Vitamin B6

Medically reviewed by Prof. Giorgi Pkhakadze, MD, MPH, PhD — GMJ Editorial Board

What is Vitamin B6?

Vitamin B6, scientifically known as pyridoxine, is a water-soluble vitamin that plays essential roles in protein metabolism, cognitive development, and immune function. It exists in several forms, including pyridoxine (found in plant foods), pyridoxal (found in animal products), and pyridoxamine. The body converts these forms into pyridoxal 5′-phosphate (PLP), the active coenzyme form that participates in over 100 enzymatic reactions.

As a water-soluble vitamin, B6 cannot be stored in large amounts in the body and must be regularly obtained through diet or supplementation. The Recommended Dietary Allowance (RDA) for adults is 1.3-1.7 mg daily, with the upper limit (UL) set at 100 mg per day due to potential neurotoxicity at higher doses.

Health benefits & uses

Strong evidence: Vitamin B6 supplementation effectively treats pyridoxine-responsive seizures in infants and pyridoxine-dependent epilepsy. It also helps reduce elevated homocysteine levels when combined with folate and B12, potentially supporting cardiovascular health.

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Moderate evidence: Research suggests B6 may help alleviate morning sickness during pregnancy, with some studies showing reduced nausea and vomiting. It may also support cognitive function in older adults and help maintain normal immune system function.

Limited evidence: Some studies suggest potential benefits for premenstrual syndrome (PMS) symptoms, carpal tunnel syndrome, and mood regulation, though more research is needed to establish definitive therapeutic effects.

How it works

Vitamin B6 functions primarily as the coenzyme pyridoxal 5′-phosphate (PLP), which is crucial for amino acid metabolism. It facilitates the conversion of one amino acid to another through transamination reactions and supports the synthesis of neurotransmitters including serotonin, dopamine, and GABA. These neurotransmitters regulate mood, sleep, and cognitive function.

B6 also plays a vital role in glycogen breakdown, releasing glucose for energy, and in the synthesis of hemoglobin, the oxygen-carrying protein in red blood cells. Additionally, it supports immune function by promoting lymphocyte proliferation and interleukin-2 production, key components of the adaptive immune response.

Dosage

For general health maintenance, the RDA provides adequate intake: 1.3 mg daily for adults under 51, and 1.7 mg for men and 1.5 mg for women over 51. Pregnant women require 1.9 mg daily, while breastfeeding women need 2.0 mg daily.

Therapeutic doses vary by condition but typically range from 10-50 mg daily under healthcare supervision. For morning sickness, studies have used 10-25 mg every 8 hours. The upper limit of 100 mg daily should not be exceeded long-term due to neurotoxicity risk. Always consult a healthcare provider before using therapeutic doses, especially for specific medical conditions.

Food sources

Excellent sources of vitamin B6 include chickpeas (1 cup provides 1.1 mg), beef liver (3 oz provides 0.9 mg), and yellowfin tuna (3 oz provides 0.9 mg). Good sources include salmon, chicken breast, and fortified breakfast cereals.

Plant-based sources include potatoes with skin (1 medium provides 0.4 mg), bananas (1 medium provides 0.4 mg), and bulgur wheat. Nuts, seeds, and many vegetables contribute smaller amounts. Note that vitamin B6 in plant foods is generally less bioavailable than in animal products, though a varied diet typically provides adequate amounts.

Safety & side effects

Vitamin B6 is generally safe when taken within recommended amounts. However, chronic intake above 100 mg daily can cause peripheral neuropathy, characterized by numbness and tingling in hands and feet. This condition is typically reversible when excessive intake stops, though recovery may take months to years.

Some individuals may experience mild side effects even at lower therapeutic doses, including nausea, headache, or drowsiness. Very high doses (above 200 mg daily) have been associated with photosensitivity and skin lesions. Pregnant women should not exceed therapeutic doses without medical supervision.

Interactions

Several medications can interfere with vitamin B6 status. Isoniazid (tuberculosis treatment) can cause B6 deficiency and is often prescribed with B6 supplementation. Anti-seizure medications like phenytoin and carbamazepine may reduce B6 levels and can have their effectiveness altered by high-dose B6 supplementation.

Levodopa’s effectiveness for Parkinson’s disease can be reduced by vitamin B6, though this interaction doesn’t occur with carbidopa-levodopa combinations. Some antibiotics and oral contraceptives may also affect B6 status. High-dose B6 supplementation may interfere with certain laboratory tests, potentially affecting results.

Who should be cautious

Individuals with kidney disease should use B6 supplements cautiously, as reduced kidney function can affect vitamin metabolism and excretion. People taking anti-seizure medications require medical supervision when using B6 supplements due to potential drug interactions.

Those with a history of peripheral neuropathy should avoid high-dose supplements unless medically indicated and monitored. Pregnant and breastfeeding women should not exceed recommended therapeutic doses without healthcare guidance. Anyone considering B6 supplementation for medical conditions should consult their healthcare provider first.

Frequently asked questions

Can vitamin B6 help with morning sickness?

Yes, studies suggest that vitamin B6 supplementation at 10-25 mg every 8 hours may help reduce nausea and vomiting during pregnancy. However, pregnant women should consult their healthcare provider before starting any supplementation regimen.

Is it safe to take B6 long-term?

Yes, when taken at recommended doses (under 100 mg daily), vitamin B6 is safe for long-term use. However, chronic intake above the upper limit of 100 mg daily can cause nerve damage, so higher therapeutic doses should only be used under medical supervision.

Can B6 improve mood and reduce PMS symptoms?

Some research suggests B6 may help with PMS symptoms and mood regulation due to its role in neurotransmitter synthesis. However, evidence is mixed, and more research is needed to establish definitive benefits for these conditions.

Do I need B6 supplements if I eat a balanced diet?

Most people following a varied, balanced diet get adequate B6 from food sources. Supplements may be beneficial for those with increased needs (pregnancy, certain medical conditions), dietary restrictions, or taking medications that interfere with B6 metabolism.

What’s the difference between different forms of B6?

Pyridoxine hydrochloride is the most common supplement form, while pyridoxal 5′-phosphate (P5P) is the active coenzyme form. Both are effective, though some people with certain genetic variations may better utilize P5P. For most people, standard pyridoxine is adequate and more cost-effective.