Vitamin B6

Figure 1. The chemical structure of pyridoxal 5'-phosphate, the active form of Vitamin B6.

Vitamin B6 or Pyridoxine is a micronutrient and one of eight essential B vitamins. Vitamin B6 refers to a group of six chemically similar compounds, i.e., "vitamers", which can be converted in the human body to the active form, pyridoxal 5'-phosphate (PLP), which serves as a coenzyme in more than 140 enzyme reactions related to amino acid, glucose, and lipid metabolism. PLP also helps enzymes to maintain normal levels of homocysteine and to support immune function and brain health.

Vitamin B6 is synthesised in plants to protect against ultraviolet B radiation and to participate in the synthesise of chlorophyll. Animals, including humans, cannot synthesise Vitamin B6, hence can only obtain it from their diet. Vitamin B6 is a water soluble vitamin and any excesses in the body is passed out through the urine.

Food Sources

Vitamin B6 is found in a variety of animal and plant foods. Examples include:

• Beef liver
• Tuna
• Salmon
• Fortified cereals
• Chickpeas
• Poultry
• Dark leafy greens
• Bananas, papayas, oranges, and cantaloupe

Taken as a Dietary Supplement

As a dietary supplement, Vitamin B6 is used to treat Vitamin B6 deficiency. While rare, Vitamin B6 deficiency can occur when other B vitamins in the body are low, particularly Vitamin B12 and Folic Acid. Certain diseases and conditions may also inhibit the absorption of Vitamin B6, including kidney disease; autoimmune intestinal disorders like celiac disease, ulcerative colitis, and Crohn’s disease; and autoimmune inflammatory disorders such as rheumatoid arthritis. Severe or prolonged Vitamin B6 deficiency may exhibit the following symptoms:

• Microcytic anaemia
• Skin conditions
• Depression
• Confusion
• Lowered immunity

Vitamin B6 is also promoted as a supplement for helping to lower the risk of cardiovascular diseases, improve cognitive function, lower the risk of cancer, and reduce the symptoms of morning sickness.

The Recommended Dietary Allowance for men ages 14-50 years is 1.3mg daily; 51+ years, 1.7mg daily. For women ages 14-18 years, it is 1.2mg daily; 19-50 years, 1.3mg daily; and 51+ years, 1.5mg daily. For pregnancy and lactation, the amount increases to 1.9mg and 2.0 mg daily, respectively. The Tolerable Upper Intake Level for adults 19+ years is 100mg daily, with slightly lesser amounts in children and teenagers.

Vitamin B6 toxicity can occur from long-term very high dose supplementation of greater than 1000 mg daily. Symptoms of toxicity include neuropathy in feet and hands, ataxia, and nausea.

Background

Vitamin B6 (Pyridoxine) is listed in the World Health Organization's List of Essential Medicines.