Riboflavin (Vitamin B2)

What Riboflavin Does

Riboflavin is converted into two flavin cofactors, FMN and FAD, that run hundreds of oxidation-reduction reactions in the mitochondria. Two of them matter for methylation. MTHFR, the enzyme that makes 5-methylfolate, uses FAD. And the activation of vitamin B6 needs FMN. Subclinical riboflavin deficiency is probably common but rarely detected, because the status marker — the erythrocyte glutathione reductase activation coefficient (EGRac) — is almost never measured.

The MTHFR TT Story

The MTHFR 677TT variant produces a thermolabile enzyme that loses its FAD cofactor more easily. Supplying riboflavin should stabilise it — and in trials from one research group, it did:

• Homocysteine: 1.6 mg/day for 12 weeks lowered homocysteine by 22% in TT carriers (16.1 to 12.5 µmol/L), and by 40% in those starting with low riboflavin status. No effect in CC or CT.
• Blood pressure, cardiovascular patients: over 16 weeks in 181 patients, TT blood pressure fell from 144/87 to 131/80 mmHg; other genotypes did not respond.
• Blood pressure, treated hypertension: in 91 TT patients already on medication, systolic pressure fell a further 5.6 mmHg versus placebo; diastolic did not change significantly.
• Population data: in 6,076 Irish adults, TT combined with low riboflavin status tripled the odds of hypertension.

These are small trials (31–91 TT participants), from a single group whose members hold patents on riboflavin for hypertension, without independent replication. The dose, though, is roughly the daily requirement and carries no risk. The full context is in MTHFR Variants: What the Evidence Actually Supports.

Migraine Prevention

At 400 mg/day — 250 times the requirement — riboflavin is a migraine preventive. In a three-month randomised trial in 55 adults, 59% on riboflavin versus 15% on placebo halved their headache days. A 2022 meta-analysis of nine studies (673 participants) found fewer migraine days, shorter attacks and less pain, though with high heterogeneity. A trial in children at 200 mg/day was null. Because a single oral dose absorbs at most about 27 mg, the 400 mg is best split.

Safety

No toxicity is known and no upper limit has been set in the US or EU. Excess is excreted in urine, which turns bright yellow. Diarrhoea and increased urination were the only adverse events at 400 mg in the migraine trial.

Where It Fits

Riboflavin 1.6 mg is the genotype-specific Layer 3 of the Methylation Support Protocol, for known MTHFR 677TT carriers whose homocysteine stays raised after B12 and folate — or who also have high blood pressure.

Related Research

• MTHFR Variants: What the Evidence Actually Supports
• Homocysteine: What Your Level Means and How to Lower It
• The Methylation Support Protocol: Test, Then Target
• Methylfolate