The U.S. energy drink market is booming, with over $12 billion in sales and a 5.5% prevalence of consumption. Vitamin B6 toxicity is a known cause of peripheral neuropathy. The FDA % Daily Value for Vitamin B6 is 1.7 mg. After reviewing associations between B6 and neuropathy, the European Food Safety Authority set a tolerable upper limit of 12 mg/day for adults. However, the amount of vitamin B6 contained in one serving of popular energy drinks can be as high as 2,353% of the Daily Value or 333% of the tolerable upper limit. Labels instruct users to limit consumption to two servings per day, which would yield 4,706% of the Daily Value!

The International Society of Sports Nutrition states that patients with neurological conditions should consult with their physician prior to consuming energy drinks. Because there is only one PUBMED-indexed case report of neuropathic pain due to energy drinks, neurologists lack information about this causal relationship.

Seven cases of neuropathic pain occurred in patients consuming energy drinks. These included exacerbation of a remote critical illness polyneuropathy and a new onset of occipital neuralgia. The reference range for serum vitamin B6 is 2.1-21.7 ng/mL. Many of the patients had levels >100ng/mL. Symptoms significantly improved within 4 months of cessation of energy drinks.

Vitamin B6 content in energy drinks often exceeds the % Daily Value established by the FDA, as well as the tolerable upper limit determined by the European Food Safety Authority. Patients who develop new symptoms of neuropathy or exacerbations of previously existing neuropathy should be questioned about consumption of energy drinks and screened for vitamin B6 toxicity. Cessation of energy drinks resulted in improvements and resolution of symptoms.