Pyridoxine is one of the chemical names for vitamin B-6, a vital nutrient. Vitamin B-6 is involved with protein metabolism, red cell metabolism, functioning of your immune and nervous systems and synthesis of neurotransmitters in your brain. Vitamin B-6 is found in fruits, vegetables whole grains and dairy foods. Pyridoxine is added to enrich many processed foods and is the form of vitamin B-6 in most supplements. Pyridoxine toxicity may cause health complications.
Neuropathy
An excess of pyridoxine is toxic and may result in damage to your nerves in your arms and legs called neuropathy. The excess usually comes from overconsumption of nutritional supplements that contain pyridoxine. The upper tolerable intake level for pyridoxine is 100 mg per day for adults. The risk for neuropathy increases as the supplement dosage or total daily intake of pyridoxine exceeds 100 mg per day. When dosage falls below 100 mg, the symptoms of neuropathy may be reversible. Research by Martijn Katan Ph.D. published in "Nederlands Tijdschrift Voor Geneeskunde" in 2005 reports that intake of pyridoxine at doses of 1000 mg per day or more is toxic and causes neuropathy; this dosage is about 800 times the daily intake from foods. The research also reports cases of two patients with neurotoxicity from taking 24 mg and 40 mg of pyridoxine per day. Research by Hans-Jurgen Gdynia, M.D., published in "Neuromuscular Disorders" in 2008 reports a case that is to the researchers' knowledge the highest dosage of vitamin B-6 administered to humans over a long period of time that is published in medical literature. The research found that a white Caucasian patient who consumed 9.6 g of pyridoxine per day experienced severe neuropathy that caused muscle weakness and movement impairment.
Allergic Reactions and Other Side Effects
Pyridoxine is safe at doses below 100 mg for most adults and children. However, some people are sensitive to vitamin B-6 and may have problems at lower doses and should avoid excessive doses. Side effects from pyridoxine, especially at toxic levels, may include allergic reactions, photosensitivity of skin, acne, abdominal pain, nausea, vomiting, loss of appetite, headaches, abnormalities of liver enzymes, tiredness, seizures, respiratory distress, difficulty breathing and breast soreness and enlargement.
Kidney Damage
Patients with kidney disease may require pyridoxine supplementation because they excrete larger than normal amounts of vitamin B-6. Research by Seymour Levine Ph.D. published in "Food and Chemical Toxicology" in 2002 found that patients with kidney disease who take pyridoxine supplements to prevent a deficiency of vitamin B-6, may increase risk of pyridoxine-induced neuropathy. The research demonstrates that pyridoxine given to rats with kidney dysfunction causes a five- to 10-fold increase in susceptibility to pyridoxine-induced neuropathy. The research concludes by suggesting caution in prescribing pyridoxine to patients with kidney disease who probably will need to take the vitamin supplement daily for many years.
References
- National Institutes of Health Office of Dietary Supplements: Vitamin B6
- "Nederlands Tijdschrift Voor Geneeskunde"; How Much Vitamin B6 Is Toxic?; Katan, M.B.; Nov 12 2005
- "Neuromuscular Disorders"; Severe Sensorimotor Neuropathy after Intake of Highest Dosages of Vitamin B6; Gdynia, H.J.; Feb 2008
- MayoClinic.com: Vitamin B6
- "Food and Chemical Toxicology"; Pyridoxine (Vitamin B6) Toxicity: Enhancement by Uremia in Rats; Levine, S.; Oct 2002
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