What it does in the body
- Oxygen transport (hemoglobin and myoglobin)
- Electron transport chain (energy production)
- DNA synthesis and cell division
- Immune function (lymphocyte proliferation)
- Neurotransmitter synthesis (dopamine, serotonin)
How much you need (Daily Value)
| Group | Recommended | Source |
|---|---|---|
| Adult male | 8 mg | NIH/IOM |
| Adult female | 18 mg (premenopausal), 8 mg (postmenopausal) | NIH/IOM |
| Pregnancy | 27 mg | WHO/IOM |
| Children | 7 mg (1-3y), 10 mg (4-8y), 8-15 mg (9-18y) | NIH/IOM |
| Older adults | 8 mg | NIH/IOM |
Richest food sources
| Food | Amount | Where |
|---|---|---|
| Liver (beef) | 6.5 mg per 100g (heme) | global |
| Oysters | 7.2 mg per 100g (heme) | coastal regions |
| Spinach (cooked) | 3.6 mg per 100g (non-heme) | global |
| Lentils (cooked) | 3.3 mg per 100g (non-heme) | South Asia/Middle East |
| Red meat (beef) | 2.7 mg per 100g (heme) | global |
| Tofu (firm) | 5.4 mg per 100g (non-heme) | East Asia |
| Fortified cereals | 18 mg per serving | Americas/Europe |
| Pumpkin seeds | 8.8 mg per 100g (non-heme) | Americas |
In our food database, per 100 g
Highest among our free foods — open the Food Explorer to compare.
If you don't get enough
Mild: Fatigue, decreased exercise tolerance, poor concentration, pallor
Moderate: Iron deficiency anemia (microcytic, hypochromic), pica, restless legs syndrome, koilonychia (spoon nails), glossitis
Severe: Severe anemia, high-output cardiac failure, impaired cognitive development in children, increased maternal mortality
Time to onset: Iron stores deplete in 3-6 months. Frank anemia develops in 6-12 months of inadequate intake or chronic blood loss.
Too much
Upper limit: 45 mg/day (elemental iron)
Acute iron poisoning (especially in children): GI hemorrhage, metabolic acidosis, liver failure, death. Chronic overload (hemochromatosis): liver cirrhosis, cardiomyopathy, diabetes, bronze skin
How well you absorb it
Heme iron: 15-35%. Non-heme iron: 2-20%. Overall dietary absorption: 14-18% from mixed diet, 5-12% from vegetarian diet
Helped by: Vitamin C (converts Fe3+ to Fe2+), Heme iron (meat factor), Acidic pH, Fermentation (reduces phytate)
Hindered by: Phytate (whole grains, legumes), Polyphenols/tannins (tea, coffee), Calcium (when taken simultaneously), Oxalate, Soy protein
Cooking & storage
Cooking in cast iron cookware significantly increases iron content of food (2-5x increase in acidic foods like tomato sauce). Vitamin C-rich foods added during cooking enhance non-heme iron absorption. Fermentation of grains and legumes reduces phytate, improving iron bioavailability.
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.
