High Folate inhibits B12 absorption

[fx9898]

Interesing read on how high levels of Folate could cause issues with b12 absorption.

sciencedirect.com/science/a...

Under conditions of B12 insufficiency, excess folic acid intake will cause the following:

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Diversion of holoTC from serum to hemopoietic cells to support reticulocyte proliferation

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Loss of holoTC in urine due to interference of its reuptake by the megalin-receptor complex in the renal tubules

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Reduced availability of holoTC to the liver, brain, and other tissues due to its diversion to the hemopoietic system and loss in the urine; this, in turn, leads to accentuated elevations in blood concentrations of tHcy and MMA, and exacerbation of neurological sequelae due to vitamin B-12 deficiency in the brain and peripheral nervous system

[Myoldcat]

Very interesting, such a complex interaction. I'm injecting eod, taking 5mg of folic acid each time and recently felt I was backsliding so I cut back on folic acid and have felt better - blood test was 28 before reducing. ... equally, I felt bad when I ran out of folic acid last year at a level of 18, so for me it feels like there's an optimal window. Planning to go to daily 400mcg methylfolate and keep 🤞🤞🤞.Oh, for monthly blood tests...

[Bellabab]

My Consultant prescribed 5mg.folic acid daily and it worked fine. I have since reduced it to 5mg.EOD and I am still fine. I note that the paper speaks of folic acid doses way above the usual levels of supplementation. I cannot eat enough dark green vegetables to meet my folate needs as I would prefer.

[Technoid]

I think your excerpt of the paper above might be a bit misleading out of context. I've posted and discussed this paper a couple times. Bear in mind the effects you describe above are prefixed with a statement that they are the Hypothesized effects of excess folic acid.

I do generally agree that it is worth exercising caution with extremely high doses of folic acid (especially over 1mg). There are other studies and a meta-analysis which suggest to me that it could be making some further tests of high dose folic acid and possibly reviewing the tolerable upper limit.

There is no reason to take 5mg of folic acid in perpetuity if not correcting a deficiency. If injecting B12 at high frequencies consumed such massive amounts of folate, anyone not taking 5mg folic acid would become deficient. Of course they do not, because it is a misunderstanding that frequent high dose B12 would have such an effect on folate.

If one is eating a folate-poor diet AND you have one of the relevant MTHFR variants, a supplement of up to 800mcg may make sense (see the work of Martin Kohlmeier), although 200-400mcg would be enough for most people that have no metabolic issues - only a folate-poor diet. There are other folate forms such as methylfolate or folinic which do not have the same concerns as folic acid. There is also the option of skipping the supplementation and getting up to 1mg by eating a healthy diet. Personal choice.

[Bellabab]

There is no evidence that folate or folic acid causes cancer - just speculation by American fundamentalist Christians. No research into it at all.

[MindfulSquirrel]

I think high dose folate can cause problems for some people (it did with me, and I do suspect it was UMFA). However, I wouldn’t personally trust Ben Lynch as much as I could throw him. There is peer reviewed stuff out there which is more reliable.