Vitamin B-6, also known as pyridoxine, is one of the B complex vitamins commonly found in meat, eggs, beans, vegetables and cereals. The B-complex vitamins play important roles maintaining the health of the eyes, hair, skin, liver and nervous system. Supplements containing vitamin B-6 and the other B vitamins are often used to treat a variety of health conditions, including heart disease and high cholesterol. While vitamin B-6 is generally safe and well-tolerated, taking very large doses may cause side effects, particularly affecting the nervous system. Liver damage as a side effect of vitamin B-6 has not been widely reported.
Toxicity
Unlike most other water-soluble vitamins, vitamin B-6 can accumulate to dangerously high levels in the body if large doses are taken for a long period of time. Cases of vitamin B-6 toxicity have only been reported as a result of taking vitamin B6 supplements; you are very unlikely to consume too much vitamin B-6 only from normal dietary intake. The Food and Nutrition Board of the Institute of Medicine has set a tolerable upper intake level of 100 mg per day for adults aged 19 years and older. The levels are smaller for adolescents and children younger than 19. The risk of toxicity is greatly increased when doses of 500 mg or more per day are taken, according to the Linus Pauling Institute at Oregon State University.
General Side Effects
Several general, non-specific side effects can result from taking too much vitamin B-6. Early symptoms of a vitamin B-6 overdose include upset stomach, loss of appetite, nausea and vomiting. Stomach or abdominal pain also occur. Sensitivity to sunlight and headache have also been reported. Additional possible side effects include fatigue and excess sleepiness.
Nerve Damage
Long-term intake of large amounts of vitamin B-6 can cause nerve damage, also known as neuropathy. Early signs of nerve damage often begin as a tingling sensation or numbness in the extremities such as the fingers and toes. As the nerve damage spreads, the tingling sensation or numbness often spreads up the arms or legs. Left untreated, the nerve damage induced by vitamin B-6 can lead to loss of coordination, loss of balance and difficulty walking. The symptoms of nerve damage often disappear within six months after intake of vitamin B-6 is stopped or reduced to safe levels.
Drug Interactions
Vitamin B-6 can also possibly interact with several medications. It causes your body to increase the rate at which it breaks down the anti-seizure medication, phenytoin. Taking vitamin B-6 at the same time as phenytoin can increase your risk of seizures. Vitamin B-6 can also increase how quickly your body breaks down phenobarbital and levodopa. Additionally, because vitamin B-6 increases your sensitivity to sunlight, taking it with other medications that also increase sun sensitivity, such as amiodarone, can increase the risk of severe sunburn and blistering.
References
- MedlinePlus; Pyridoxine (Vitamin B6); Nov. 19, 2010
- University of Maryland Medical Center; Vitamin B6 (Pyridoxine ); Steven D. Ehrlich, NMD; June, 18, 2009
- Linus Pauling Institute at Oregon State University; Vitamin B6; Nov. 2007
- Office of Dietary Supplements of the National Institutes of Health: Vitamin B6
