Vitamin B6 (Pyridoxine)
Vitamin B6 is a family of six related compounds; pyridoxal-5-phosphate (PLP) is the active coenzyme form. It participates in over 100 enzymatic reactions — protein metabolism, neurotransmitter synthesis (serotonin, dopamine, GABA), and haemoglobin formation. It has one of the narrowest safety margins among water-soluble vitamins.
Daily requirements
- Adults 19–50: 1.3 mg/day.
- Men 51+: 1.7 mg/day.
- Women 51+: 1.5 mg/day.
- Pregnancy: 1.9 mg/day.
- Lactation: 2.0 mg/day.
- Tolerable Upper Intake Level: 100 mg/day — above this, risk of sensory neuropathy rises with duration.
Toxicity — the sensory neuropathy risk
Chronic supplementation at 100–200 mg/day or more for months to years can cause a dose-dependent sensory neuropathy — tingling, numbness, and impaired proprioception in hands and feet. Reports exist even below the UL. If you take a B-complex, check the B6 dose — many products contain 25–100 mg per pill, and stacking with a multivitamin can easily exceed safe chronic intake. Symptoms are usually reversible if caught early.
Clinical uses with evidence
- Morning sickness (nausea of pregnancy) — B6 10–25 mg every 6–8 hours is a first-line, safe intervention (ACOG guideline). Often combined with doxylamine (Diclegis / Diclectin).
- PMS symptoms — B6 up to 80 mg/day showed modest benefit in a Cochrane meta-analysis. Doses above 100 mg increase neuropathy risk with limited additional benefit.
- Hyperemesis gravidarum — adjunctive to standard antiemetic therapy.
- Carpal tunnel syndrome — traditional use lacks good randomised evidence.
Deficiency
Rare in isolation; more often part of general B-complex deficiency in alcoholism, malabsorption, or extended isoniazid therapy for tuberculosis (which depletes B6). Symptoms: microcytic anaemia, dermatitis, glossitis, depression, confusion, and seizures in severe cases. Isoniazid patients are routinely co-prescribed pyridoxine 25–50 mg/day.
Food sources
- Chickpeas (1 cup cooked): 1.1 mg
- Beef liver (3 oz): 0.9 mg
- Yellowfin tuna (3 oz): 0.9 mg
- Salmon (3 oz): 0.6 mg
- Chicken breast (3 oz): 0.5 mg
- Potato (1 medium baked): 0.4 mg
- Banana (1 medium): 0.4 mg
- Fortified breakfast cereal: 0.5–2 mg