Pyridoxine

Other name(s):

vitamin B6, pyridoxal phosphate, pyridoxamine, pyridoxol, pyridoxyl-5-phosphate

General description

Pyridoxine, also known as vitamin B6, is a water-soluble vitamin. Like the other B vitamins, pyridoxine plays an important role in energy production. B-6 was isolated in 1939. It is required for the proper functioning of more than 60 enzymes in the body, especially in the synthesis of non-essential amino acids.

Pyridoxine is essential for the synthesis of neurotransmitters such as gamma-aminobutyric acid (GABA), epinephrine, norepinephrine, dopamine, and serotonin. This vitamin is necessary in the conversion of glycogen (stored energy) to glucose (blood sugar). As a result, deficiencies can lead to sensory changes (e.g., numbness or tingling) in the extremities (peripheral neuropathy) and seizures. This vitamin is important in the formation of red blood cells, specifically the incorporation of iron into hemoglobin. Therefore, a deficiency of pyridoxine can result in anemia.

Medically valid uses

Pyridoxine is used to treat drug-induced or diet-related pyridoxine deficiency and metabolic problems such as B6-dependent convulsions, B6-responsive anemia, and some inborn errors of metabolism (genetic disorders). It is used to control nausea and vomiting in pregnant women.

Unsubstantiated claims

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Pyridoxine can be useful in decreasing PMS and preventing water retention. It acts as a diuretic, especially in PMS, and is purported to slow the aging process. It may also lower cholesterol levels, prevent atherosclerosis (hardening of the arteries), prevent the development of carpal tunnel syndrome, and prevent migraines.

Recommended intake

As indicated below, pyridoxine is measured in milligrams. It is available in tablet form, ranging in strength from 25 to 100 mg, with a 100 mg time-release tablet also available. The RDA is the Recommended Dietary Allowance.

Adults (over 18 years old)

Recommended Dietary Allowances (RDAs) of vitamin B6: Males 19–50 years, 1.3 mg; males 51 years and older, 1.7 mg; females 19–50 years, 1.3 mg; females 51 years and older, 1.5 mg. Some researchers think the RDA for women 19 to 50 years old should be increased to 1.5–1.7 mg per day; pregnant women, 1.9 mg; and lactating women, 2 mg.

Recommended maximum daily intake of vitamin Bfor adults, including pregnant and lactating women (over 18 years) is 100 mg. A doctor and pharmacist should be consulted for dosing in other conditions.

Children (under 18 years old)

Recommended Dietary Allowances (RDAs) of vitamin B6: Infants 0–6 months, 0.1 mg; infants 7–12 months, 0.3 mg; children 1–3 years, 0.5 mg; children 4–8 years, 0.6 mg; children 9–13 years, 1 mg; males 14–18 years, 1 mg per day; females 14–18 years, 1.2 mg per day.

Recommended maximum daily intake of vitamin B6: Children 1–3 years, 30 mg; children 4–8 years, 40 mg; children 9–13 years, 60 mg. Males, females (including pregnant and lactating females) 14–18 years, 80 mg.

Note: The requirement for pyridoxine increases with increased protein in the diet.

Food source

Nutrient content per 100 grams

Brewer's yeast

3.78 mg

Rice

3.59 mg

Sunflower seeds

3.59 mg

Soybeans

2.0 mg

Lentils

1.69 mg

Salmon

0.97 mg

Tuna

0.89 mg

Bran

0.85 mg

Carrots

0.65 mg

Avocado

0.6 mg

Canning vegetables may destroy over half of the pyridoxine function as a result of the heating process. Similarly, freezing vegetables may destroy up to one-third of the B6 activity.

Although pyridoxine is relatively stable in heat (and therefore does not need to be refrigerated), it is unstable in light (specifically in ultraviolet light). Therefore, it is best stored at room temperature in light-resistant containers and left unfrozen.

There is an increased need for pyridoxine if you have a high-protein diet, asthma, breast cancer, diabetes, or sickle cell anemia. Pyridoxine supplements are given to patients taking isoniazid, cycloserine, and penicillamine because these drugs interfere with the availability of the vitamin.

If you consume moderate to large amounts of alcohol, or if you are a smoker, you need additional pyridoxine.

Women who are pregnant or breastfeeding may need to take vitamin supplements, but must consult a physician before doing so.

Four common problems are associated with pyridoxine deficiency. These are seizures in infants, dermatitis, anemia (both microcytic and hypochromic), and peripheral neuropathy (nerve damage).

Pyridoxine deficiency can cause seizures in infants whose mothers took large doses of pyridoxine to control nausea and vomiting during pregnancy. The seizures may begin within a few hours to several months after birth. They are easily controlled with pyridoxine.

The anemia resulting from a pyridoxine deficiency produces smaller than normal red blood cells (microcytic) with less than normal amounts of hemoglobin (hypochromic). In this type of anemia, the serum levels of iron are typically normal or elevated, suggesting that iron is not being incorporated into hemoglobin in the absence of vitamin B6.

Side effects, toxicity, and interactions

Megadoses of pyridoxine can cause changes in sensation, such as numbness or tingling (sensory neuropathy). An abnormal gait (ataxia) may be a byproduct of peripheral neuropathy caused by excessive doses of pyridoxine.

Pyridoxine reduces the effectiveness of levodopa (a drug used to treat Parkinson's disease). Pyridoxine can increase the body's ability to metabolize (breakdown) the levodopa. This effect is not seen with patients taking a combination of levodopa and carbidopa.

Pyridoxine supplements are warranted for patients taking isoniazid, cycloserine, and penicillamine, as these drugs decrease the availability of the vitamin.

Although there are reports that high doses of pyridoxine will decrease the effectiveness of phenobarbital, primidone, and phenytoin, the proof of this interaction has not been established.

Additional information

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