Sept. 20, 2021 -- Vitamin B6, widely promoted and taken as a supplement, should carry a warning label about possible nerve problems, according to the CEO of a large contract research lab in Northern California.
And doses above 10 milligrams should be switched from over-the-counter to prescription status, says Ron Najafi, PhD, CEO of Emery Pharma, who filed a citizen's petition with the FDA on Friday. He wants the agency to regulate and revise industry guidance on high doses of over-the-counter vitamin B6, due to risks of severe toxic exposure that causes numbness and tingling of the hands and feet.
"What's the point of taking 100 milligrams or 50 milligrams?" Najafi says, pointing to a recommended daily amount that is 2 milligrams or less. Yet, he says, mega doses of 50 mg to 500 mg are widely available over the counter.
He suggests a warning label that says: "This medication may be dangerous when used in large amount or for a long time. Stop taking this medication if you experience tingling, burning, or numbness, and see your health care practitioner as soon as possible."
"This is a vitamin that about 30% of the population is taking," says Ana Najafi, PharmD, a co-author of the petition who’s on the staff at Emery Pharma. Supplement makers promote B6 for heart health, a healthy immune system, and a healthy nervous system.
Ron Najafi points to advice from the National Health Service in the United Kingdom that advises people not to take more than 10 mg of B6 daily.
Industry groups pushed back on Najafi’s petition, saying it is not necessary.
More on Vitamin B6 and How Much Is Enough
Vitamin B6, a water-soluble vitamin, is also found in foods like poultry, fish, potatoes, bananas, and fortified cereals. It helps with normal brain development and keeps the nervous system and immune system healthy.
Adults need 1.2 to 2.0 milligrams a day, depending on age and gender; the highest amount is recommended for pregnant or breastfeeding women. Two cups of chickpeas have 2.2 mg; a 3-ounce chicken breast has 0.5 mg.
Deficiency of vitamin B6 is more likely in people with kidney or autoimmune disease, in people who have trouble absorbing nutrients from foods, or in those who have alcohol dependence.
In the petition, Najafi lists the case history of a 63-year-old man who began taking 100 mg of vitamin B6 daily in July 2020. By May 2021, he had heat sensitivity, tingling in the hands and feet, and numbness in his hands. He also reported extreme thirst, facial flushing, and frequent urination.
Doctors did multiple tests, including checking for such conditions as type 2 diabetes and multiple sclerosis, and found all tests normal except the vitamin B6 level, which was 5 times the median normal range.
Even after stopping the supplement, symptoms continued for a month, then subsided but didn't disappear even by the end of September.
Another case history, reported in 2020 in the French medical journalLa Revue de Medecine Interne, described a 92-year-old woman who had used high levels of vitamin B6 supplements and had trouble walking due to nerve issues. Doctors said her use of too much vitamin B6 was the cause, finding blood levels about 6 times normal.
The researchers warn: "Vitamin B6 is contained in a number of over-the-counter drugs and vitamin supplements. It may cause severe neurological trouble in case of overdosage."
What Other Research Shows
In its review of the evidence, Mayo Clinic says B6, once promoted to prevent heart and blood vessel disease, doesn't seem to reduce those risks. It could help treat morning sickness during pregnancy, a genetic kind of anemia, and perhaps premenstrual syndrome (PMS).
Most of the evidence about toxicity, Najafi says, is from case reports. In a 2017 report in a toxicology journal, researchers said more than 50 cases of a sensory nerve pain due to vitamin B6 supplements were reported from 2014 to 2017.
The lowest dose reported to cause adverse effects is 50 mg, Najafi says in his petition, citing a 1987 study that he acknowledges has issues with methodology.
There is no need for a warning label on Vitamin B6, say spokespeople from two industry groups that issued statements in response to the petition.
"Vitamin B6 plays a role in numerous functions in the body and can be safely consumed from foods and dietary supplements," says Andrea Wong, PhD, a senior vice president at the Council for Responsible Nutrition. "The tolerable upper intake level for vitamin B6 is 100 mg in adults, based on the risk of sensory neuropathy; however, research indicates that sensory neuropathy usually develops at far higher doses. We encourage individuals to talk to their health care provider about what levels of vitamin B6 are appropriate to support their health."
In another statement, Jay Sirois, PhD, of the Consumer Healthcare Products Association, also cites the limit of 100 mg, set by the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine, and that side effects linked with B6 are ''likely the result of taking extremely high doses for extended periods of time.
"We've known for a long time that vitamin B6 excess can lead to numbness and tingling, but this is predominantly with supplements," says Connie Diekman, a registered dietitian and a food and nutrition consultant in St. Louis who is also a former president of the Academy of Nutrition and Dietetics. "You can't eat enough foods with B6 to get to a toxic level."
But with supplements, she says, ''if the consumption to excess occurs over time, it can go to that neuropathy."
"When you look at what they are saying [in the petition], I think it is very appropriate to ask that [federal officials] review the current body of evidence and dosage as it relates to toxicity."
But right now, "I'm not sure the body of evidence supports the need for a warning label yet."