My recent blood level test of B6 is 73 mcg per litre (73 ug/L), which is high. I took 1.25 grams of the vitamin over 2 days, which is too much. Then I stopped when I figured it out. Can this level of B6 cause neuropathic symptoms?
I actually took it because I sensed something that is somewhat similliar to PN. EMG/NCT is fine, so no Large-Fiber Neuropathy at least. Since symptoms began before I took the B6, and are also present after taking it and untill now, I can't tell if any side effects are actually present because of it. The blood test was taken 5 days after I took the vitamin, and 9 days have gone since.
Thank you.
Written by
ItsBurningMan
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I actually got neuropathic symptoms with low vitamin B6 and also high vitamin B6. Luckily I realised my problem quite quickly and the symptoms subsided when I stopped the B6 for a few months. I never buy a B Complex with massive doses of B6 now.
I never measured my B6. I started taking a high dose B Complex about 10 years ago and pain in my legs and feet started to disappear and eventually went completely after a few months. I carried on taking the high dose B Complex for quite a few more months. Eventually I started to get pain in my legs and feet again, although it didn't feel exactly the same as it did before.
I did some research and found out that Vitamin B6 is toxic in overdose. So I gave up the high dose B Complex and gradually the peripheral neuropathy started to disappear again and hasn't returned.
I didn't take a B Complex again for several years, but eventually I started to take a much better quality product (one of the ones frequently recommended on this forum from Igennus or Thorne Research) with a much lower dose of B6 than before, and have had no further issues.
The taking of B-complexes, and of just B6, has often been discussed here. I, along with several others, have pointed out that high doses of B6 should be avoided as they can cause neuropathy - one of the symptoms that it is sometimes taken to help relieve.
This paper, from 2017 has an explanation for this phenomenon.
What it doesn't do is give information about doses. It appears to say that, while pyridoxine can cause neuropathy, other forms of B6, such as pyridoxal-5'-phosphate, do not cause this issue.
1 Department of Pharmacology and Toxicology, Maastricht University, Maastricht, The Netherlands. Electronic address: m.vrolijk@maastrichtuniversity.nl.
2 Department of Pharmacology and Toxicology, Maastricht University, Maastricht, The Netherlands; Netherlands Food and Consumer Product Safety Authority (NVWA), Utrecht, The Netherlands.
3 National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands.
4 Department of Pharmacology and Toxicology, Maastricht University, Maastricht, The Netherlands.
Abstract
Vitamin B6 is a water-soluble vitamin that functions as a coenzyme in many reactions involved in amino acid, carbohydrates and lipid metabolism. Since 2014, >50 cases of sensory neuronal pain due to vitamin B6 supplementation were reported. Up to now, the mechanism of this toxicity is enigmatic and the contribution of the various B6 vitamers to this toxicity is largely unknown. In the present study, the neurotoxicity of the different forms of vitamin B6 is tested on SHSY5Y and CaCo-2 cells. Cells were exposed to pyridoxine, pyridoxamine, pyridoxal, pyridoxal-5-phosphate or pyridoxamine-5-phosphate for 24h, after which cell viability was measured using the MTT assay. The expression of Bax and caspase-8 was tested after the 24h exposure. The effect of the vitamers on two pyridoxal-5-phosphate dependent enzymes was also tested. Pyridoxine induced cell death in a concentration-dependent way in SHSY5Y cells. The other vitamers did not affect cell viability. Pyridoxine significantly increased the expression of Bax and caspase-8. Moreover, both pyridoxal-5-phosphate dependent enzymes were inhibited by pyridoxine. In conclusion, the present study indicates that the neuropathy observed after taking a relatively high dose of vitamin B6 supplements is due to pyridoxine. The inactive form pyridoxine competitively inhibits the active pyridoxal-5'-phosphate. Consequently, symptoms of vitamin B6 supplementation are similar to those of vitamin B6 deficiency.
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