Vitamin B12 (cobalamin) is essential for red blood cell formation, neurological function, and nucleic acid metabolism. Natural sources are almost exclusively animal-based. For mechanisms, guidelines, and safety, see the professional fact sheet on vitamin B12.
Top 15 — vitamin B12-rich foods
Indicative guidelines (µg/100 g or per common serving); variations depending on species, part, farming method, processing, and cooking. For precise values, consult the Ciqual table (ANSES) and FoodData Central (USDA).
- Clams/cockles: very rich, often > 50 µg/100 g
- Liver (beef/veal/lamb): ~40–100 µg/100 g
- Whelks/oysters/mussels: ~10–40 µg/100 g
- Sardines (fresh/canned): ~8–14 µg/100 g
- Mackerel/herring: ~8–20 µg/100 g
- Tuna (canned/fresh): ~2–10 µg/100 g
- Salmon/trout: ~2–7 µg/100 g
- Beef (steak, braised): ~1–4 µg/100 g
- Aged cheese: ~0.5–3 µg/100 g
- Yogurt/milk (per 150–250 ml): ~0.4–1.5 µg
- Eggs (2 medium): ~0.8–1.5 µg
- Poultry offal: ~10–25 µg/100 g
- Crab/spider crab/shrimp: ~1–10 µg/100 g
- Fortified products (breakfast cereals, plant-based beverages, nutritional yeast): variable (check label)
- Butcher meats (pork/lamb): ~1–3 µg/100 g
Examples: 1 small can of sardines (90–100 g) can cover > 100% of a common guideline; 1 serving of liver (100–120 g) far exceeds the goal; 2 eggs provide a useful contribution daily.
Optimizing absorption
- Intrinsic factor and gastric acidity: B12 absorption requires an intrinsic factor and sufficient gastric acidity. PPIs/H2 blockers and gastric atrophy can reduce absorption. See the absorption section of the NIH ODS fact sheet.
- Medications: metformin and PPIs decrease absorption; nitrous oxide can inactivate B12. In case of chronic treatment, discuss monitoring.
- Cooking: moderate losses depending on duration/temperature; favor gentle cooking.
- Fortified foods (cereals, plant-based beverages, fortified nutritional yeast): useful for vegetarians/vegans.
- Supplement forms: cyanocobalamin, methylcobalamin, hydroxocobalamin (choice based on tolerance/regimen).
Daily guidelines (recommended intakes)
References differ by organization. Usual international guidelines: ≈ 2.4 µg/day for adults, ≈ 2.6 µg/day pregnancy, ≈ 2.8 µg/day breastfeeding — see the professional synthesis. European references set an adequate intake ≈ 4 µg/day for adults (slight variations by age/state).
| Population | Daily guideline |
|---|---|
| Adults | ≈ 2.4–4 µg/day (depending on reference) |
| Pregnancy | ≈ 2.6–4.5 µg/day |
| Breastfeeding | ≈ 2.8–5 µg/day |
| Vegetarians/vegans | favor fortified foods and/or supplementation |
Risks, interactions and precautions
- Deficiency: megaloblastic anemia, neurological disorders (paresthesias, gait disturbances), glossitis. See our vitamin B12 deficiency symptoms.
- At-risk groups: vegans, elderly, malabsorption (intestinal diseases, bariatric surgery), treatments (metformin, PPIs).
- Upper limit (UL): not established (low toxicity) according to the NIH ODS B12 fact sheet.
- Interactions: caution with metformin, PPIs/H2 blockers, nitrous oxide; evaluate the need for supplementation and biological monitoring (e.g., holo-TC, methylmalonic acid, homocysteine).
Natural B12 comes mainly from animal foods; in a vegan diet, using fortified foods and/or a supplement is essential to meet needs.
Sources and further reading
- Mechanisms, guidelines, safety: professional fact sheet on vitamin B12.
- Composition tables: Ciqual table (ANSES) and FoodData Central (USDA).
- European references: adequate intakes close to 4 µg/day (see reference reports).
