VITAMIN B6

Vitamin B6, a part of the vitamin B complex group, is a water-soluble vitamin metabolized in the liver. Although there are several recognized forms, PLP (pyridoxal phosphate) is the active form and cofactor in many aspects of amino acid metabolism, and is necessary for the enzymatic reaction that governs the release of glucose and glycogen.


The seven forms of vitamin B6 are as follows:

1. Pyridoxine (PN): most commonly given as vitamin B6 supplement
2. Pyridoxine 5'-phosphate (PNP)
3. Pyridoxal (PL)
4. Pyridoxal 5'-phosphate (PLP): the metabolically active form (sold as 'P-5-P' vitamin supplement)
5. Pyridoxamine (PM)
6. Pyridoxamine 5'-phosphate (PMP)
7. 4-Pyridoxic acid (PA): the catabolite which is excreted in the urine

All forms of vitamin B except PA can be inter-converted.

Vitamin B6: Functions in the Human Body

Pyridoxal phosphate, the metabolically active form of vitamin B6 is involved in macronutrient metabolism, histamine synthesis, neurotransmitter synthesis, hemoglobin synthesis, and gene expression. Pyridoxal phosphate serves as a coenzyme and facilitates decarboxylation, transamination, racemization, elimination, replacement and beta-group inter-conversion reactions. Vitamin B6 is involved in over 100 chemical processes in the body per minute. These processes include the production of amino acids, creating neurotransmitters such as serotonin, metabolizing energy, and balancing a range of hormones. Like other B-vitamins, B6 also strengthens the immune system.

Vitamin B6: Recommended Daily Intake

The recommended RDI for vitamin B6 is displayed below.

• Infants up to 6 months old: 100mcg
• 6 - 12 months old: 300mcg
• 1 - 3 years old: 500mcg
• 4 - 8 years old: 600mcg
• Males 9 - 13 years old: 1mg
• Males 14+: 1.3mg
• Females 9 - 13 years old: 1mg
• Females 14 - 50 years old: 1.2mg
• Females 50+: 1.5mg
• Pregnant females all ages: 1.9mg
• Lactating females all ages: 2mg

Deficiency of B6 alone is rare and usually associated with a deficiency in other B-vitamins. Alcoholics and the elderly are most at risk, and availability to the body may be impaired by certain drugs such as anticonvulsants and corticosteroids. Clinical B6 deficiency syndrome is a seborrhoeic dermatitis outbreak and neurological symptoms of somnolence, confusion, and neuropathy will also occur. Less severe cases of deficiency will experience metabolic lesions and impaired glucose intolerance.

Vitamin B6: Risk of Overdose


Adverse effects of vitamin B consumption have only ever been observed in supplements and not food intake, yet although Vitamin B6 is a water soluble vitamin, excess RDI over a sustained period will result in neurological problems. Pain and numbness, and in some cases problems walking are typical symptoms of excessive consumption of pyridoxine at a level of 1,000mg per day. The Tolerable Upper Limit (TL) has been set at 100mg/pd by the US FDA (2000).

Source: Wl