Vitamin B6: benefits, dosage, contraindications
Other name(s)
Pyridoxine, pyridoxamine, pyridoxal
Scientific name(s)
Pyridoxal-5'-Phosphate, Pyridoxine
Family or group:
Vitamins
Indications
Rating methodology
EFSA approval.
Vitamin B6 Deficiency ✪✪✪✪✪
Vitamin B6 deficiency is rare, leading to seborrhea (excessive sebum secretion by sebaceous glands), glossitis, pellagroid erythema, polyneuritis, or even depression with manic episodes. Possible causes include iatrogenic factors (treatment with isoniazid or D-penicillamine) or pregnancy. In adults with vitamin B6 deficiency, the dose used is 2.5 to 25 mg per day for three weeks, followed by a maintenance dose of 1.5 to 2.5 mg per day.
Posologie
Oral route
2.5 - 25 mg
Adults
Anemia ✪✪✪✪✪
Sideroblastic anemias are anemias related to iron utilization, characterized by inadequate use of iron by the marrow for heme synthesis, despite the presence of iron in adequate or excessive amounts. Sideroblastic anemias may be acquired or congenital. Acquired sideroblastic anemias can be due, among other things, to a deficiency in vitamin B6. The most common congenital sideroblastic anemia is an X-linked form caused by heterozygous germline mutations of the ALAS2 gene (a gene involved in heme biosynthesis). As vitamin B6 (pyridoxine) is an essential cofactor of the enzyme produced by ALAS2, patients may respond to pyridoxine supplementation. Initially, vitamin B6 (pyridoxine) is used at a dose of 200-600 mg per day, then the dose is reduced to 30 to 50 mg per day if the response is adequate.
Posologie
Oral route
200 - 600 mg
Adults
Fatigue ✪✪✪✪✪
The European health authorities (EFSA, European Food Safety Authority and the European Commission) consider that products containing vitamin B6 may claim to contribute to normal energy metabolism and the reduction of fatigue.
Posologie
Oral route
1.6 - 25 mg
Adults
Emotional Balance ✪✪✪✪✪
Pyridoxine is necessary for the synthesis of many neurotransmitters, including serotonin, adrenaline, and noradrenaline. It is a cofactor of 5-hydroxytryptophan decarboxylase, which is an enzyme involved in one of the conversion steps from tryptophan to serotonin. Pyridoxine is also essential for tyrosine carboxylase, which converts tyrosine into dopamine, adrenaline, and noradrenaline. Pyridoxine deficiency is significantly associated with increased depression, fatigue, mood disturbance, and other psychological disorders.
Posologie
Oral route
1.6 - 25 mg
Adults
Hyperhomocysteinemia ✪✪✪✪✪
The oral intake of vitamin B6 (pyridoxine), alone or in combination with folic acid, is effective for treating postprandial hyperhomocysteinemia. Daily intake of 50 to 200 mg of pyridoxine reduces postprandial homocysteine levels by 32% to 35%. However, vitamin B6 seems to reduce homocysteine concentrations in patients with folic acid and vitamin B12 deficiencies, especially when combined with folic acid and vitamin B12 supplements. Pyridoxine has no effect on fasting homocysteine levels.
Posologie
Orally
16 mg
Adults
Synergies
Lowering blood homocysteine with folic acid based supplements: meta-analysis of randomized trials.
The effect of different treatment regimens in reducing fasting and postmethionine-load homocysteine concentrations.
Effects of folic acid and combinations of folic acid and vitamin B12 on plasma homocysteine concentrations in healthy young women.
Diagnosis and treatment of hyperhomocysteinemia.
Folic acid--an innocuous means to reduce plasma homocysteine.
Relationship between plasma homocysteine and vitamin status in the Framingham study population. Impact of folic acid fortification.
Combination of low-dose folic acid and pyridoxine for treatment of hyperhomocysteinaemia in patients with premature arterial disease and their relatives.
Homocysteine and coronary atherosclerosis.
AMD ✪✪✪✪✪
A large-scale clinical study conducted on women over 40 years old with a history of cardiovascular disease or presenting risk factors for cardiovascular disease showed that the daily intake of 50 mg of vitamin B6 (pyridoxine), along with 1000 mcg of vitamin B12 (cyanocobalamin) and 2500 mcg of folic acid, over an average of 7.3 years significantly reduces the risk of developing AMD compared to placebo,
Posologie
Orally
50 mg
Women
Synergies
Kidney Stones ✪✪✪✪✪
Most kidney stones are composed of calcium oxalate, and high urinary oxalate levels are associated with an increased risk of developing kidney stones. Vitamin B6 seems to reduce urinary oxalate excretion in some patients. Indeed, in patients with primary hyperoxaluria type I, vitamin B6 (pyridoxine) appears to reduce stone formation by shifting the degradation of the oxalic acid precursor, glyoxylic acid, towards glycine. In patients with primary hyperoxaluria type I, vitamin B6 (pyridoxine) has been used at a dose of 25 to 500 mg per day.
Posologie
Orally
25 - 500 mg
Adults
Kidney stones. Medical management and newer options for stone 'removal'.
Response to a physiologic dose of pyridoxine in type I primary hyperoxaluria.
Control of hyperoxaluria with large doses of pyridoxine in patients with kidney stones.
Primary hyperoxaluria: effect of treatment with vitamin B6 and shock waves.
The evaluation of some biochemical parameters in pyridoxine-treated calcium oxalate renal stone formers.
Mild metabolic hyperoxaluria and its response to pyridoxine.
Nausea and Vomiting ✪✪✪✪✪
Oral intake of vitamin B6, usually at a dose of 25 mg every 8 hours for 3-4 days, reduces nausea and vomiting during pregnancy. The American College of Obstetrics and Gynecology considers pyridoxine a first-line treatment for pregnancy-induced nausea and vomiting. However, it is unclear if pyridoxine is the most effective for managing pregnancy-induced nausea and vomiting. Some research suggests that pyridoxine improves severe nausea more than mild to moderate nausea. A lower dose of pyridoxine, at 10 mg every eight hours, improves nausea, but does not seem to significantly improve vomiting during pregnancy.
Posologie
Orally
10 - 25 mg
4 - days
Women
Vitamin B6 is effective therapy for nausea and vomiting of pregnancy: a randomized, double-blind placebo-controlled study.
ACOG (American College of Obstetrics and Gynecology) Practice Bulletin: nausea and vomiting of pregnancy.
Pyridoxine for nausea and vomiting of pregnancy: a randomized, double-blind, placebo-controlled trial.
Comparison of the effectiveness of ginger and vitamin B6 for treatment of nausea and vomiting in early pregnancy: a randomized double-blind controlled trial.
Premenstrual Syndrome ✪✪✪✪✪
Clinical evidence has shown that oral intake of vitamin B6 (pyridoxine) can improve premenstrual syndrome (PMS) symptoms such as pain, breast tenderness, and depression in some patients. The combination of 50 mg of pyridoxine and 200 mg of magnesium oxide per day appears to relieve anxiety and other PMS-related symptoms.
Posologie
Orally
50 - 100 mg
Women
Efficacy of vitamin B-6 in the treatment of premenstrual syndrome: systematic review.
A synergistic effect of a daily supplement for 1 month of 200 mg magnesium plus 50 mg vitamin B6 for the relief of anxiety-related premenstrual symptoms: a randomized, double-blind, crossover study.
Stroke ✪✪✪✪✪
A meta-analysis of 10 clinical trials including over 44,000 patients shows that B vitamin supplementation slightly reduces the relative risk of stroke by 10% compared to placebo in patients at risk or with a history of cardiovascular disease. However, it is still unknown which specific combination of B vitamins is optimal for stroke risk reduction in patients with cardiovascular diseases. A meta-analysis shows that a combination of folic acid and vitamin B6 reduces the risk of stroke more effectively than other B vitamin combinations containing vitamin B12. A combination of B vitamins, including 2 mg of folic acid, 25 mg of vitamin B6, and 500 mg of vitamin B12, has been used daily for 3 to 4 years.
Posologie
Orally
25 mg
4 - years
Adults
Attention Deficit Disorders ✪✪✪✪✪
Some clinical research shows that taking high doses of vitamin B6 (pyridoxine) orally could improve symptoms in children with attention deficit hyperactivity disorder, who have low blood serotonin levels. A dose of 300 mg of vitamin B6 has been used.
Posologie
Orally
300 mg
Children
Cancer ✪✪✪✪✪
Demographic research has revealed that a higher dietary intake of vitamin B6 is associated with a 22% reduction in cancer risk, including esophageal, pancreatic, gastric, colorectal, and breast cancer. However, it is unknown if vitamin B6 contributes to reducing cancer risk in patients at risk. In fact, a meta-analysis of 9 clinical studies shows that taking vitamin B6 for 2 to 7.3 years, in combination with vitamin B12 and folate, does not reduce cancer risk in patients with cardiovascular or chronic kidney diseases.
Posologie
Orally
1.6 - 25 mg
Adults
Properties
Essential
Vitamin B6 is necessary for amino acid metabolism. It also plays a role in carbohydrate and lipid metabolism. In the body, vitamin B6 is converted into pyridoxal phosphate, a coenzyme for a wide variety of metabolic reactions. These reactions include the transamination of amino acids, the conversion of tryptophan to niacin, the synthesis of gamma-aminobutyric acid (GABA) in the central nervous system, the metabolism of serotonin, norepinephrine, and dopamine, the metabolism of polyunsaturated fatty acids and phospholipids, and the synthesis of the heme component of hemoglobin. Vitamin B6 thus contributes to normal energy metabolism, the normal functioning of the nervous system, the normal synthesis of cysteine, the normal metabolism of homocysteine, the reduction of fatigue, the normal metabolism of glycogen and proteins, normal mental functions, the formation of red blood cells, the normal functioning of the immune system, and the regulation of hormonal activity.
Usages associés
Cardiovascular
Vitamin B6 is a cofactor for enzymes involved in one of the two pathways of homocysteine metabolism, which is a marker of cardiovascular diseases. Indeed, high levels of homocysteine can cause damage to vascular endothelial cells, increased oxidation, and arterial deposition of low-density lipoproteins (LDL), increased platelet adherence, and activation of the coagulation cascade. The trans-sulfuration of homocysteine to form cystathionine is catalyzed by cystathionine beta-synthase, which depends on vitamin B6. This pathway is mainly active after ingesting a methionine load (i.e., after a meal). Therefore, vitamin B6 deficiencies impair this pathway, thereby increasing post-methionine homocysteine levels. Vitamin B6 supplements can lower homocysteine levels after methionine ingestion. Moreover, clinical and animal research suggests that vitamin B6 may lower blood pressure.
Usages associés
Anti-inflammatory
Decreased concentrations of vitamin B6 are associated with increased plasma levels of C-reactive protein (CRP) (CRP is an indicator of inflammation).
Usages associés
Antioxidant
Vitamin B6 (pyridoxine) exerts certain antioxidant activities by trapping free radicals.
Usages associés
Neurological
Pyridoxine is necessary for the synthesis of many neurotransmitters, including serotonin, adrenaline, and noradrenaline. It is a cofactor of 5-hydroxytryptophan decarboxylase, an enzyme involved in one of the conversion steps from tryptophan to serotonin. Pyridoxine is also necessary for tyrosine carboxylase, which converts tyrosine into dopamine, adrenaline, and noradrenaline. Vitamin B6 deficiency is associated with mood impairment and other psychological disorders. In attention deficit hyperactivity disorder (ADHD), some children may have low serotonin levels, although this is controversial. It is thought that vitamin B6 may increase serotonin levels and improve symptoms in some children with low serotonin levels. Some researchers believe that vitamin B6 supplementation may also be helpful with dysphoric mood (labile mood) as it increases serotonin and GABA production, but the evidence remains insufficient.
Usages associés
Anticancer
In vitro and in vivo experiments have found antitumor action of vitamin B6 on several cell lines, including breast and pituitary cells.
Usages associés
Safety dosage
Adult from 18 years: 1.6 mg - 25 mg
Orally, vitamin B6 is safe even at doses higher than the recommended dietary allowances. However, long-term doses exceeding 1g/day (or total doses of 1000g or more) carry risks.
Child from 1 to 3 years old: 0.6 mg - 5 mg
Infant up to 12 months: 0.3 mg
Child from 4 to 6 years old: 0.7 mg - 7 mg
Child from 7 to 10 years: 1 mg - 10 mg
Child from 11 to 14 years: 1.4 mg - 15 mg
Child from 15 to 17 years: 1.6 mg - 20 mg
Interactions
Médicaments
Amiodarone: moderate interaction
Amiodarone is an antiarrhythmic medication. Research suggests that vitamin B6 (pyridoxine) may exacerbate the photosensitivity induced by this medication. Other research suggests a protective effect instead.
Antihypertensive: moderate interaction
Clinical and animal studies suggest that vitamin B6 (pyridoxine) can lower systolic blood pressure in hypertensive patients. Therefore, it may increase the risk of hypotension when combined with antihypertensive medications.
Anticonvulsants: moderate interaction
Research suggests that 200 mg/day of vitamin B6 (pyridoxine) can reduce plasma levels of phenobarbital and phenytoin, probably by increasing their metabolism. It is unknown if lower doses have this effect. The combination of high doses of pyridoxine with phenobarbital and phenytoin should be avoided.
Cycloserine: moderate interaction
Cycloserine interacts with pyridoxal phosphate to form inactive hydrazones, which inhibit pyridoxal kinase and increase excretion of vitamin B6 in the urine. This loss likely contributes to the neurotoxicity and seizures associated with cycloserine. Vitamin B6 supplementation is recommended for individuals taking cycloserine.
Hydralazine: moderate interaction
Hydralazine may cause vitamin B6 deficiency in some individuals, probably by forming an inactive complex with pyridoxal phosphate, resulting in an inactive hydrazine excreted in the urine. Supplementation is necessary for individuals treated with hydralazine who develop early signs of peripheral neuropathy, such as paresthesia, numbness, and tingling.
Isoniazid: moderate interaction
Isoniazid interacts with vitamin B6 to form an inactive hydrazine, which inhibits pyridoxal kinase and increases excretion of vitamin B6 in the urine. This interaction is rare with a dose of 5 mg/kg/day of isoniazid. Higher doses of isoniazid may require vitamin B6 supplementation, especially in individuals with a history of seizures or other risk factors for neuropathies, including malnutrition, uremia, diabetes, alcoholism, or liver disease.
Penicillamine: moderate interaction
Penicillamine inhibits the activity of vitamin B6, possibly by forming an inactive complex with pyridoxal phosphate, which explains the peripheral and optic neuropathy associated with the drug. Vitamin B6 supplementation may be necessary.
Plantes ou autres actifs
Hypotensive: moderate interaction
Vitamin B6 (pyridoxine) has a hypotensive effect. Consequently, combining it with other herbs and supplements with the same effect might worsen hypotension. Such supplements and herbs include green chiretta, cat's claw, casein peptides, coenzyme Q10, fish oil, L-arginine, lycium, nettle, theanine, and others.
Precautions
Pregnant woman: use with caution
The maximum chronic daily intake defined by EFSA during pregnancy is 25 mg per day.
Breastfeeding woman: use with caution
The maximum chronic daily intake defined by EFSA during breastfeeding is 25 mg per day.
