Vitamin B12 (Cobalamin)
vitamin
ApprovedGeneral information about nutrients. No diagnosis, no medical advice. If you take medication, are pregnant or have a medical condition, talk to your doctor before taking supplements.
Overview
Vitamin B12 contributes to normal red blood cell formation. Vitamin B12 contributes to normal functioning of the nervous system. Deficiency common in older adults and vegans.
Interactions
B12 and folate are co-dependent in the methionine synthase reaction. B12 demethylates methylfolate to regenerate THF, the active folate form. Deficiency of either blocks the methylation cycle.
Research status
Vitamin B12 contributes to normal homocysteine metabolism.
Top 5 food sources
Expert opinions
Dr. Strunz
Strunz rejects the standard lab cut-off of 200 to 300 pg/ml as far too low. He targets serum B12 of 800 to 1,200 pg/ml and backs it up with holo-transcobalamin (the metabolically active fraction, should be >50 pmol/L) and methylmalonic acid (should be <270 nmol/L) to catch functional deficiency missed by total B12 alone. He supplements 500 to 1,000 mcg of methylcobalamin (or adenosylcobalamin), never cyanocobalamin, because the active forms need no conversion step. B12 deficiency is common after age 60, with metformin or PPIs, in vegans, and after bariatric surgery.
Recommended dose: 500–1000 mcg
Source: Dr. Strunz
Expert profiles summarise publicly available statements. The named people do not cooperate with Stackwell and have not authorised these summaries. Not medical advice.
No known toxicity. Supplementation broadly recommended for at-risk groups.