Historical View

The research that revealed vitamin B6 is a neurotoxin was published in the early ’40s. Unna and Antopol are responsible for the original studies that resulted in toxicity among animals with very large doses of vitamin B6. Research through the decades continued with the assumption that only large doses caused toxicity.

This large dose toxicity assumption was challenged by London researchers, Dalton & Dalton. In 1985, Dalton & Dalton first observed that 40% of women who had been taking vitamin supplements for premenstrual syndrome AND had plasma levels above normal, showed signs of vitamin B6 toxicity. Their signs included tingling and shooting pains, burning/prickling of limbs, clumsiness, loss of full control of bodily movements and mouth numbness. In the 1987 follow up study with 172 women, Dalton & Dalton found that vitamin B6 toxicity was possible with B6 supplementation levels as low as 50 mg. Their research was ridiculed and ignored at the time.

In a follow-up newspaper article debating the toxicity of vitamin B6, Arnold Beckett with the Vitamin B6 Scientific Task Group stated, “The unrepresentative Dalton study has been deemed worthless by the medical and scientific community. If Dalton’s findings were even partially valid there would be a veritable epidemic of vitamin B6 neurotoxicity”. THERE WOULD BE A VERITABLE EPIDEMIC OF VITAMIN B6 NEUROTOXICITY. Remember these words.

In the year 2000, the European Commission’s Health & Consumer Protection Directorate General published an opinion on the “Tolerable Upper Intake of Level of Vitamin B6”. This commission reviewed the literature. They did not ignore the Dalton and Dalton study. It was recommended by this committee that the upper tolerable limit for the European Union be set at 25 mg for adults.

The following is quoted directly from this European Commission’s opinion paper: “The Food and Nutrition Board of the Institute of Medicine (FNB, 1998) in the USA recently set an upper limit of 100 mg/day for adults. That report did not use the study of Dalton and Dalton (1987) to establish the NOAEL because they considered that the weakness of the study and the inconsistency of the results with the weight of the evidence pertaining to the safety of higher doses of pyridoxine ruled out the use of these data to base on upper level. The report highlighted a number of methodological weaknesses in the study, but in reality, many of these apply also to the other studies available on pyridoxine.” The report then states that the studies used to establish the upper tolerable limit of vitamin B6 in the United States did not have the duration of treatment and/or the quantity of subjects that were used in the Dalton and Dalton research. In other words, the Food and Nutrition Board for the USA did not use the Dalton and Dalton research due to the weakness of the study when in fact, the other research used was weaker than the Dalton and Dalton study.

In the twenty-five-plus years following the Dalton & Dalton study, vitamin B6 became the wonder vitamin of the period. As research money went towards proving the viability of the new wonder vitamin, most B6 toxicity research came to a halt.

A 2014 Google of vitamin B6 toxicity had very slim results. The two main pages at the time were a member discussion on an old MedHelp page and the no longer available side effects and warnings page from the Mayo Clinic. Below is quoted directly from the 2014 to 2016 list of side effects for vitamin B6 on the Mayo Clinic website.

“Vitamin B6 may cause abnormal heart rhythms, acne, allergic reactions, breast enlargement or soreness, changes in folic acid levels, decreased muscle tone, drowsiness or sedation, feeling of a lump in the throat, feeling of tingling in the skin, headache, heartburn, loss of appetite, nausea, rash, recurrence of ulcerative colitis (an inflammatory bowel condition), stomach discomfort or pain, sun sensitivity, vomiting and worsened asthma”.

“Vitamin B6 may cause low blood pressure. Caution is advised in people with blood pressure disorders or in those taking drugs or herbs and supplements that lower blood pressure”.

“Vitamin B6 may affect blood sugar levels. Caution is advised in people with diabetes or low blood sugar, and in those taking drugs, herbs or supplements that affect blood sugar.”

“Vitamin B6 may cause the risk of bleeding. Caution is advised in people with bleeding disorders or taking drugs that may increase the risk of bleeding.”

“Use cautiously in people who have heart conditions or stomach or intestine conditions.”


During the same time, Mayo Clinic graded the usefulness of vitamin B6. Unfortunately, that page was not printed out. We remember that B6 was given a grade of an “A” for nutrition and two more categories. There was one category that was a grade of “B”. The rest of the grades were “C’s” and worse. The summary of the studies done in each category that was graded a C or worse showed that there was not enough evidence to suggest that B6 would help these health conditions. This information showed that the decades of research to prove B6 was a wonder vitamin didn’t reveal this wonder vitamin status.

Although we did not print out the Mayo Clinic effectiveness information, MedlinePlus has created a page that rates vitamin B6’s effectiveness. Again, B6 is stated to be very effective for three situations (Mayo Clinic’s “A”). There is one situation in like effective (Mayo Clinic’s “B”). There are three situations that which it is possibly effective (Mayo Clinic’s “C”). The rest of the situations are possibly ineffective (Mayo Clinic’s “D”). It has not proven to be the wonder vitamin.

In the United States, daily dietary intake of vitamin B6 is approximately 1.9 mg/day (Morris, MS et al, 2003 – 2004). Recommended daily allowance of B6 is 1.3 mg for most adults with men and women over 50 taking 1.7 mg and 1.5 mg respectively. Most Americans are getting more B6 in their diet than the recommended daily amount. Although the research states that B6 neurotoxicity from food is not possible, there is no long-term research to support that statement.

In a Netherlands study published in May of 2018, van Hunsel, et al., searched the Netherlands adverse drug reaction database for cases using vitamin B6 with subsequent neuropathic complaints. The amount of B6 varied between 1.4 and 100 mg per tablet. This summary discloses adverse effects from vitamin B6 with only 1.4 mg. This is the first research that reveals B6 toxicity can happen with just recommended daily allowance.

Although the research is just now showing that adverse reactions can happen with just 1.4 mg of vitamin B6, the B6T Smart Understanding Vitamin B6 Toxicity Facebook group has known this since 2015. As of date, about 1/3 of our members have vitamin B6 toxicity from food alone. They are toxic from a high protein (high B6) diet. Many are toxic on a multivitamin with just RDA.

The changes in our society in the past sixty years contributed to the rise of vitamin B6 toxicity. Cereal fortification, including added B6, started in the ’40s. Kid’s multivitamins and prenatal vitamins became a must. As we moved away from junk food, into wholesome, healthy, superfoods, we moved into foods higher in vitamin B6. The increased chance of toxicity was created with the popularity of energy drinks. Our love affair with TV, video games and the internet meant less daily exercise which meant the B6 in our muscle storage was not emptying. Finally, our communal ignorance about proper hydration including warnings from society to stay away from those very elements we need to stay hydrated helped create the dehydrating events that cause B6 to stay in our blood.

For more information, also see: Vitamin B6

Any unlinked research can be found in our Index of Sources

Read more on the blog: Vitamin B6 Toxicity: Why Now?











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