asxan.ai Agents Hub

Vitamin B6

Evidence Fact Sheet

Vitamin B6 (pyridoxine/pyridoxal-5-phosphate) is an essential water-soluble vitamin and coenzyme for over 150 enzymes in amino-acid, neurotransmitter and heme metabolism. Randomized evidence is mixed: it shows benefit for premenstrual symptoms but null effects on homocysteine-driven vascular events and cognition. Typical doses 1.4-25 mg/day.

Also known as: Pyridoxine · Pyridoxal · Pyridoxamine · Pyridoxal-5-phosphate · P5P · PLP · Pyridoxine hydrochloride · Vitamina B6

Overview

Vitamin B6 is an essential water-soluble B-vitamin whose active coenzyme form, pyridoxal-5-phosphate (PLP), is required by more than 150 enzymes involved in amino-acid metabolism, neurotransmitter synthesis (serotonin, dopamine, GABA), heme biosynthesis for red blood cells, and the transsulfuration pathway that converts homocysteine to cysteine. Common supplemental doses range from about 1.4 to 25 mg/day, with the US IOM Tolerable Upper Intake Level set at 100 mg/day and the more conservative EFSA UL at 25 mg/day, reflecting concern over sensory neuropathy with chronic very-high-dose use. Regulatory status is well established: the EU (EFSA Reg 432/2012) authorizes ten Article 13(1) function claims (energy metabolism, nervous system, homocysteine metabolism, red blood cell formation, immune function, reduction of tiredness/fatigue, hormonal regulation and others), ANVISA authorizes analogous functional claims in Brazil, and in the US it carries DSHEA structure/function claims with no SSA disease claim. This page reports research findings in studied populations, not disease treatment.

Mechanism of Action

Active form pyridoxal-5-phosphate (PLP) serves as coenzyme for >150 enzymes including aminotransferases, decarboxylases, and synthases · Catalyzes transsulfuration pathway (cystathionine beta-synthase + cystathionine gamma-lyase) converting homocysteine to cysteine and glutathione precursor · Coenzyme for delta-aminolevulinic acid (ALA) synthase, rate-limiting step in heme biosynthesis for red blood cell hemoglobin · Coenzyme for glycogen phosphorylase regulating muscle glycogenolysis during exercise · Required for neurotransmitter synthesis: serotonin (from 5-HTP), dopamine (from L-DOPA), GABA (from glutamate), norepinephrine

Body systems: Endocrine & Metabolic · CNS · METABOLISM

Evidence-Based Benefits

Each benefit below is anchored to a specific PubMed-indexed study. Effect sizes, sample sizes, and p-values are reported as published; no values are inferred. Honest negatives and null results are kept alongside the positive findings, and disease-research populations are described as such — Vitamin B6 is not characterized as a treatment for any disease.

Premenstrual Syndrome (Symptom Relief)

Meta-analysis supported
  • OR 2.32overall PMS symptoms vs placebo
  • 1.95 to 2.5495% CI

A systematic review of randomized placebo-controlled trials found that women taking vitamin B6 were more than twice as likely to report improvement in overall premenstrual symptoms versus placebo, with a separate benefit signal for premenstrual depressive symptoms. The authors stressed the evidence came from low-quality trials, so the result is suggestive rather than definitive.

Reported effect: OR 2.32 (95% CI 1.95 to 2.54) for improvement in overall premenstrual symptoms; OR 1.69 (1.39 to 2.06) for depressive symptoms (4 trials, 541 patients)

“Odds ratio relative to placebo for an improvement in overall premenstrual symptoms was 2.32 (95% confidence interval 1.95 to 2.54). Odds ratio relative to placebo for an improvement in depressive symptoms was 1.69 (1.39 to 2.06) from four trials representing 541 patients.”

Source: PMID 10334745 · Wyatt 1999 · BMJ

Homocysteine Lowering (Additional Effect of B6)

Null / no benefit Meta-analysis supported
  • mean 16.5 mg/dayB6 dose · no added effect
  • 12 trials · 1,114randomized trials · people

In the classic meta-analysis of homocysteine-lowering trials, folic acid produced the large reduction in blood homocysteine and vitamin B12 added a small further reduction, but vitamin B6 (mean 16.5 mg/day) did not have a significant additional effect on fasting homocysteine. This is an honest negative that nuances B6's authorized 'homocysteine metabolism' claim: B6 supports the pathway but does not itself lower fasting homocysteine on top of folate and B12.

Reported effect: Vitamin B6 (mean 16.5 mg daily) did not have a significant additional effect on fasting homocysteine (folic acid reduced homocysteine 25% [95% CI 23-28%]; B12 added 7% [3-10%])

“Vitamin B-6 (mean 16.5 mg daily) did not have a significant additional effect.”

Source: PMID 9569395 · Homocysteine Lowering Trialists' Collaboration 1998 · BMJ

Stroke / Vascular Event Prevention (B6 + B12 + Folate)

Null / no benefit RCT supported
  • RR 0.91composite vascular endpoint
  • 0.82 to 1.00 · p=0.0595% CI · borderline

In the large VITATOPS secondary-prevention trial in patients with recent stroke or TIA, a B-vitamin combination including B6 did not significantly reduce the composite of stroke, myocardial infarction, or vascular death versus placebo (the result was borderline at p=0.05). Despite the homocysteine rationale, B-vitamin supplementation did not clearly prevent vascular events.

Reported effect: Primary composite endpoint: 616/4089 (15%) on B vitamins vs 678/4075 (17%) on placebo; RR 0.91 (95% CI 0.82 to 1.00, p=0.05); absolute risk reduction 1.56% (-0.01 to 3.16)

“616 (15%) patients assigned to B vitamins and 678 (17%) assigned to placebo reached the primary endpoint (risk ratio [RR] 0.91, 95% CI 0.82 to 1.00, p=0.05; absolute risk reduction 1.56%, -0.01 to 3.16).”

Source: PMID 20688574 · VITATOPS Trial Study Group 2010 · Lancet Neurol

Cognitive Performance (Homocysteine Lowering)

Null / no benefit RCT supported
  • 276healthy adults ≥65y

In a randomized controlled trial of healthy older adults, B6 + B12 + folate substantially lowered plasma homocysteine but produced no improvement in cognitive performance versus placebo. The authors explicitly concluded the data do not support the idea that lowering homocysteine with B vitamins improves cognition.

Reported effect: Homocysteine fell 4.36 micromol/L more in the vitamin group than placebo (P<0.001), but no significant difference in cognitive performance between groups; n=276 adults aged >=65y

“The results of this trial do not support the hypothesis that homocysteine lowering with B vitamins improves cognitive performance.”

Source: PMID 16807413 · McMahon 2006 · N Engl J Med

Nausea and Vomiting of Pregnancy (vs Ginger)

Meta-analysis supported
  • OR 1.239ginger vs B6 · NS
  • 0.495 to 3.10295% CI · overlaps 1

A meta-analysis comparing ginger, vitamin B6, and placebo for nausea and vomiting of pregnancy found no significant difference between ginger and vitamin B6 across general symptoms, nausea severity, or vomiting. The overlapping confidence intervals indicate B6 performed comparably to ginger, supporting B6 as a studied option for pregnancy nausea.

Reported effect: Ginger vs B6: general NVP symptoms OR 1.239 (95% CI 0.495-3.102); nausea severity SMD 0.199 (-0.102 to 0.500); vomiting SMD 0.331 (-0.145 to 0.808) — no significant difference

“ginger intervention has no significant effect on improving general symptom of NVP [OR = 1.239, 95% CI = (0.495, 3.102), I2 = 57.3%], relieving severity of nausea [SMD = 0.199, 95% CI = (-0.102, 0.500), I2 = 65.7%], reducing vomiting [SMD = 0.331, 95% CI = (-0.145, 0.808), I2 = 85.9%], compared with vitamin B6.”

Source: PMID 31937153 · Hu 2022 · J Matern Fetal Neonatal Med

Cancer Risk (Dietary B6 / PLP Status)

Meta-analysis supported
  • RR 0.78dietary B6 · all cancers
  • RR 0.66high PLP · all cancers
  • 9 RCTs · nulltrials show no protection

A field synopsis and meta-analysis found that higher dietary vitamin B6 intake and higher blood PLP levels were associated with lower cancer risk in observational studies. Critically, randomized controlled trials did NOT support a protective effect of B6 supplementation against cancer, so the observational inverse association should not be read as evidence that B6 supplements prevent cancer.

Reported effect: Dietary B6 vs all cancers RR 0.78 (95% CI 0.73-0.84); high PLP RR 0.66 (0.58-0.76); but 9 RCTs did not support a protective effect (graded low level)

“High intake of dietary (food only) vitamin B6 was statistically significantly associated with lower risk of all cancers (relative risk [RR] = 0.78, 95% CI = 0.73 to 0.84) ... Findings from RCTs did not support a protective effect of vitamin B6 against cancer, although this evidence was graded as low level.”

Source: PMID 28376200 · Mocellin 2017 · J Natl Cancer Inst

Dosage (research context · not a recommendation)

US IOM RDA: 1.3 mg/day adults 19-50y, 1.5 mg/day women 51+, 1.7 mg/day men 51+ (1.9 mg/day pregnancy, 2.0 mg/day lactation). EFSA NDA AI: 1.6 mg/day adult men, 1.6 mg/day adult women (1.8 mg/day pregnancy, 1.7 mg/day lactation). EFSA NRV (labelling): 1.4 mg. Common supplemental doses: 1.4-25 mg/day. US IOM Tolerable Upper Intake Level (UL): 100 mg/day adults. EFSA UL: 25 mg/day adults. Higher doses (50-100 mg/day) in clinical use for hyperhomocysteinemia or premenstrual symptoms must be time-limited under clinical supervision.

Regulatory Status · 4 Markets

US · FDA
United States (FDA): NO 21 CFR Part 101 Subpart E SSA health claim exists for vitamin B6. Vitamin B6 is not among the 12 SSA-authorized nutrient-disease pairs. No FDA Qualified Health Claim (QHC) under 21 CFR 101.93 has been authorized for vitamin B6 either. Vitamin B6 is regulated as an essential nutrient under 21 CFR 101.9 (Nutrition Facts) with a Daily Value of 1.7 mg, and may bear DSHEA structure/function claims under 21 CFR 101.93 (e.g., "supports nervous system function", "supports energy metabolism") provided the disclaimer "This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease." is included.
EU · EFSA
European Union (EFSA / Reg 432/2012): Ten authorized Article 13(1) function health claims for vitamin B6 in the Annex to Commission Regulation (EU) No 432/2012 (CELEX:32012R0432), covering cysteine synthesis, energy-yielding metabolism, nervous system functioning, homocysteine metabolism, protein and glycogen metabolism, psychological function, red blood cell formation, immune system function, reduction of tiredness and fatigue, and regulation of hormonal activity. All ten share the standard condition: claim may be used only for food which is at least a source of vitamin B6 per the SOURCE OF reference in the Annex to Regulation (EC) No 1924/2006 (>=15% NRV per 100 g/100 mL or per portion; NRV = 1.4 mg per Regulation (EU) No 1169/2011 Annex XIII). No Article 14 disease-risk-reduction claim authorized for vitamin B6.
CN · China
Established nutrient — SAMR-permitted vitamin B6 source (pyridoxine hydrochloride) under GB 14880 food-fortifier and GB 2760 standards; usable in health foods and general food fortification (NRV 1.4 mg/day; adult RNI 1.4 mg/day; UL 60 mg/day). P5P form on the permitted list is unconfirmed.
BR · ANVISA
Brasil (ANVISA): A vitamina B6 (piridoxina) é constituinte autorizado para suplementos alimentares conforme Instrução Normativa DC/ANVISA IN nº 28/2018 (com atualizações em IN 76/2020 e seguintes), Anexos I/II (constituintes), III/IV (limites mínimos e máximos) e V (alegações autorizadas). As alegações funcionais autorizadas seguem o padrão verbatim oficial "A vitamina B6 auxilia ..." cobrindo metabolismo de proteínas / carboidratos / gorduras, formação de células vermelhas do sangue, síntese de cisteína, funcionamento do sistema imune, sistema nervoso, função psicológica, redução do cansaço e fadiga, e regulação da atividade hormonal.

Authorized Claims

ANVISA — “A vitamina B6 auxilia no metabolismo de proteínas, carboidratos e gorduras.” (IN 28/2018 Anexo V)

Safety

Vitamin B6 is generally well-tolerated at supplemental doses up to the UL. Chronic high-dose B6 supplementation (>200 mg/day for months to years) is associated with sensory peripheral neuropathy that is usually reversible upon discontinuation but may be persistent in severe cases. The EFSA UL of 25 mg/day is more conservative than the US UL of 100 mg/day and reflects this neurotoxicity concern. Drug interactions: B6 reduces effectiveness of levodopa (when taken without carbidopa); may reduce phenytoin and phenobarbital serum levels; potentiates effects of altretamine. Patients on isoniazid, hydralazine, cycloserine, penicillamine, or oral contraceptives may have increased B6 requirements. Pregnancy/lactation: stay within RDA unless clinically directed; pyridoxine has been used safely for nausea of pregnancy at 10-25 mg doses.

Goals: cognitive-support · longevity-stack · heart-health

Lifestyles: senior-60-plus

References

PubMed-indexed citations anchoring the benefit findings above. Effect sizes are reported as published.

  1. PMID 10334745 · Wyatt 1999 · BMJ — Premenstrual Syndrome (Symptom Relief)
  2. PMID 9569395 · Homocysteine Lowering Trialists' Collaboration 1998 · BMJ — Homocysteine Lowering (Additional Effect of B6)
  3. PMID 20688574 · VITATOPS Trial Study Group 2010 · Lancet Neurol — Stroke / Vascular Event Prevention (B6 + B12 + Folate)
  4. PMID 16807413 · McMahon 2006 · N Engl J Med — Cognitive Performance (Homocysteine Lowering)
  5. PMID 31937153 · Hu 2022 · J Matern Fetal Neonatal Med — Nausea and Vomiting of Pregnancy (vs Ginger)
  6. PMID 28376200 · Mocellin 2017 · J Natl Cancer Inst — Cancer Risk (Dietary B6 / PLP Status)

Frequently Asked Questions

1. Does vitamin B6 actually help with premenstrual syndrome (PMS)?

A systematic review of randomized placebo-controlled trials (Wyatt 1999, PMID 10334745) found women taking vitamin B6 were more than twice as likely to report improvement in overall premenstrual symptoms (OR 2.32, 95% CI 1.95 to 2.54), with a separate signal for premenstrual depressive symptoms (OR 1.69). The authors emphasized the included trials were low quality, so the finding is suggestive rather than conclusive. This page reports research findings, not treatment advice.

2. If B6 supports homocysteine metabolism, does it lower blood homocysteine?

Not on its own. In the classic meta-analysis of homocysteine-lowering trials (PMID 9569395), folic acid drove the large reduction and B12 added a small further effect, but vitamin B6 at a mean of 16.5 mg/day did not have a significant additional effect on fasting homocysteine. B6 is a coenzyme in the transsulfuration pathway, which is why it carries an authorized 'homocysteine metabolism' function claim, but the trial data show it does not by itself reduce fasting homocysteine beyond folate and B12.

3. Is high-dose vitamin B6 safe?

B6 is generally well tolerated up to the upper intake limits, but chronic very-high-dose use is the main safety concern. Common supplemental doses fall in the roughly 1.4-25 mg/day range; the US IOM Tolerable Upper Intake Level is 100 mg/day while EFSA sets a more conservative 25 mg/day. The conservative EFSA limit reflects the risk of sensory peripheral neuropathy with prolonged intake of very high doses, which is usually reversible on stopping. This is general evidence reporting, not personal dosing guidance.

Last evidence review: 2026-06-05

← Evidence library

Ask Agent Axor