Just wondering if Vitamin B12 is necessary for the body to utitlize folate. My husband is on Methotrexate for rheumatoid arthritis, a medicine which is known to destroy folate. The doctors therefore prescribe high dose folic acid. He also, however, has a geographic tongue which is supposedly due to B12 defiency. If he is deficient in B12, and yet if B12 is necessary for folate absorption, the extra folic acid is presumably doing no good. Whether the two vitamins are essential co-factors is interesting to know because I've just read that folic acid deficiency gives people a 69% higher risk of heart disease. And he's just had a massive heart attack.

I can't seem to find the answer on standard search engines, would be grateful to know whether B12 is needed to utilize folate. Many thanks.

  • $\begingroup$ From Wikipedia: "In the form of a series of tetrahydrofolate (THF) compounds, folate derivatives are substrates in a number of single-carbon-transfer reactions, [...] It is a substrate for an important reaction that involves vitamin B12 and it is necessary for the synthesis of DNA, ...". $\endgroup$ – try-catch-finally Dec 27 '17 at 20:22
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    $\begingroup$ B12 deficiency is not the cause of benign migratory glossitis. It is the cause of pernicious anemia, though. $\endgroup$ – anongoodnurse Dec 28 '17 at 16:08

B12 is not necessary to utilize folate but it is necessary to replace B12 before repleting folate as otherwise you can induce subacute combined degeneration of the cord. There are multiple mechanisms of folate absorption from the small bowel and large bowel which don't require B12.

Geographic tongue is not caused by B12 deficiency, and the actual cause is not known. It does cause raw beef tongue.

You don't normally need to prescribe mega doses of folic acid with methotrexate. Common doses are 5 mg per week, and 0.8 mg daily, though some physicians don't bother using folic acid at all. Although folic acid was commonly prescribed because it was believed that methotrexate works by virtue of its ability to antagonize folic acid, it is now known that this is not true. It works as an adenosine antagonist, and so you can take the folic acid on the same day as the methotrexate if you wish.


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