Vitamin B6 - pyridoxine

Vitamin B6 exists as pyridoxine, pyridoxal and pyridoxamine. The metabolically active coenzyme forms are pyridoxal phosphate (PLP) and pyridoxamine phosphate (PMP).

These coenzymes are involved in more than 100 enzyme reactions. Both PLP and PMP are involved in amino acid metabolism, and PLP is also involved in the metabolism of carbohydrates, and lipids.

Vitamin B6 plays a role in cognitive development through the biosynthesis of neurotransmitters and in maintaining normal levels of homocysteine, an amino acid in the blood.

Vitamin B6 is involved in gluconeogenesis (formation of glucose from protein) and glycogenolysis (break down of glycogen), immune function and hemoglobin formation.

Sources

Vitamin B6 is widely distributed in foods. The richest sources are fish, beef liver and other organ meats, potatoes and other starchy vegetables, and fruit (other than citrus).

In the United States, adults obtain most of their dietary vitamin B6 from fortified cereals, beef, poultry, starchy vegetables, and some non-citrus fruits. Here is a list of foods having the highest content of vitamin B6.

Daily intake

The recommended daily intake is as follows:

Males 14-50 years: 1.3 milligrams

Males 51 years and older: 1.7 milligrams

Females 9-13 years: 1.0 milligram

Females 14-50: 1.2 milligrams

Females 51 years and older: 1.5 milligrams

Pregnant females of any age: 1.9 milligrams

Lactating females of any age: 2.0 milligrams

The Tolerable Upper Intake Level (UL) is 100 milligrams for adults.

Deficiency

Isolated vitamin B6 deficiency is uncommon.

Inadequate vitamin B6 status is usually associated with deficiency of vitamin B12 and folic acid.

Vitamin B6 deficiency is associated with anemia, dermatitis with cheilosis (scaling on the lips and cracks at the corners of the mouth) and glossitis (swollen tongue), depression and confusion, and weakened immune function.

Individuals with borderline vitamin B6 concentrations or mild deficiency might have no deficiency signs or symptoms for months or even years.

In infants, vitamin B6 deficiency causes irritability, abnormally acute hearing, and convulsive seizures

Excess

Vitamin B6 is usually safe up to 50 mg per day in adults.

However, vitamin B6 can cause neurological disorders, such as loss of sensation in legs and imbalance, when taken in high doses (200 mg or more per day) over a long period of time.

Vitamin B6 toxicity can damage sensory nerves, leading to numbness in the hands and feet as well as difficulty in walking.

Symptoms of a pyridoxine overdose may include poor coordination, staggering, numbness, decreased sensation to touch, temperature, and vibration, and tiredness for up to six months

References: 1 , 2 , 3 , 4