What it does in the body
- Central metal ion in vitamin B12 (cobalamin)
- DNA synthesis (via methionine synthase/B12)
- Red blood cell formation
- Myelin synthesis and nervous system maintenance
- Methylation reactions (methionine cycle)
How much you need (Daily Value)
| Group | Recommended | Source |
|---|---|---|
| Adult male | No RDA for cobalt; 2.4 mcg of B12 provides adequate cobalt | NIH |
| Adult female | No RDA for cobalt; 2.4 mcg of B12 provides adequate cobalt | NIH |
| Pregnancy | 2.6 mcg B12 equivalent | WHO/IOM |
| Children | 0.9-1.8 mcg B12 equivalent by age | NIH |
| Older adults | 2.4 mcg B12 (may need supplemental form due to atrophic gastritis) | NIH |
Richest food sources
| Food | Amount | Where |
|---|---|---|
| Beef liver | 70.7 mcg B12 per 100g | global |
| Clams | 98.9 mcg B12 per 100g | coastal regions |
| Sardines | 8.9 mcg B12 per 100g | Mediterranean |
| Beef | 5.9 mcg B12 per 100g | global |
| Salmon | 3.2 mcg B12 per 100g | global |
| Fortified nutritional yeast | 23.0 mcg B12 per 100g (fortified) | global (supplement) |
| Milk | 0.5 mcg B12 per 100ml | global |
| Eggs | 1.1 mcg B12 per 100g | global |
If you don't get enough
Mild: Fatigue, mild cognitive changes (reflects B12 deficiency)
Moderate: Megaloblastic anemia, glossitis, peripheral neuropathy
Severe: Subacute combined degeneration of spinal cord, severe anemia, irreversible neurological damage
Time to onset: B12 stores last 3-5 years; deficiency symptoms develop slowly over 1-3 years after stores depleted.
Too much
Upper limit: No established UL for dietary cobalt. Inorganic cobalt supplementation is not recommended.
Cobalt toxicity (cobaltism): cardiomyopathy (beer drinker's cardiomyopathy historically), polycythemia (cobalt stimulates erythropoietin), thyroid dysfunction, neurological impairment. Primarily from industrial exposure or prosthetic wear debris.
How well you absorb it
Cobalt as B12: absorbed via intrinsic factor in ileum (50-70% at physiological doses). Inorganic cobalt: absorbed but not biologically useful and potentially toxic.
Helped by: Intrinsic factor (for B12-bound cobalt), Adequate gastric acid (for B12 release from food)
Hindered by: Pernicious anemia (lack of intrinsic factor), Atrophic gastritis, Metformin, Proton pump inhibitors
Cooking & storage
B12 (cobalt-containing vitamin) is relatively heat-stable but can be degraded by prolonged cooking, especially at high pH. Losses of 10-30% with typical cooking. Fermented foods may contain B12 analogs that are not bioactive.
Nutrisize Health totals every nutrient from what you actually eat, against targets set for your age and sex, and flags what's short — across 4,995 foods, on your device.
