Vitamin B6 - Benefits, Deficiency Symptoms And Food Sources

Alternative name :: Pyridoxine

Vitamin B6 is a water-soluble B-complex vitamin that was first isolated in the 1930s. In 1934, Gyorgy reported that vitamin B2 consists of two factors - riboflavin and vitamin B6 that prevented skin lesions in rats. Vitamin B6 was isolated in 1938 by several laboratories and its chemical structure was identified soon after.

There are six forms of vitamin B6 -pyridoxine, pyridoxal, pyridoxamine and their phosphate derivatives, pyridoxine phosphate, pyridoxal phosphate and pyridoxamine phosphate. In the body, all the three forms are equally active as precursors of the coenzyme form of the vitamin.

Since vitamin B6 is water-soluble, it is easily absorbed from the small ,intestine. The body stores of this vitamin are small, although small amounts are found throughout the body tissues. The greatest levels are found in liver, brain, kidney, spleen and muscle. Muscle serves as the largest depot of the body stores of vitamin B6.

Vitamin B6 is water-soluble, heat-stable and, acid-stable. However, it is sensitive to light and alkalis. Of the various forms, pyridoxine is more resistant to food processing and storage conditions, and probably represents the principle form in food products.

Functions of vitamin B6

The coenzyme form of vitamin B6 is Pyridoxal. Phosphate (PLP). PLP plays a vital role in the functioning of approximately 100 enzymes, most of which are involved in amino acid metabolism. Amino acids are building blocks of proteins, hence vitamin B6 plays a vital role in protein, metabolism, unlike the previous three water-soluble vitamins which are required for metabolism of all three energy yielding nutrients - carbohydrates, fats and proteins. Here are few examples of enzyme systems which depend on vitamin B6.

Decarboxylation :- It involves removal of carboxyl group (COOH). This reaction converts glutamic acid (an amino acid) to GABA (Gamma Amino Butyric Acid, a substance found in the gray matter of the brain. Decarboxylation also converts tryptophan (an amino acid) to serotonin, a neurotransmitter.

Transamination :- This reaction involves transfer of amino group (-NH2) from one compound to another forming amino acids. Transamination reactions enable us to synthesize several amino acids within our body even if we do not get them from our diet in sufficient amounts.

Transulphuration :- This involves the removal and transfer of sulphur groups from one amino acid to another.

Tryptophan conversion to niacin :- In the previous chapter, it was mentioned that niacin can be synthesized from tryptophan in our body. This conversion is a multi step process, one of which is catalysed by vitamin B2 Thus, adequate vitamin B2 in the diet reduces the requirement for dietary niacin.

Haemoglobin synthesis :- PLP functions as a coenzyme in the synthesis of haeme, a component of haemoglobin. Haemoglobin is found in the red blood cells and its deficiency leads to anemia.

Nucleic acid synthesis :- PLP acts as a coenzyme for a key enzyme involved in the synthesis of nucleic acids (DNA and RNA).

Pyridoxal phosphate is also required for deamination reactions, for the breakdown of glycogen to glucose, for formation of antibodies, and probably for the synthesis of unsaturated fatty acids in the body.

Vitamin B6 supplements are also used in pharmacologic doses for the treatment of certain; conditions such as premenstrual syndrome, depression, and nausea and vomiting during pregnancy.

Benefits of vitamin B6

Vitamin B6 is beneficial if you suffer from water retention , and is necessary for the production of hydrochloric acid and the absorption of fats and protein. Vitamin B6 also aids in maintaining sodium and potassium balance, and promotes red blood cell formation. Vitamin B6 regulates the balance between sodium and potassium in the body, which is vitally important for normal body functions. It is also required for absorption of vitamin B12 and for the production of hydrochloric acid and magnesium. It is helpful in the treatment of allergies, arthritis, and asthma.

Daily allowances of vitamin B6

The minimum Recommended Dosage Allowance of Vitamin B 6 are :-

• Men - 2 mg.
• Women - 1.6 mg.
• Pregnant women - 2.2 mg.

Rich sources of vitamin B6

Good dietary sources of vitamin B6 include chicken, turkey, tuna, salmon, shrimp, beef liver, lentils, soybeans, nuts, avocados, bananas, carrots, brown rice, bran, sunflower seeds, wheat germ, and whole-grain flour.

Deficiency of vitamin B6

Irritability, nervousness and insomnia as well as general weakness, skin changes such as dermatitis and acne as well asthma and allergies might develop when pyridoxine is in short supply. Symptoms may include nails that are ridged, an inflamed tongue as well as changes to your bones - which can include osteoporosis and arthritis. Kidney stones may also appear. Inadequate intake of the vitamin may also lead to loss of muscular control, migraine headaches, diseases of old age, and premature senility. Carpal tunnel syndrome has been linked to a deficiency of vitamin B6 as well.

Pregnant women and women using oral contraceptive pills also have increased requirements of this vitamin, and they are at higher risk of deficiency.

Vitamin B6 deficiency has also been observed in infants who have been fed synthetic milk or food lacking in vitamin B6. The infants showed nervous irritability and convulsive seizures. The convulsions respond dramatically to supplements of vitamin B6.

Vitamin B6 toxicity

Acute toxicity of vitamin B6 is rare. However, when it is taken in pharmacologic doses, as in therapy for premenstrual syndrome, toxic effects can be produced. Toxicity symptoms include depression, fatigue, irritability, headaches and lack of muscle coordination, nerve damage causing numbness and muscle weakness leading to inability to walk. Mega doses of vitamins should be used with caution. Because of interrelationships in metabolism of various nutrients, mega dose of a vitamin can induce deficiency of other vitamins.