Vitamin B6

Vitamin B6 is the only B-vitamin authorised under EU law to carry the claim that it contributes to the regulation of hormonal activity.^[2] That single claim is the reason B6 sits in every phase of nōuxx Cycle Routine. It also covers nine other functions across mood, energy, nervous system function and red blood cell formation.^[2]

If she has read that B6 helps with PMS, this page covers which form is used, how much she needs and what the research shows. It also covers the dose ceiling that matters for any woman taking B6 long term.

Forms of vitamin B6

Vitamin B6 exists in three natural forms. Pyridoxine is found in plants. Pyridoxal and pyridoxamine are found in animal products. All three convert in the liver to the active coenzyme pyridoxal-5-phosphate (P-5-P), which the body uses for over 140 enzyme reactions.^[1]

Pyridoxine hydrochloride (HCl) is the most studied form in supplements. It is stable. It is well absorbed in the small intestine. The liver phosphorylates it to P-5-P on demand. This is the form used in nōuxx Cycle Routine across all three phases.^[1]

Pyridoxal-5-phosphate (P-5-P) is marketed as a bioactive form that skips the liver conversion step. In practice P-5-P taken orally is dephosphorylated in the gut wall before absorption then re-phosphorylated in the liver. It ends up at the same destination as pyridoxine HCl. For women with normal liver function there is no measurable benefit.^[1] nōuxx uses pyridoxine HCl because the evidence base is broader.

How much you need

The European Food Safety Authority sets the adequate intake for vitamin B6 at 1.6 mg per day for adult women. Pregnancy raises that to 1.8 mg. The EU Nutrient Reference Value used on supplement labels is 1.4 mg.^[1]

Vitamin B6 is the one B-vitamin where more is not better. Chronic high-dose supplementation can cause sensory peripheral neuropathy. Symptoms include tingling, numbness or burning in the hands and feet. The mechanism appears to involve inhibition of pyridoxal kinase in sensory neurons.^[4] A 2023 systematic review confirmed pyridoxine-induced neuropathy is almost always sensory and axonal. Symptoms typically improve after stopping supplementation.^[5]

EFSA sets the tolerable upper intake level at 12 mg per day for adults from all sources. The 3 mg dose in nōuxx Cycle Routine sits well below that ceiling. Cases of neuropathy are typically reported at intakes of 50 mg or more daily over months or years.^[8]

The science on women's health

PMS and premenstrual mood

Vitamin B6 has one of the strongest evidence bases of any nutrient for premenstrual symptoms. A 2025 systematic review of 31 randomised controlled trials in over 3,200 women looked at nutritional interventions for the psychological symptoms of PMS. Vitamin B6 was one of three nutrients with consistent positive effects on premenstrual mood. The other two were calcium and zinc.^[3]

The biology fits. P-5-P is a required cofactor for the enzymes that synthesise serotonin from tryptophan and GABA from glutamate. Both pathways are implicated in premenstrual mood. P-5-P is also a cofactor for oestrogen metabolism. This is the mechanism behind the EU-authorised hormonal regulation claim.^[1]

Energy, nervous system and homocysteine

Vitamin B6 sits on the energy-yielding pathways that convert food into ATP. It also works alongside folate and B12 to clear homocysteine, a metabolite associated with cardiovascular risk when it accumulates. A 2024 systematic review and meta-analysis reported that higher intakes of B6, B12 and folate were associated with lower cardiovascular disease risk in the general population.^[7] For women this becomes more relevant after menopause.

EU authorised health claims

Under EU law, vitamin B6 is officially authorised to carry the following health claims:

• Vitamin B6 contributes to the regulation of hormonal activity
• Vitamin B6 contributes to the reduction of tiredness and fatigue
• Vitamin B6 contributes to normal energy-yielding metabolism
• Vitamin B6 contributes to normal functioning of the nervous system
• Vitamin B6 contributes to normal psychological function
• Vitamin B6 contributes to the normal function of the immune system
• Vitamin B6 contributes to normal protein and glycogen metabolism
• Vitamin B6 contributes to normal homocysteine metabolism
• Vitamin B6 contributes to normal cysteine synthesis
• Vitamin B6 contributes to normal formation of red blood cells^[2]

References

[1] National Institutes of Health, Office of Dietary Supplements. Vitamin B6: Fact Sheet for Health Professionals. ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional

[2] Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. Official Journal of the European Union, 25 May 2012. eur-lex.europa.eu

[3] Robinson J, Ferreira A, Iacovou M, Kellow NJ. Effect of nutritional interventions on the psychological symptoms of premenstrual syndrome in women of reproductive age: a systematic review of randomized controlled trials. Nutrition Reviews 2025;83(2):280-306. doi.org/10.1093/nutrit/nuae043

[4] Hadtstein F, Vrolijk M. Vitamin B-6-induced neuropathy: exploring the mechanisms of pyridoxine toxicity. Advances in Nutrition 2021;12(5):1911-1929. doi.org/10.1093/advances/nmab033

[5] Muhamad R, Akrivaki A, Papagiannopoulou G, Zavridis P, Zis P. The role of vitamin B6 in peripheral neuropathy: a systematic review. Nutrients 2023;15(13):2823. doi.org/10.3390/nu15132823

[6] He L, Fan Y, Hu Y, et al. The potential hazards of high doses of vitamin B6 in treating nausea and vomiting in pregnancy: a systematic review. International Journal of Gynaecology and Obstetrics 2025;169(1):38-50. doi.org/10.1002/ijgo.16032

[7] Miao Y, Guo Y, Chen Y, Lin Y, Lu Y, Guo Q. The effect of B-vitamins on the prevention and treatment of cardiovascular diseases: a systematic review and meta-analysis. Nutrition Reviews 2024;82(10):1386-1401. doi.org/10.1093/nutrit/nuad127

[8] Calderon-Ospina CA, Nava-Mesa MO, Paez-Hurtado AM. Update on safety profiles of vitamins B1, B6, and B12: a narrative review. Therapeutics and Clinical Risk Management 2020;16:1275-1288. doi.org/10.2147/TCRM.S274122