Vitamin B12: the deficiency that threatens vegetarians (and not only them)
Vitamin B12 is found almost only in animal products. Roles, who's at risk, neurological symptoms and why vegans must supplement. Evidence-based.
Key takeaways
- B12 is found almost only in animal products (meat, fish, eggs, dairy).
- Vegans must supplement, no exception; vegetarians need monitoring too.
- A deficiency can cause neurological damage, sometimes irreversible if prolonged.
- Older people absorb B12 less well, even with a mixed diet.
Vitamin B12 is a special case among micronutrients: our body can't make it, and it's almost absent from the plant kingdom. It's the only deficiency for which supplementation isn't optional for vegans. Little known, it can nonetheless cause serious neurological damage when it sets in. Here's what matters.
What vitamin B12 does
B12 (cobalamin) is essential to three vital functions: red blood cell formation (its deficiency causes a so-called megaloblastic anaemia), nervous system function (the myelin sheath of nerves), and DNA synthesis. It's this dual impact, on blood and nerves, that makes the deficiency both insidious and potentially serious (Stabler, NEJM 2013).
Who is at risk
Three main profiles. Vegans and vegetarians first: since B12 is nearly absent from plants, deficiency risk is high without supplementation (Pawlak et al., 2013). Older people next: with age, intestinal B12 absorption declines, even with a varied diet. Finally, people with digestive disorders (gastritis, Crohn's disease, stomach surgery, long-term antacids), because B12 absorption depends on a factor produced by the stomach.
A deficiency not to let linger
Neurological damage (tingling, balance and memory problems) can become irreversible if the deficiency lasts months or years. Better to prevent and screen early.
Symptoms
- •Fatigue and weakness (linked to anaemia).
- •Tingling, numbness in hands and feet.
- •Memory, concentration and mood problems.
- •Balance and gait problems (advanced forms).
- •Glossitis (smooth, sore tongue), paleness.
Food sources
| Food | Why it helps |
|---|---|
| Liver, offal | By far the richest |
| Meat, poultry | Good regular source |
| Fish, shellfish | Rich (clams, sardines) |
| Eggs | Top-up source |
| Dairy | Useful for vegetarians |
| Fortified foods / supplements | Essential for vegans |
Supplementation: non-negotiable for vegans
For anyone excluding all animal products, B12 supplementation is mandatory: no fully plant-based diet reliably covers the needs (algae and fermented products don't contain usable active B12). Good news: B12 is safe, excess is eliminated, and regular supplementation (daily or weekly depending on dose) is enough. Vegetarians and older people should have their status checked. If in doubt, a blood test (B12, possibly homocysteine) takes stock.
The vegan/vegetarian habit
A daily B12 supplement (cyanocobalamin or methylcobalamin), and an occasional blood test. Simple, safe, and it avoids years of silent deficiency.
Tracking your B12 intake is especially useful when cutting back on animal products: visualising your meals highlights a shortfall before it becomes a neurological problem.
Frequently asked questions
Do algae and fermented soy provide B12?
No, not reliably. They may contain inactive analogues that don't replace real B12. Vegans must rely on a supplement or fortified foods.
Cyanocobalamin or methylcobalamin?
Both work. Cyanocobalamin is the most studied, stable and affordable. Methylcobalamin is an active form often preferred but without a clearly proven advantage for most people.
Can you overdose on B12?
Very unlikely: B12 is water-soluble and excess is excreted in urine. It's one of the safest supplements, hence sometimes high doses without harm.
Is a vegetarian (eating eggs and dairy) covered?
Potentially, if they eat them regularly and in quantity. But deficiency risk stays higher than in omnivores: checking status is wise.
Scientific sources
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