Vitamin B6 (Pyridoxine)

What Is Vitamin B6 (Pyridoxine)?

Vitamin B6 is a water-soluble vitamin that occurs in three main natural forms: pyridoxine (most common in plant foods), pyridoxal, and pyridoxamine (predominant in animal foods). All three are converted in the body to pyridoxal 5'-phosphate (PLP), the metabolically active coenzyme that participates in more than 100 enzymatic reactions, primarily in amino acid metabolism.

The RDA for adults aged 19-50 is 1.3 mg/day for both sexes. Adults over 50 require 1.7 mg/day (men) and 1.5 mg/day (women). The UL is 100 mg/day from all sources.

Key Functions

• Amino acid metabolism: PLP is a cofactor for transamination, deamination, and decarboxylation reactions, including the synthesis of nonessential amino acids.
• Neurotransmitter synthesis: Required for the production of serotonin, dopamine, norepinephrine, GABA, and histamine.
• Hemoglobin synthesis: PLP is needed for the synthesis of heme, the oxygen-carrying component of hemoglobin.
• Homocysteine metabolism: Along with folate and B12, B6 converts homocysteine to cysteine, reducing cardiovascular risk associated with elevated homocysteine.
• Glycogen breakdown: PLP activates glycogen phosphorylase, releasing glucose from glycogen stores.

Deficiency and Food Sources

Deficiency causes microcytic anemia, peripheral neuropathy, dermatitis, glossitis, and confusion. At very high supplemental doses (above 200 mg/day chronically), sensory neuropathy can develop even though B6 is water-soluble.

Top food sources include chickpeas, beef liver, tuna, salmon, chicken breast, potatoes, and bananas. Pyridoxine in plant foods is partially bound to glycosides and is less bioavailable than forms in animal products.