Vitamin B12

维生素 B12

Place · Level 3

只有细菌会造 · 需要胃里出门票 · 让神经有外套，让 DNA 能复印

Connected to · 11

synergy · 3

Vitamin B6
B12 + folate run remethylation; B6 routes Hcy to transsulfuration. Any one short and Hcy rises.
TMG / Betaine
TMG fuels the BHMT backup; when MTR is limited by B12 / folate / MTHFR, betaine carries Hcy back to methionine.
Magnesium
Magnesium participates in several B12-dependent methylation steps.

cofactor · 3

Folate
B12 + folate run the methylation cycle together. Folate alone masks B12 deficiency anemia.
Nervous
Adenosylcobalamin-dependent MUT failure mis-incorporates odd-chain fatty acids into myelin → subacute combined degeneration. Reversible <6 mo, permanent >12 mo. MMA is the most sensitive biomarker.
Zinc
Gastric acid production needs zinc; deficiency indirectly impairs B12 release from food.

antagonism · 1

Spirulina
Spirulina contains pseudocobalamin — chemically near-identical to real B12 but unusable by humans AND competes for absorption receptors. 'Vegan B12 from spirulina' is one of the most dangerous marketing claims on the atlas — serum B12 looks normal while nerve damage continues.

depletes · 3

Drug–Nutrient
Long-term metformin impairs the calcium-dependent ileal step of B12 absorption; DPPOS shows risk rising ~1.13× per year, so periodic B12 checks are routine monitoring.
Type 2 Diabetes
Metformin is first line, cheap, with decades of safety data, and one of its costs is that long-term use drags vitamin B12 down — the mechanism being interference with calcium-dependent uptake in the terminal ileum. Not a reason to stop it; a reason to monitor.
GERD
A real cost of long-term acid suppression: B12 in food is protein-bound and needs stomach acid and pepsin to release it. Suppress the acid and that step stalls, which is why long-term PPI users need their B12 watched.

regulates · 1

Chronic Fatigue
B12 deficiency is a standard stop on a fatigue work-up, and the high-risk groups are easy to name: older adults, vegans, long-term metformin or PPI users. Found and corrected, it belongs to the reversible layer, not to chronic fatigue.

Food

Stop 1/6

食物

B12 (cobalamin) is the largest and most complex of all the vitamins — at its core is a cobalt (Co) ion wrapped by a corrin ring, structurally homologous to heme (which holds Fe) and chlorophyll (which holds Mg).

One key fact: only prokaryotes (bacteria and archaea) have the enzymes to synthesize B12. Plants, fungi, and animals cannot make it — animals accumulate B12 by eating microbe-laden forage or via gut microbial symbionts, and then concentrate it in liver, muscle, eggs, and milk. So dietary B12 comes almost entirely from animal sources:

Clams: ~99 µg / 100 gBeef liver: ~70 µg / 100 g (off the charts)Salmon, tuna: ~4-7 µg / 100 gEggs: ~0.6 µg per eggMilk: ~1.3 µg per cup
The RDA is only 2.4 µg/day — a small number. But plant sources are almost all unreliable:

Dried purple laver (nori) is the exception: it carries real, bioactive B12, and the Watanabe 2014 review concludes it is the most suitable naturally occurring plant source available to vegetarians — though content varies widely by species and processing, so relying on it for a steady intake is not realisticSpirulina and chlorella are where the pseudo-B12 analogs live: structurally similar, biologically inert, and able to occupy the absorption routeUnfermented legumes and nuts: noneFortified foods (fortified breakfast cereal, plant milks) contain real B12 — for vegans, this is the only reliable plant-based dietary source of B12
So strict or near-vegan eaters typically need fortified foods plus a supplement.

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Educational content, not medical advice — consult a clinician.

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