Iron: heme vs non-heme, absorption, and who is at risk
Adults need roughly 11 to 16 mg of iron a day, but the milligrams on a label are not the milligrams you absorb. Iron from meat and fish (heme iron) is absorbed at around 15 to 35 percent; iron from plants, eggs and dairy (non-heme iron) at roughly 2 to 20 percent, depending on what else is on the plate. That absorption gap, not total intake, explains why iron deficiency is the world's most common nutrient shortfall: the WHO estimates anaemia affects about 30 percent of women aged 15 to 49 globally. The fix is rarely heroic. It is knowing which foods carry usable iron and which meal habits quietly block it.
11 mg men, 16 mg premenopausal women (EFSA).
~15 to 35% from meat and fish.
~2 to 20%, swayed by the rest of the meal.
Two kinds of iron, one big difference
Heme iron sits inside the haemoglobin and myoglobin of animal muscle and blood. Your gut has a dedicated uptake route for it, so absorption is high and fairly stable. A portion of lean beef mince (about 2.6 mg iron per 100 g in reference tables, alongside 21.7 g of protein on the Dietly label) delivers more usable iron than a much larger number printed on a plant food.
Non-heme iron is everything else: legumes, grains, vegetables, eggs, fortified foods. Its absorption is opportunistic and heavily influenced by the meal around it. Phytates in whole grains and legumes, oxalates in some greens, polyphenols in tea and coffee, and calcium all reduce uptake; vitamin C and meat in the same meal increase it. This is why spinach, the cartoon iron food, underdelivers: its iron is largely bound to oxalate, and only a small percentage is absorbed. Lentils and calcium-set tofu are the stronger plant plays.
| Food (Dietly label linked) | Typical iron per 100 g | Type | Practical note |
|---|---|---|---|
| Beef mince | ~2.6 mg | Heme + non-heme | High absorption; also boosts uptake of plant iron eaten with it |
| Red lentils, dry | ~7 mg dry (~3.3 mg cooked) | Non-heme | Pair with vitamin C (peppers, citrus) to raise uptake |
| Tofu | ~3 mg | Non-heme | Reliable vegan staple, 10 g protein per 100 g on the label |
| Oats | ~4 mg | Non-heme | Phytates limit uptake; still adds up as a daily staple |
| Spinach | ~2.7 mg | Non-heme | Oxalate-bound, poorly absorbed; eat it for folate and vitamin K |
| Dark chocolate | ~7 mg | Non-heme | Genuinely iron-rich, but 450 kcal per 100 g on the label |
Who actually runs short
- Premenopausal women. Menstrual losses are the reason the reference intake jumps from 11 to 16 mg a day, and heavy periods can outrun a good diet.
- Pregnancy. Blood volume expands and the requirement rises sharply; screening and supplementation are standard care in most countries.
- Vegans and vegetarians. All-plant diets rely on the low-absorption pathway, so recommended intakes are often quoted up to 1.8 times higher. Entirely doable with legumes, tofu, oats and vitamin C pairing, but not automatic.
- Endurance athletes. Foot-strike haemolysis, sweat losses and exercise-driven hepcidin all nibble at iron status, especially in female runners.
- Frequent blood donors and people with gut conditions. Coeliac disease, inflammatory bowel disease and bariatric surgery all impair absorption.
Simple habits that move absorption
Three changes cover most of the practical ground. First, add vitamin C to plant-iron meals: peppers, tomatoes, citrus or berries in the same sitting can multiply non-heme uptake severalfold. Second, move tea and coffee an hour away from iron-rich meals; their polyphenols are potent blockers. Third, if you eat meat, even small amounts alongside beans or grains raise the absorption of the plant iron on the same plate, the so-called meat factor. Track whether your staples actually carry protein and energy in the ranges you expect by checking their labels through Dietly search, and if you are building high-iron meals around a protein target, the protein calculator sets the daily frame.
Do not supplement blind
Iron is unusual among nutrients: the body has no active way to excrete an excess, and both deficiency and overload cause real harm. Unneeded supplements commonly cause constipation and nausea, can mask other problems, and are dangerous for the roughly 1 in 300 northern Europeans with hereditary haemochromatosis. A ferritin blood test costs little and answers the question properly. If it is low, dosing and duration are a conversation with a clinician, not a guess in a supplement aisle.
Bottom line
Aim for 11 to 16 mg a day, but think in absorbed iron, not label iron. Meat and fish deliver reliably; plant iron works when you pair it with vitamin C and keep tea and coffee away from meals. Spinach is overrated, lentils and tofu are underrated, and a ferritin test beats any amount of guessing. For the wider picture of vitamins and minerals, see what are micronutrients.
Sources
Common questions
How much iron do I need per day?
EFSA sets the reference intake at 11 mg a day for adult men and postmenopausal women, and 16 mg a day for premenopausal women, because menstrual losses raise the requirement. Pregnancy raises needs further.
Is spinach a good source of iron?
Not as good as its reputation. Spinach contains a few milligrams of iron per 100 g, but oxalates bind it, so only a small percentage is absorbed. Lentils, tofu and red meat deliver more usable iron per portion.
Should I take an iron supplement?
Only after a blood test. Iron deficiency and iron overload are both harmful, and supplements commonly cause digestive side effects. A ferritin test tells you whether you need more iron; guessing does not.