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Vitamin B - 6

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Vitamin B-6 (Pyridoxine) is a component of the water-soluble vitamin B-complex vitamins. It is composed of three closely related chemical compounds: pyridoxine, pyridoxal, and pyridoxamine. These three compounds are metabolically and functionally interrelated and are readily interconverted.

Vitamin B-6 is involved in protein, fat, and carbohydrate metabolism, and is a component of the molecular configuration of many enzymes. Vitamin B-6 functions primarily in the reactions involved in the nonoxidative degradation of amino acids.

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Method of Action

Vitamin B-6 is found in cells in the active form as coenzyme pyridoxal phosphate, as well as in its amino form, pyridoxamine phosphate.

Vitamin B-6 participates in transamination. Vitamin B-6 catalyzes the reaction by acting as a carrier of the amino group. During transamination, pyridoxal phosphate accepts an amino group from an amino acid, and is subsequently converted to pyridoxamine phosphate. The amino group is then transferred to a receptor molecule (usually alpha-keto glutarate), and pyridoxal phosphate is regenerated. Transamination reactions can occur between any amino acid and a receptive alpha-keto acid.

Other metabolic processes catalyzed by vitamin B-6 are: deamination; decarboxylation, the removal of carbon dioxide from amino acids, a necessary step required for the synthesis of neurotransmitters from certain amino acids; and desulfuration, the transfer of a sulfur group from methionine to serine in order to form cysteine. All three processes utilize vitamin B-6 as a carrier compound. Vitamin B-6 is also involved in the formation of niacin from tryptophan.

Vitamin B-6 is an important enzyme in the biosynthesis of hemoglobin and in the production of gamma-aminobutyric acid (GABA) from glutamic acid.

Vitamin B-complex, vitamin B-1, vitamin B-2, vitamin C, Pantothenic acid, magnesium, potassium, linoleic acid, and sodium assist in the absorption of vitamin B-6. Absorption is decreased by tobacco, alcohol, coffee, oral contraceptive, and exposure to radiation; it is destroyed by cooking.

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Properties and Uses

Vitamin B-6 is used to treat anemic patients when the anemia is due to vitamin B-6 deficiency.

Vitamin B-6 supplements can help correct the depression, malaise, glucose intolerance and increased tryptophan excretion in some women using oral contraceptives.

Treatment with large doses of vitamin B-6 may prevent the effects of isoniazid, a chemotherapeutic agent for tuberculosis. Vitamin B-6 doses may prevent isoniazid from inhibiting the conversion of glutamic acid, the only amino acid the brain metabolizes.

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Consequences of Deficiency

Deficiency of vitamin B-6 can cause seizures by inhibiting the synthesis of gamma-aminobutyric acid (GABA). GABA is a calming chemical and seizures can result if it is present in insufficient amounts.

Vitamin B-6 deficiency has been shown to increase urinary oxalate excretion. This represents the body’s inability to convert glyoxalate to glycine, which is necessary to synthesize glycine and serine.

Deficiency in vitamin B-6 can be created by the use of oral contraceptives, with subsequent symptoms including depression and increased urinary excretion of tryptophan.

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Toxicity Levels

The toxicity of vitamin B-6 is extremely low. Sleepiness may follow an injection of large doses (100 milligrams). Extremely large (200 mg) doses may result in nerve ending damage in certain individuals.

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Recommended Dietary Allowances

RDA for adults:

2.0 mg

RDA for children:

1.2 mg

RDA for infants

0.4 mg

RDA for pregnancy:

2.5 mg

RDA for lactation:

2.5 mg

A deficiency of vitamin B-6 is unlikely in the presence of generally good diet. However women taking oral contraceptives may end up with a deficiency in spite of having at least the RDA in the daily dietary input. This is true of several other drugs also. Since pyridoxine is involved in amino acid metabolism, the need for pyridoxine varies with dietary protein intake. For adults, approximately one mg daily is minimal. The RDA standard is two milligrams per day for adults to ensure a safety margin for variances in individual need. However this safety margin is eliminated rapidly in the contest with a number of pharmaceutical drugs.

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Food Sources

• Organ Meats

• Brewer’s Yeast

• Brown Rice

• Ocean Fish

• Wheat Germ

• Walnuts

• Avocados

• Bananas

• Cabbage

• Carrots

• Corn

• Green Peas

• Pears

• Rye Bread

• Potatoes

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Summary Deficiency Symptoms


• Depression

• Anemia

• Sleepiness

• Loss of Appetite

• Nausea

• Vomiting

• Soreness of Lip and Tongue

• Dermatitis

• Conjunctivitis

• Kidney Stones


• Diabetes

• Low Serotonin Levels

PMS Symptoms Such As:
• Depression
• Puffy Fingers and Ankles
• Irritability
• Breast Discomfort
• Tiredness
• Swollen Abdomen

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