MTHFR is a real gene in the folate pathway, but it often gets treated like it explains everything. This episode keeps the scale right. You’ll learn what the enzyme does, why homocysteine became a popular lab marker, and how to separate association evidence from intervention evidence so you don’t get misled by a number moving without outcomes changing. You’ll also get a simple decision model you can use without spiraling.

You’ll learn:

• What MTHFR actually does inside folate metabolism

• Why folate was historically studied in medicine

• How homocysteine became a biomarker

• Why association studies and randomized trials tell different stories

• What DNA methylation actually means

• Why this is a pathway discussion, not a personality explanation

This episode separates evidence types carefully and keeps claims proportional to data.

Timestamps

0:00 Primary intro

1:05 Why MTHFR gets inflated in conversation

2:00 Folate history and why it mattered in medicine

3:00 One carbon metabolism explained clearly

4:15 What MTHFR enzyme actually does

5:20 B12 as cofactor and why this is a pathway, not a solo gene

6:10 Homocysteine as a biomarker and what association means

7:20 Randomized trials lowering homocysteine and outcome nuance

8:40 DNA methylation defined properly

9:50 What MTHFR does not control

10:40 Mendelian randomization and causality

11:30 Micro protocol and bridge to Part 2

Key Terms

Folate: A B vitamin required for DNA synthesis and red blood cell formation. Named from the Latin “folium,” meaning leaf.

One carbon metabolism: A network of reactions that transfer single carbon units for DNA synthesis and methylation reactions.

MTHFR: Methylenetetrahydrofolate reductase, an enzyme that converts one form of folate into another needed for homocysteine recycling.

Enzyme: A protein that speeds up a chemical reaction.

Homocysteine: An intermediate amino acid in methionine metabolism that can accumulate if recycling is impaired.

Methionine: An essential amino acid involved in protein synthesis and methyl group donation.

Vitamin B12: A vitamin that acts as a cofactor for methionine synthase in homocysteine conversion.

Cofactor: A helper molecule required for an enzyme to function.

Biomarker: A measurable biological indicator, often assessed through blood testing.

Association: When two variables move together statistically; does not prove cause.

Randomized controlled trial: A study design that assigns participants by chance to test cause and effect.

DNA methylation: The addition of methyl groups to DNA that can influence gene expression levels.

Gene expression: The process by which a gene is used to produce a protein.

Mendelian randomization: A genetics based method using variants as natural experiments to estimate causality.

Keywords

MTHFR, folate cycle, homocysteine, methylation, one carbon metabolism, B12, C677T, gene expression, cardiovascular risk, Mendelian randomization

References

NIH Office of Dietary Supplements. Folate Fact Sheet for Health Professionals.

NIH Office of Dietary Supplements. Vitamin B12 Fact Sheet for Health Professionals.

HOPE 2 Investigators. NEJM. 2006.

NORVIT Trial Investigators. NEJM. 2006.

Clarke R et al. Homocysteine and vascular disease. JAMA. 2002.

Recent Mendelian randomization analyses on homocysteine and cardiovascular outcomes, 2018–2023.