Vitamin B-6, a water-soluble B vitamin found in poultry, fish, dairy products, legumes and some vegetables and whole grains, plays an important role in carbohydrate, protein and fat metabolism, nervous system function and eye, hair and skin health. No evidence shows that vitamin B-6 from food has adverse health effects, but high oral doses of vitamin B-6 in dietary supplements can pose health risks. A dose of 500 mg far exceeds the tolerable upper intake level for vitamin B-6 in supplements set by the Institute of Medicine.
Tolerable Upper Intake Level
Based on evidence that high doses of vitamin B-6 in supplements, also known as pyridoxine, can cause sensory neuropathy, dermatological lesions and other adverse effects, the Institute of Medicine established a tolerable upper intake level, or UL, for this nutrient. Adults ages 19 and older should not have more than 100 mg of vitamin B-6 as pyridoxine per day. Children ages 1 to 3 should not have more than 30 mg per day, children ages 4 to 8 should not have more than 40 mg per day, children ages 9 to 13 should not have more than 60 mg per day and adolescents ages 14 to 18 should not have more than 80 mg per day. Pregnant and lactating women should not have more than 80 mg per day.
Potential Side Effects
Doses of vitamin B-6 as high as 200 mg can cause dangerous side effects, including loss of sensation in your legs, loss of balance and other neurological problems, according to the University of Maryland Medical Center. These problems do not continue permanently, however, and discontinuing use of B-6 supplements usually enables recovery within half a year. In rare cases, vitamin B-6 supplements have caused allergic skin reactions. B-6 supplements may also cause loss of appetite, nausea, abdominal pain and increased sensitivity to sunlight.
Possible Interactions
Vitamin B-6 can have negative interactions with some medications. Vitamin B-6 and other B vitamins can interfere with the antibiotic tetracycline, so avoid taking B-6 at the same time as tetracycline. B-6 supplements may reduce the effectiveness of phenytoin, a medication used to treat seizures, and levodopa, a medication used to treat Parkinson's disease, according to the University of Maryland Medical Center.
Recommended B-6 Intake
Adult men and women ages 19 to 50 should get 1.3 mg of vitamin B-6 per day, adult women ages 51 and older should get 1.5 mg per day and adult men ages 51 and older should get 1.7 mg per day, according to the National Institutes of Health Office of Dietary Supplements. Pregnant women should get 1.9 mg of vitamin B-6 per day, and lactating women should get 2 mg. A healthy diet rich in fruits, vegetables and whole grains should provide sufficient vitamin B-6.
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