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Vitamin B6 (Pyridoxine)

Vitamin B6 (Pyridoxine) Functions

Vitamin B6 is a water soluble vitamin, an essential nutrient involved in [1]:

  • Synthesis of glucose from glycogen (glycogenolysis) and from amino acids (gluconeogenesis)
  • Synthesis of amino acids and thus proteins, including the formation of myelin that surrounds the nerves
  • Synthesis of vitamin B3 (niacin) from the amino acid tryptophan
  • Synthesis of the chemical messengers (neurotransmitters), such as serotonin, norepinephrine, dopamine and GABA
  • Synthesis of hemoglobin
  • Development of lymphocytes and thus proper function of the immune system
  • Reference: [1]

Vitamin B6 forms: pyridoxine, pyridoxine 5′-phosphate (PNP), pyridoxal, pyridoxal 5′-phosphate (PLP), pyridoxamine, pyridoxamine 5′-phosphate [1].

The name origin: pyrid- from pyridine (cyclic organic compound); ox- from hydroxyl groups (OH); -ine from the amino group (NH2).

Vitamin B6 Daily Requirements

The Recommended Dietary Allowance (RDA) for vitamin B6 for adults 19-50 years of age is 1.3 mg/day, for men 51 years and older 1.7 mg/day, for women 51 years and older 1.5 mg/day, during pregnancy 1.9 mg/day and during breastfeeding 2.0 mg/day [1].

Foods Rich in Vitamin B6

  • PLANT FOODS: fortified ready-to-eat cereals, sweet/potatoes, yam, taro, grains (rice brown, rice, corn, wheat and others), prunes, bananas, avocado, jackfruit, legumes, spinach, pistachios, sunflower seeds
  • ANIMAL FOODS: red meat, poultry, liver, fish
  • Human breast milk contains sufficient amount of vitamin B6 for infants 0-6 months of age.
  • References: [1,2]

Freezing and drying does not significantly affect the vitamin B6 content of foods but cooking can reduce it by 50% [3].

Vitamin B6 Deficiency: Causes, Symptoms

Vitamin B6 deficiency is rare and may be caused by:

  • Low vitamin B6 intake in starvation, chronic alcoholism
  • Chronic kidney disease
  • Malabsorption in Crohn’s and celiac disease
  • Rheumatoid arthritis
  • Homocystinuria (a genetic disease)
  • Medications: theophylline (for asthma), isoniazid and cycloserine (for tuberculosis), penicillamine (a metal chelator), L-dopa (for Parkinson’s disease)

Symptoms of vitamin B6 deficiency may include ulcers in the mouth and corners of the lips, seborrheic dermatitis, eczema, acne, pale skin and fatigue (from microcytic anemia), anxiety, depression, confusion, seizures and tingling in the hands and feet.

Individuals with vitamin B6 deficiency may be at increased risk for heart disease and stroke (due to increased blood homocysteine level) and infections (due to impaired production of lymphocytes and thus low immunity).

Vitamin B6 deficiency usually occurs in combination with deficiency of other vitamins from the B-complex.

References: [1,4]

Vitamin B6 Supplements

Without prescription (over-the-counter):

  • Pyridoxal phosphate
  • Pyridoxine hydrochloride as part of vitamin B complex and multivitamin supplements

Available OTC forms: tablets (regular, extended release, enteric coated), sublingual tablets, capsules and solutions

By prescription:

  • Pyridoxine hydrochloride intramuscular or intravenous injection (in severe deficiency)
  • Pyridoxine hydrochloride nasal spray

Possible Vitamin B6 Supplements Benefits

Vitamin B6 is EFFECTIVE in [5]:

  • Prevention and treatment of pyridoxine deficiency
  • Treatment of pyridoxine-responsive sideroblastic anemia, but not other types of sideroblastic anemia [7]
  • Treatment of certain inborn types of seizures in infants (pyridoxine-dependent epilepsy) [8]

Vitamin B6 is POSSIBLY EFFECTIVE in:

  • Reducing high blood levels of homocysteine [4,9]. There is insuficient evidence about high homocysteine levels as a risk factor for coronary heart disease.
  • Kidney stones in primary hyperoxaluria type 1 (vitamin B6 alone or in combination with magnesium) but less likely in kidney stones from other causes [1,10]
  • Movement disorders (tardive dyskinesia) in people taking medicines for mental disorders [11,12]
  • Treatment of homocystinuria (in some individuals) [20]

Vitamin B6 is POSSIBLY INEFFECTIVE or there is INSUFFICIENT EVIDENCE about its effectiveness in prevention or treatment of acne and other skin conditions, alcohol hangover [18], anxiety, age-related macular degeneration (AMD), allergies, Alzheimer’s disease, arthritis, asthma, attention deficit-hyperactivity disorder (ADHD), autism, bladder infections (cystitis), blood clots (thrombosis), breast milk reduction, breast tenderness, cancer, carpal tunnel syndrome, convulsions due to fever, depression, diabetes mellitus, dizziness, Down syndrome, eye infections, infertility, kidney stones, leg cramps at night, Lyme disease, McArdle’s disease, menstrual cramps, migraine headaches, morning sickness (nausea and vomiting during pregnancy; hyperemesis gravidarum) [13,19], motion sickness, movement disorders (tardive dyskinesia, hyperkinesis, chorea), muscle cramps, nerve pain caused by diabetes or drugs, osteoporosis, premenstrual syndrome (PMS), preeclampsia (high blood pressure in pregnancy), preterm birth, re-blockage of blood vessels after angioplasty, seizures (epilepsy), sickle cell anemia, stroke, improving memory in old people, increasing appetite or boosting the immune system or improving cognitive function [1,4,5,13,14].

Vitamin B6 Safety: Side Effects, Toxicity, Dangers

The Tolerable Upper Intake Limit (UL) for vitamin B6–the dose that should not cause side effects–is 100 mg/day [1].

Vitamin B6 supplements in doses higher than 200 mg/day may cause nausea, vomiting, stomach pain, loss of appetite, headache, pains, photosensitivity (burns after exposure to moderate sunlight), numbness or tingling in the arms and legs, clumsiness (unstable gait) and sleepiness [5,15,17]. Allergic reactions to vitamin B6 are possible. Harmful effects of high doses of vitamin B6 from food has not been observed [4,16].

Overdose

Chronic vitamin B6 intake by mouth or injections in large doses greater than 1 g/day may cause nerve damage (neuropathy) with permanent sensory loss [4,15], loss of coordination (ataxia) and drop of blood folate levels [4,4,16].

During Pregnancy

Vitamin B6 is a pregnancy category C drug, which means, adverse effects in human fetuses have not been observed so far, but insufficient studies have been done so they can not be ruled out [15]. If you intend to use pyridoxine during pregnancy or breastfeeding, speak with your doctor.

Vitamin B6 Interactions With Drugs

  • Drugs that may decrease the vitamin B6 effectiveness: theophylline, isoniazid, cycloserine, penicillamine, L-dopa [4,5].
  • High doses of vitamin B6 may decrease the effectiveness of anticonvulsants phenobarbital and phenytoin (and eventually resulting in convulsions), and L-dopa [5].
  • Taking vitamin B6 supplements along with amiodarone may increase the risk of sunburn [5].

  1. Vitamin B6  Linus Pauling Institute
  2. List of foods high in vitamin B6  US Department of Agriculture
  3. Nutritional Effects of Food Processing  SELF NutritionData
  4. Vitamin B6  National Institutes of Health, Office of Dietary Supplements
  5. Pyridoxine (Vitamin B6)  Medline Plus
  6. Koren G et al, 2010, Effectiveness of delayed-release doxylamine and pyridoxine for nausea and vomiting of pregnancy: a randomized placebo controlled trial  PubMed
  7. Baumann Kreuziger LM, 2011, Lack of efficacy of pyridoxine (vitamin B6) treatment in acquired idiopathic sideroblastic anaemia, including refractory anaemia with ring sideroblasts  PubMed
  8. Gospe SM, 2001, Pyridoxine-Dependent Epilepsy
  9. Dusitanond P et al, 2005, Homocysteine-Lowering Treatment With Folic Acid, Cobalamin, and Pyridoxine Does Not Reduce Blood Markers of Inflammation, Endothelial Dysfunction, or Hypercoagulability in Patients With Previous Transient Ischemic Attack or Stroke  Stroke
  10. Lorenz EZ et al, 2014, Sustained pyridoxine response in primary hyperoxaluria type 1 recipients of kidney alone transplant  PubMed
  11. DeVeaugh-Geiss J et al, 1978, High-dose pyridoxine in tardive dyskinesia  PubMed
  12. Lerver V et al, 2001, Vitamin B(6) in the treatment of tardive dyskinesia: a double-blind, placebo-controlled, crossover study  PubMed
  13. Thaver D et al, 2009, Pyridoxine (vitamin B6) supplementation in pregnancy  Cochrane
  14. Vitamin B6 (Pyridoxine), Evidence  Mayo Clinic
  15. Pyridoxine side effects  Drugs.com
  16. Pyridoxine hydrochloride injection, solution  DailyMed
  17. Pyridoxine  Medscape
  18. Wiese JG et al, 2000, The alcohol hangover  Annals of Internal Medicine
  19. Matthews A et al, 2010, Interventions for nausea and vomiting in early pregnancy  PubMed Central
  20. Homocystinuria/homocysteinemia treatment  Emedicine

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