> Vitamin B12 deficiency can cause PGH through unknown mechanism. About 55% of patients with pernicious anemia had graying before 50 years as compared to 30% in the control group.[32]

/soapbox

Get your B12 tested (before taking supplements!).

B12 deficiency is known to present in many ways, and also to be often overlooked in clinical settings[1]. It’s known that not everyone presents with the anaemia from it[2], which is often why it’s skipped as a diagnostic option. Additionally, long-term/severe deficiency can present with symptoms almost identical to multiple sclerosis[3]. Deficiency of other B vitamins, such as B2, can cause a functional B12 deficiency as well[4]. It’s also known that supplementation will falsely elevate levels even in the presence of a deficiency.

/unsoapbox

[1] https://www.mcpiqojournal.org/article/S2542-4548(19)30033-5/...

[2] https://www.bmj.com/content/383/bmj-2022-071725

[3] https://researchonline.nd.edu.au/cgi/viewcontent.cgi?article...

[4] https://www.iomcworld.org/articles/paradoxical-vitamin-b12-d...

The paradoxical B12 deficiency might have a relation with the inactive form being supplemented. If one supplements cyanocobalamin, and one expects the body to convert it to methylcobalamin, and if this conversion doesn't happen for whatever reason, and if the measured form includes the inactive form, then "paradoxical B12 deficiency" can be observed.

There is a more insidious form of it whereby the active form doesn't enter the brain. Symptoms are: difficulty speaking, tremors and ataxia. This can be tested by CSF (cerebrospinal fluid) testing. This assumes that the active form is supplemented and it is present in blood. It can be remedied by a course of corticosteroid pills, followed by megadosing B12 orally daily. Refer to PMID 38924428.

I take a triple active form of it which is methyl+hydroxy+adenosyl, covering all bases, but a total of just 500 mcg per day, above which it harms my sleep.

I take supplemental B12 and a B-complex because I get hair thinning, brittle nails, and peripheral edema and neuropathy without them. (Also taking levothyroxine and slo iron.) I feel way better with it than without it, and it ain't placebo because I have a terrible habit "memory", forget it often, and remember forgetting after my feet remind me. There's a noticeable point 30 to 90 minutes later at which they spontaneously feel better, but I completely forget about taking or not taking them. (I really need a pill planner like an old person.) I wasn't aware of the apparent connection until after numerous episodes and connecting the two.

Also, over half the world's population has H. Pylori, which interferes with B12 absorption.

Interesting. I had it 5 years ago and then it went away. It started again a few weeks ago and I halved my vitamin B supplementing a while before that.

The reason I take B12 as a supplement is unrelated to this - I have MTHFR mutation and as such I need to take methyl folate (methylated B9). Apparently this form of B9 absorbs better if it’s combined with the methylated form of B12 (methylcobalamin)

I guess if it will keep my hair color longer that’s a nice side effect!

It’s also known that supplementation will falsely elevate levels even in the presence of a deficiency.

It sounds to me that what you’re saying is that a daily multivitamin would not help in this case.