Vitamin B6 (Pyridoxal 5'-Phosphate / PLP)

Direct Answer

Vitamin B6 is a water-soluble pyridine vitamin acting via its active coenzyme Pyridoxal 5'-Phosphate (PLP) in over 140 amino acid decarboxylation, transamination, and neurotransmitter synthesis reactions. Adult RDA is 1.3–1.7 mg, with a Tolerable Upper Limit of 100 mg/day.

Source: NIH ODS / EFSA · Last reviewed Aug 28, 2026

Specs

Nutrient Type	Water-Soluble Pyridine Vitamin
Adult RDA / RDI	1.3 mg / day (Adults 19–50) / 1.7 mg (Men 51+) / 1.5 mg (Women 51+)
Tolerable Upper Limit (UL)	100 mg / day (US FDA/NIH) / 12 mg / day (EFSA, revised down from 25mg in 2023) (Avoid sensory peripheral neuropathy)
Chemical Forms	Pyridoxal 5'-Phosphate (PLP, active coenzyme), Pyridoxine HCl, Pyridoxamine
Primary Biological Function	Transamination / deamination of amino acids, Serotonin / Dopamine / GABA synthesis from amino acids, Glycogen phosphorylase cofactor, Heme synthesis
Deficiency Condition	Microcytic sideroblastic anemia, Seborrheic dermatitis, Cheilosis, Peripheral neuropathy, Convulsions
Top Whole Food Sources	Chickpeas, Wild Salmon, Yellowfin Tuna, Beef Liver, Chicken Breast, Russet Potatoes, Bananas
Neurotoxicity Threshold	Chronic megadosing of Pyridoxine HCl (>200–500mg/day) causes reversible sensory neuropathy due to competitive inhibition of tissue PLP

Neurotransmitter Decarboxylation Hub

PLP is the mandatory rate-limiting coenzyme for L-DOPA decarboxylase (producing dopamine), glutamate decarboxylase (producing GABA), and 5-HTP decarboxylase (producing serotonin).