carry at least one copy of a MTHFR variant. About 10–15% are homozygous for C677T (the most impactful variant).

What Does MTHFR Affect?

Homocysteine

The most well-studied consequence of MTHFR variants is elevated homocysteine. When the methylation cycle is impaired, homocysteine accumulates in the blood.

Elevated homocysteine (> 10 μmol/L) is independently associated with:

• Cardiovascular disease — damages arterial endothelium

• Stroke — 2x increased risk at levels > 15 μmol/L

• Cognitive decline and dementia — strong association with Alzheimer's disease

• Depression and anxiety — homocysteine interferes with neurotransmitter synthesis

Folate Metabolism

MTHFR converts dietary folate (and folic acid from supplements) into 5-MTHF (5-methyltetrahydrofolate) — the active form the body can use. People with MTHFR variants cannot efficiently make this conversion.

This means standard folic acid supplements are largely ineffective for MTHFR carriers. They need the pre-converted form: methylfolate (5-MTHF).

How to Manage MTHFR

Test First

If you have a genetics report (23andMe, AncestryDNA, or a clinical genetics test), Body150 can extract your MTHFR status and adjust your reference ranges accordingly.

Key tests to order:

• Homocysteine — the functional marker; target < 8 μmol/L

• Serum folate — may be falsely normal even with MTHFR

• Active B12 (holotranscobalamin) — methylation requires B12 as a cofactor

Supplement Protocol for MTHFR Carriers

Important: Start low and increase slowly. Some people with MTHFR variants experience "overmethylation" symptoms (anxiety, irritability, insomnia) when starting methylfolate. If this happens, reduce the dose.

Lifestyle Factors

• Reduce alcohol — alcohol depletes folate and B12

• Avoid unmetabolized folic acid — check all supplements and fortified foods for synthetic folic acid

• Eat folate-rich foods — leafy greens, legumes, liver

• Manage stress — cortisol depletes methylation cofactors

Body150 automatically adjusts your homocysteine reference range and supplement recommendations based on your MTHFR status detected in uploaded genetics reports.