Here's proof that too much of a good thing may not be such a good thing after all: Taken in doses exceeding 250 mg daily, vitamin B6 (pyridoxine) can have a toxic effect on your nervous system (Encyclopedia of Natural Medicine [Prima] by Michael Murray, N.D., and Joseph Pizzorno, N.D.). In fact, some studies have shown that doses of 50 mg daily can cause neuropathy.
According to Tucson, Arizona-based nutritionist Melissa Diane Smith, co-author with Ann Louise Gittleman of Why Am I Always So Tired? (HarperSanFrancisco), megadoses of vitamin B6 can cause nerve damage, numbness or tingling in the body when taken in the absence of supporting nutrients such as the other B vitamins. Unless prescribed as a single dose by a health care provider, Smith explains, B6 should be taken with other B vitamins, and it's best to limit the supplemental amount you take to no more than 100 to 150 mg per day.
"Higher amounts of vitamin B6 can be therapeutic in treating or preventing a number of health disorders, including hormone disturbances, heart disease, diabetes, carpal tunnel syndrome, weakened immunity and copper excess," says Smith, "but it's wise to seek the advice of a nutritionally oriented health professional before taking excess B6 to address any of these health issues."
— Debra Bokur