Vitamin B6: benefits, dosage, contraindications
Other name(s)
Pyridoxine, pyridoxamine, pyridoxal
Scientific name(s)
Pyridoxal-5'-Phosphate, Pyridoxine
Family or group:
Vitamins
Indications
Méthodologie de notation
EFSA approval.
Vitamin B6 deficiency ✪✪✪✪✪
Vitamin B6 deficiency is rare, leading to seborrhea (excessive secretion of sebum by the sebaceous glands), glossitis, a pellagroid erythema, polyneuropathy and even depression with manic episodes. It may be due to iatrogenic causes (treatment with isoniazid or D-penicillamine) or occur following pregnancy. In cases of vitamin B6 deficiency in adults, the dose used is 2.5 to 25 mg per day for three weeks, then continue a maintenance dose of 1.5 to 2.5 mg per day.
Posologie
Oral
2.5 - 25 mg
Adults
Anemia ✪✪✪✪✪
Sideroblastic anemias are anemias related to iron utilization, characterized by inadequate use of iron by the bone marrow for heme synthesis despite adequate or increased iron stores. Sideroblastic anemias may be acquired or congenital. Acquired sideroblastic anemias can be due, among other causes, to a vitamin B6 deficiency. The most common congenital sideroblastic anemia is an X-linked form caused by heterozygous germline mutations in the ALAS2 gene (a gene involved in heme biosynthesis). Vitamin B6 (pyridoxine) is an essential cofactor for the enzyme produced by ALAS2, so 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 decreased to 30 to 50 mg per day if the response is adequate.
Posologie
Oral
200 - 600 mg
Adults
Fatigue ✪✪✪✪✪
A0the European health authorities (EFSA, European Food Safety Authority and the European Commission) have concluded that products containing vitamin B6 can claim to contribute to normal energy metabolism and to the reduction of fatigue.
Posologie
Orally
1.6 - 25 mg
Adults
Emotional balance ✪✪✪✪✪
Pyridoxine is necessary for the synthesis of many neurotransmitters, including serotonin, epinephrine and norepinephrine. It is a cofactor of 5-hydroxytryptophan decarboxylase, which is an enzyme involved in one of the steps converting tryptophan to serotonin. Pyridoxine is also necessary for tyrosine carboxylase, which converts tyrosine into dopamine, epinephrine and norepinephrine. Pyridoxine deficiency is significantly associated with increased depression, fatigue, mood disturbances, and other psychological disorders.
Posologie
Orally
1.6 - 25 mg
Adults
Hyperhomocysteinemia ✪✪✪✪✪
Oral vitamin B6 (pyridoxine), alone or in combination with folic acid, is effective in treating postprandial hyperhomocysteinemia. Daily intake of 50 to 200 mg of pyridoxine reduces postprandial homocysteine levels by 32% to 35%. However, vitamin B6 appears to reduce homocysteine concentrations in patients who are deficient in folic acid and vitamin B12, and this occurs in combination with folic acid and vitamin B12 supplements. Pyridoxine has no effect on fasting homocysteine levels.
Posologie
Oral
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 hyperhomocysteinemia in patients with premature arterial disease and their relatives.
Homocysteine and coronary atherosclerosis.
AMD ✪✪✪✪✪
A large-scale clinical study in women over 40 years old with a history of cardiovascular disease or with cardiovascular risk factors showed that daily intake of 50 mg of vitamin B6 (pyridoxine), in combination with 1000 mcg of vitamin B12 (cyanocobalamin) and 2500 mcg of folic acid, for an average of 7.3 years, significantly reduced the risk of developing age-related macular degeneration (AMD) compared with placebo,nn
Posologie
Oral
50 mg
Women
Synergies
Kidney stone ✪✪✪✪✪
Most kidney stones are composed of calcium oxalate, and a high urinary oxalate level is associated with a high risk of developing kidney stones. Vitamin B6 appears to decrease urinary oxalate excretion in some patients. Indeed, in patients with type I primary hyperoxaluria, vitamin B6 (pyridoxine) appears to reduce stone formation by shifting the degradation of the precursor of oxalic acid, glyoxylic acid, toward glycine. In patients with type I primary hyperoxaluria, vitamin B6 (pyridoxine) has been used at doses of 25 to 500 mg per day.nn
Posologie
Oral
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 administration of vitamin B6, typically at a dose of 25 mg every 8 hours for 3 to 4 days, reduces nausea and vomiting during pregnancy. "The American College of Obstetricians and Gynecologists" considers pyridoxine a first-line treatment for nausea and vomiting of pregnancy. However, it is unclear whether pyridoxine is the most effective option for managing pregnancy-induced nausea and vomiting. Some studies suggest pyridoxine is more effective for severe nausea than for mild to moderate nausea. A lower dose of pyridoxine, 10 mg every eight hours, improves nausea but does not appear to significantly improve vomiting during pregnancy.
Posologie
By mouth
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 vitamin B6 (pyridoxine) intake can improve symptoms of premenstrual syndrome (PMS) such as pain, breast tenderness and depression in some patients. The combination of 50 mg pyridoxine and 200 mg magnesium oxide per day appears to relieve anxiety and other PMS-related symptoms.
Posologie
Oral
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 more than 44,000 patients shows that B vitamin supplementation slightly reduces the relative risk of stroke (cerebrovascular accident) by 10% compared with placebo in patients at risk or with a history of cardiovascular disease. However, it is not yet known which specific combination of B vitamins is optimal for reducing stroke risk in patients with cardiovascular disease. One meta-analysis shows that a combination of folic acid and vitamin B6 reduces stroke risk more effectively than other B vitamin combinations that include vitamin B12. A combination of B vitamins, including 2 mg of folic acid, 25 mg of vitamin B6, and 500 mg of vitamin B12, taken daily for 3 to 4 years, was used.
Posologie
Oral
25 mg
4 - years
Adults
Attention deficit disorders ✪✪✪✪✪
Some clinical research shows that taking high doses of vitamin B6 (pyridoxine) orally may improve symptoms in children with attention deficit hyperactivity disorder who have low blood serotonin levels. nnA dose of 300 mg of vitamin B6 was used.nn
Posologie
Oral
300 mg
Children
Cancer ✪✪✪✪✪
Epidemiological research has found that a higher dietary intake of vitamin B6 is associated with a 22% reduction in cancer risk, including esophageal cancer, pancreatic cancer, stomach cancer, colorectal cancer, and breast cancer. However, it is not known whether vitamin B6 helps reduce cancer risk in at-risk patients. Indeed, 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.nn
Posologie
Oral
1.6 - 25 mg
Adults
Properties
Essential
Vitamin B6 is necessary for the metabolism of amino acids. It also plays a role in the metabolism of carbohydrates and lipids. 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.nnVitamin B6 thus contributes to normal energy metabolism, the normal functioning of the nervous system, the normal synthesis of cysteine and the normal metabolism of homocysteine, to the reduction of fatigue, to the normal metabolism of glycogen and proteins, to normal mental function, to the formation of red blood cells, to the normal functioning of the immune system, and to the regulation of hormonal activity.nn
Usages associés
Cardiovascular
Vitamin B6 is a cofactor for the enzymes involved in one of the two pathways of homocysteine metabolism, which is a marker of cardiovascular disease. Indeed, elevated homocysteine levels can cause damage to vascular endothelial cells, increased oxidation and arterial deposition of low-density lipoproteins (LDL), increased platelet adhesion, and activation of the coagulation cascade. The transsulfuration of homocysteine to form cystathionine is catalyzed by cystathionine beta-synthase, which depends on vitamin B6. This pathway is mainly active after a methionine load (that is, after a meal). Therefore, vitamin B6 deficiencies impair this pathway, 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 vitamin B6 concentrations are associated with increased plasma levels of C-reactive protein (CRP) (CRP is an indicator of inflammation).
Usages associés
Antioxidant
Vitamin B6 (pyridoxine) exerts some antioxidant activity by scavenging 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, which is an enzyme involved in one of the steps converting tryptophan to serotonin. Pyridoxine is also necessary for tyrosine carboxylase, which converts tyrosine into dopamine, adrenaline and noradrenaline. A vitamin B6 deficiency is associated with mood disturbance and other psychological disorders. In attention deficit hyperactivity disorder (ADHD), some children may have low serotonin levels. However, this is controversial. It is thought that vitamin B6 may increase serotonin levels and may improve symptoms in some children with low serotonin levels. Some researchers think that vitamin B6 supplementation may also be useful in dysphoric mood (labile mood) because it increases the production of serotonin and GABA, but the evidence is still insufficient.
Usages associés
Anticancer
In vitro and in vivo experiments have found an antitumor effect of vitamin B6 on a number of cell lines, including breast and pituitary cells.
Usages associés
Safe dosage
Adults aged 18 years and older: 1.6 mg - 25 mg
When taken orally, vitamin B6 is safe even at doses higher than the recommended nutritional intakes. However, long-term doses that exceed 1 g/day (or total doses of 1000 g or more) are risky.nn
Child aged 1 to 3 years: 0.6 mg - 5 mg
Infant up to 12 months: 0.3 mg
Child 4 to 6 years: 0.7 mg - 7 mg
Child 7 to 10 years: 1 mg - 10 mg
Child 11 to 14 years: 1.4 mg - 15 mg
Child 15 to 17 years: 1.6 mg - 20 mg
Interactions
Médicaments
Amiodarone: moderate interaction
Amiodarone is an antiarrhythmic drug. Research suggests that vitamin B6 (pyridoxine) may exacerbate photosensitivity induced by this drug. Other research suggests a protective effect.
Antihypertensive: moderate interaction
Clinical and animal studies suggest that vitamin B6 (pyridoxine) may 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 whether 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 the 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 people taking cycloserine.
Hydralazine: moderate interaction
Hydralazine can cause vitamin B6 deficiency in some individuals, probably by forming an inactive complex with pyridoxal phosphate and producing an inactive hydrazine that is excreted in the urine. Supplementation is necessary for patients treated with hydralazine who develop early signs of peripheral neuropathy, such as paresthesias, numbness, and tingling.
Isoniazid: moderate interaction
Isoniazid interacts with vitamin B6 to form an inactive hydrazine, which inhibits pyridoxal kinase and increases urinary excretion of vitamin B6. This interaction is rare at an isoniazid dose of 5 mg/kg/day. Higher doses of isoniazid may require vitamin B6 supplementation, particularly in people with a history of seizures or other risk factors for neuropathies, including malnutrition, uremia, diabetes, alcoholism, or liver disease.
Penicillamine: moderate interaction
Penicillamine inhibits vitamin B6 activity, 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
Antihypertensive: moderate interaction
Vitamin B6 (pyridoxine) has a hypotensive effect. Therefore, combining it with other herbs and supplements that have the same effect may worsen hypotension. These supplements and herbs include: green chiretta (Andrographis), cat's claw, casein peptides, coenzyme Q10, fish oil, L-arginine, Lycium, nettle, theanine, and others.
Precautions
Pregnant women: use with caution
The maximum chronic daily intake defined by EFSA during pregnancy is 25 mg per day.
Breastfeeding women: use with caution
The maximum chronic daily intake defined by EFSA during breastfeeding is 25 mg per day.
