Vitamin B6 - what is it?
Vitamin B6, New RDA* 1.4 mg
Vitamin B6 is a water-soluble vitamin. This means you need it in your diet every day because it can't be stored in the body.
Pyridoxamine and Pyridoxal are found in animal products, and Pyridoxine in animals and plants.
*Sourced from EFSA WEBSITE
Vitamin B6 - what does it do?
Involved in the use of protein, and helps to form haemoglobin in blood (the substance which carries oxygen around our bodies).
The cofactor forms of pyridoxine are pyridoxal-5’-phosphate and pyridoxamine-5’-phosphate. Pyridoxal phosphate is involved as a cofactor particularly in the metabolic transformation of amino acids, including decarboxylation, transamination and racemisation. Vitamin B6 is a cofactor in the conversion of tryptophan to 5-hydroxytryptamine and of methionine to cysteine. Pyridoxine can modify the action of steroid hormones in vivo by interacting with steroidreceptor complexes.
Pyridoxine is essential for the manufacture of prostaglandins and for the formation of red blood cells. Pyridoxine is involved in cellular replication and antibody production. An adequate supply of pyridoxine is necessary for the function of the nervous system. The vitamin is involved in the biosynthesis of several neurotransmitters, including serotonin, gamma amino-butyric acid (GABA), dopamine and noradrenaline and so has a role in the regulation of mental processes and mood.
It is also involved in sodium-potassium balance, histamine metabolism, the conversion of tryptophan to niacin, absorption of vitamin B12 and the production of hydrochloric acid in the gastrointestinal tract.
Deficiency
Pyridoxine deficiency is unusual in humans. Children who had been given milk in which the pyridoxine had been destroyed by overheating, displayed various symptoms, including weakness, irritability, nervousness, susceptibility to noise, weight loss and insomnia. Adult volunteers on a pyridoxine deficient diet became depressed and irritable, with ‘a loss of sense of responsibility’. They also experienced a greasy rash on the forehead and around the nose and cracking of the lips and tongue.
Pyridoxine dependency is a rare autosomal recessive disorder in which the enzyme glutamate decarboxylase, which is involved in the synthesis of GABA, has a defective binding site for pyridoxal phosphate. Much higher tissue levels of Pyridoxal phosphate are necessary for the enzyme to have any significant activity. The condition results in seizures of prenatal or neonatal onset and treatment with large doses of pyridoxine is necessary to prevent severe mental retardation or death.
It has also been suggested that Pyridoxine deficiency may be a factor in hyperhomocysteinaemia, which is associated with an increased risk of cardiovascular disease. Pyridoxine deficiency has also been reported to be associated with immune dysfunction, kidney stones, cancer and carpal tunnel syndrome, although the evidence for these links is variable.
Vitamin B6 - Sources
Poultry, white fish, milk, eggs, whole grains, soya beans, peanuts and some vegetables.
