Who's Actually at Risk for B12 Deficiency
B12 deficiency gets framed as a vegan-diet problem — but a surprisingly large share of meat-eaters are deficient for a completely different reason.
B12 absorption depends on intrinsic factor, a stomach protein, and adequate stomach acid to release B12 from food protein in the first place — not just dietary intake. Common medications (proton pump inhibitors, metformin) and normal age-related declines in stomach acid production can block absorption even when B12 intake from meat, eggs, or dairy is completely adequate.
Key Findings
- B12 deficiency is often driven by absorption failure, not intake
- Long-term PPI and metformin use are each linked to reduced B12 status
- Deficiency risk rises with age regardless of diet type
- A meat-inclusive diet doesn't rule out deficiency
The absorption mechanism most people miss
B12 absorption depends on intrinsic factor and adequate stomach acid to release B12 from food protein — not just how much B12 is in your diet. Studies estimate B12 deficiency affects a meaningful share of older adults independent of diet type, driven primarily by absorption failure rather than intake — a distinct mechanism from the vegan/vegetarian dietary-intake deficiency more commonly discussed.1
The medications that quietly interfere
Long-term metformin and PPI (proton pump inhibitor) use are each independently associated with reduced B12 status in multiple studies, and deficiency risk in older adults rises regardless of whether meat is part of the diet.2
Why the "vegan problem" framing is incomplete
The vegan/vegetarian intake-based deficiency is real and well-documented, but it's a different mechanism from absorption failure — and absorption failure doesn't care what's on your plate.
The practical takeaway
- A diet that includes meat, eggs, or dairy doesn't rule out B12 deficiency if absorption is impaired
- Anyone on long-term PPI or metformin therapy has a real reason to get levels checked, regardless of diet
- Age over roughly 60 is an independent risk factor due to naturally declining stomach acid production
Sources
- "Vitamin B12 deficiency in older adults: absorption mechanisms." PMC. pmc.ncbi.nlm.nih.gov
- "Metformin and proton pump inhibitor use associated with B12 deficiency." Clinical literature review.
