Vitamin B2 (Riboflavin)
Riboflavin is the precursor to FAD and FMN, redox cofactors central to mitochondrial energy production. Deficiency alone is rare in high-income countries but common as part of general B-complex insufficiency in alcoholism and severe undernutrition. Riboflavin has one well-established therapeutic use — migraine prevention.
Daily requirements
- Adult men: 1.3 mg/day.
- Adult women: 1.1 mg/day.
- Pregnancy: 1.4 mg/day.
- Lactation: 1.6 mg/day.
- No Tolerable Upper Intake Level — excess is renally excreted (as riboflavin's bright yellow pigment).
Migraine prevention
Riboflavin 400 mg/day has Level B evidence from the American Academy of Neurology for migraine prophylaxis. The seminal 1998 Schoenen trial showed a 50% reduction in migraine frequency in about half of participants after 3 months. Response is slow (allow 2–3 months). It's cheap, safe, and worth trying before or alongside prescription preventives like topiramate or CGRP antagonists.
Ariboflavinosis (deficiency)
Cheilosis (cracks at corners of the mouth), angular stomatitis, glossitis, seborrhoeic dermatitis, corneal vascularisation, and normocytic-normochromic anaemia. Usually responds within days to riboflavin 5–10 mg/day. Common in alcoholism, anorexia, and breast-fed infants of B2-deficient mothers.
MTHFR polymorphism
Riboflavin is a cofactor for methylenetetrahydrofolate reductase (MTHFR). People homozygous for the C677T polymorphism (~10% of Europeans) have reduced enzyme activity that is partly restored by higher riboflavin intake. Small trials show riboflavin lowers blood pressure specifically in this genotype — an interesting example of nutrigenomics with clinical relevance.
The fluorescent yellow urine
Riboflavin itself is a bright yellow-green fluorescent pigment. Any dose above a few mg (which includes almost every multivitamin and B-complex) produces neon-yellow urine within hours — harmless, and actually confirms your supplement is absorbing.
Food sources
- Beef liver (3 oz): 2.9 mg — the champion source
- Fortified breakfast cereal: 0.6–2 mg
- Yoghurt, plain (1 cup): 0.5 mg
- Milk (1 cup): 0.4 mg
- Egg (1 large): 0.2 mg
- Almonds (1 oz): 0.3 mg
- Beef (3 oz): 0.4 mg
- Mushrooms, portabella (½ cup): 0.3 mg
- Spinach (½ cup cooked): 0.2 mg