High vitamin B6 doses over a long period could cause irreversible nerve damage

Mine only has 4.3 mg, that's definitely not right

Happened to me too. I had been consuming two energy drinks per day for a week or so and then my SO (who's addicted to vitamin supplements) gave me some multivitamins that I took just to be nice. Apparently that pushed me over the edge.

After one night and day of sweating profusely and feeling really bad, and me thinking I've cached a bug on my daily public commute, I didn't think about it any more, until days later when I began shedding the top layer of skin on my palms. Like, big flakes just started to fall off. Similar to what happens when you've had a severe sun burn.

Once that was over, any my palms were back to normal, it was then I noticed that compared to previously, my sense of touch wasn't what it used to be. Also, I noticed that I wasn't sweating as much any more. It was at this point I went to see my GP who confirmed elevated levels of B6 but didn't give any other diagnosis. This was two weeks later though and I was still sporadically consuming energy drinks, but it made me remember reading about B6 toxicity, so I began looking into it.

My own suspicion is that overconsumption of B6 damaged the nerve endings under my skin leading to a reduction in touch and the ability to sweat.

So now I live my life with about a 25 to 50% reduction (subjective) of my sense of touch. Plus I barely sweat any more (which has it's upsides). Before, I was an "easy sweater" and would begin to sweat if I walked a kilometer to the train station in the summer (20C or so), but now I can be out all day in 30+ weather (~90F) without as much as a drop of sweat.

I still sweat if I do actual prolonged physical exercise, like when I'm at the gym or exercise bike, but during daily life, not really any more. Also my hands are always dry and as a side effect quite slippery.

So yeah, stay clear of vitamin supplements and overconsumption of energy drink. I'm just happy it wasn't worse in the end, as I've read about many life changing cases of B6 toxicity.

Serious side effects from long term high dose vitamin B6 include peripheral neuropathy. Doses exceeding 500 to 1000 mg per day pose the greatest risk but prolonged intake of lower doses may also result in this side effect. The Therapeutic Goods Association of Australia has found that peripheral neuropathy can occur at doses of less than 50 mg.

In pregnant adult women, vitamin B6 is likely safe at a dose of up to 100 mg per day. In adolescent pregnancy, vitamin B6 is likely safe at a dose of up to 80 mg per day.

In lactating adult women, vitamin B6 is likely safe at a dose of up to 100 mg per day. In adolescents who are lactating, vitamin B6 is likely safe at a dose of up to 80 mg per day.

In children, vitamin B6 is likely safe at a daily dose of 30 mg (1-3 yrs), 40 mg (4-8 yrs), 60 mg (9-13 yrs) and 80 mg (14-18 yrs).

The likelihood of side effects increases at doses higher than 200 mg per day.

In 2023, the European Food Safety Authority set an upper limit of vitamin B6 of 12 mg per day for adults, and 2.2 to 10.7 mg per day for infants and children.

Source: https://inspectsupplement.com/vitamin-b6 (Edited Note: My Website)

I've been taking "Opti-Men" from Optimum Nutrition for like 10 years now and it seems to have 50mg in a (full) serving that I take.

Since B6 is water soluble doesn't it mean most of it might just leave our body if not needed? (No storage in fat)

This is the mechanism of action:

Vitamin B6 is an antioxidant and coenzyme involved in amino acid, carbohydrate and lipid metabolism. Humans cannot directly produce active vitamin B6 (pyrixodal phosphate). However, salvage pathways allow the enzymatic conversion of vitamin B6 vitamers, including pyridoxine, pyridoxal and pyridoxamine by the enzyme pyridoxal kinase, into active vitamin B6.

In the body, active vitamin B6 is involved in metabolic reactions including GABA synthesis, monoamine neurotransmitter metabolism, the metabolism of polyunsaturated fatty acids and phospholipids, amino acid metabolism and the conversion of tryptophan to niacin.

Vitamin B6 reduces homocysteine levels by acting as a coenzyme for both cystathionine-beta-synthase (CBS) and cystathionine-gamma-lyase (CSE) in the transsulfuration pathway following a postprandial methionine-load (after a meal). In the fasting state, homocysteine is primarily metabolised via the remethylation pathway which does not require vitamin B6.

In the transsulfuration pathway, homocysteine is converted to cystathionine by CBS, then to cysteine by CSE. During moderate vitamin B6 deficiency, CSE exhibits much greater loss of activity compared to CBS. However cysteine production is preserved due to an accumulation of cellular and plasma cystathionine in a larger substrate pool which compensates for reduced CSE activity. As CBS is a vitamin B6-dependent enzyme, CBS deficiency (typically genetic causes) can result in elevated fasting and post-methionine load homocysteine due to impaired synthesis of cystathionine from homocysteine. Elevated homocysteine levels increase oxidative stress, may inhibit nitric oxide synthesis, increase vascular endothelial cell damage and accelerate low-density lipoprotein (LDL) deposition in arteries.

Vitamin B6 may significantly decrease the rate of formation of kidney stones in patients with type I primary hyperoxaluria, a condition caused by a deficiency of the liver-specific enzyme alanine-glyoxylate:aminotransferase by reducing levels of urinary oxalate. The protective effect of vitamin B6 supplementation for kidney stones appears to only occur in women (-34% risk) and not men.