More and more people are presenting with symptoms linked to high levels of vitamin B6, pathologists say, while the supplement industry goes unpoliced, and products continue to proliferate on the shelves.
When Australia’s Simon Bogemann’s hand began cramping around the steering wheel in a claw position on his daily commute, he began to worry.
Bogemann, then 43, was also getting pins and needles in his feet and fingers every night in bed, and while sitting down during short lunch breaks at work, reports The Guardian.
His GP put it down to a lack of magnesium and recommended a supplement, in addition to the multivitamin he was taking for a chronic condition.
Bogemann was unaware that both capsules contained added vitamin B6, too much of which could lead to the symptoms he was experiencing – a type of nerve damage known as peripheral neuropathy.
A blood test recommended by his dietician showed his levels of B6 were 36 times the recommended range.
The wellness industry’s marketing of over-the-counter vitamins is leading to an increase in the number of people presenting with peripheral neuropathy linked to excessive vitamin B6 in their blood, Australia’s peak body for pathologists has warned.
Dr David Kanowski, a chemical pathologist in Brisbane, said most people are unaware they are consuming too much of the vitamin.
Bogemann certainly had no idea: “You buy an over-the-counter supplement, you just think that it’s going to be good for you, not bad for you.”
He said it has been a challenge to change his multivitamin to a product without B6.
“One thing that I have learned is that B6 seems to be added, for some reason, to a lot of over-the-counter supplements.” It is also in some energy drinks, breakfast cereals, and protein and weight loss shakes.
Magnesium tablets, commonly recommended for cramp relief, often contain B6 because it can assist magnesium absorption. But a person who takes two magnesium tablets a day could consume more than 120mg of B6, far exceeding the recommended dietary intake for adults in Australia of 1.3mg to 2mg a day.
It was previously believed that peripheral neuropathy was caused by doses of hundreds of milligrams taken over periods of 12 months or more but cases have been known to occur at levels as low as 21mg.
The initial symptoms include numbness and pins and needles in the feet, which can spread up the legs. Muscle cramps and pain may be felt in the arms and hands.
In 2020, the Therapeutic Goods Administration released a safety advisory warning. Two years later, still concerned about a lack of awareness, the TGA lowered the limit at which products must display a warning label, from 50mg of B6 down to 10mg – and banned products with more than 100mg.
Nevertheless, cases have continued to rise. Between January 2020 and October 2024 the TGA received 81 adverse event reports of peripheral neuropathy associated with medicines containing a vitamin B6 ingredient, with most of them reported in the past two years.
Kanowski said advertising on social and other media promoted the idea that taking more vitamins was good for health.
“It’s understood that if you want to counteract bad habits, like smoking or drinking too much, perhaps that can be counterbalanced with vitamins,” he said.
Kanowski said the TGA has been “fairly hands off” unless toxins are in a product.
Fiona Sammut, a dietician in Victoria, said it was a big ask to expect consumers to read and interpret “tiny font” disclaimers and formulations.
People who see claims that vitamins will “boost their energy” may take several supplements thinking they are harmless, she said.
While foods are commonly fortified with vitamins for “specific evidence-based reasons”, such as vitamin B1 fortified bread, Sammut said there was no similar reason for B6 fortification because there wasn’t a high incidence of vitamin B6 deficiency.
Most people get enough B6 in their diets from foods including fish, non-citrus fruits and starchy vegetables, and high intakes of B6 from natural food sources have not been reported to cause adverse effects.
In most cases, once B6 levels return to normal, peripheral neuropathy will slowly improve within six to 12 months but in some severe cases it can be irreversible.
Professor Matthew Kiernan, the chief executive of Neuroscience Australia, has described a case he saw in his clinical practice of a 40-year-old patient who was worried he had motor neurone disease before the doctor linked the gym enthusiast’s symptoms to excessive vitamin B6 intake from the supplements he consumed as part of his fitness programme.
Kiernan, who diagnosed more patients with peripheral neuropathy after his article on the case was published in the Medical Journal of Australia, believes there should be limits on the number of supplements people can buy because they are unnecessary for those eating a balanced diet.
“None of this is policed,” he said. “So, if you go down to the chemist and go down the vitamin aisle, they’re all there. You can get a whole shopping trolley full of them.”
See more from MedicalBrief archives:
Adverse effects of non-prescribed vitamins and supplements intake
Increase in liver injury linked to herbal and dietary supplements — Australian study
Concern over vitamins added to drinks