All rankings of iron-rich foods lie a little. They arrange foods by milligrams per 100 grams, which places spirulina, cocoa and sesame seeds at the top, and makes you believe that a spoonful of algae is worth a serving of blood sausage. Yet what matters is not the iron you eat, it's the iron your intestine lets through, and the difference ranges from 2% to 35% depending on the food and what accompanies it.
This article re-ranks foods by absorption, explains the two types of iron, details the best animal and plant sources, the food combinations that double intake, the pitfalls that cancel it out, provides two sample days at 16 mg, and honestly says when diet alone is no longer enough. For the rest (symptoms, ferritin, blood work), the complete guide to iron deficiency.
The most concentrated natural vitamin C in the plant kingdom, in powder form to dilute in water or sprinkle over meals. One spoonful with lentils, tofu or your morning iron capsule, and the absorption of non-heme iron can double or triple.
There are two types of iron. Heme iron from animal products (blood sausage, liver, shellfish, red meat, sardines) is absorbed at 15 to 35% no matter what. Non-heme iron from plants, eggs and supplements is absorbed at 2 to 20% depending on the meal: vitamin C multiplies it by 2 to 3, tea and coffee divide it by 2 to 5, calcium and phytates slow it down. Ranked by iron actually absorbed, the podium becomes black pudding, clams and mussels, liver, then beef and sardines; on the plant side, lentils, tofu, beans and pumpkin seeds provided they are combined with vitamin C, away from tea. Spinach and spirulina are overrated. ANSES requirements: 11 mg per day, 16 mg for women with heavy periods or pregnant women. When losses exceed what diet provides, a well-absorbed supplement takes over.
1. Two irons, two absorptions
The heme iron represents 10 to 15% of iron ingested in a Western diet, but up to 40% of iron absorbed, because heme is captured as-is by intestinal cells, without binding to the tannins or phytates in the meal. Non- heme iron, on the other hand, must be released from food by gastric acidity, reduced to ferrous form, then captured by a transporter that it shares with other minerals; at each step, it can be trapped. This is why its absorption ranges from 2% (meal rich in tea and whole grains) to 20% (meal with vitamin C and meat) (Hurrell and Egli, Am J Clin Nutr, 2010).
Practical consequence: a ranking by crude iron content tells us almost nothing about actual intake. You must multiply the content by absorption, and by the portion you actually eat.
2. Ranking by actually absorbed iron
| Food (portion) | Total iron | Type | Estimated absorption | Iron absorbed |
|---|---|---|---|---|
| Blood sausage (100 g) | 22 mg | Heme | 20 to 25% | 4.5 to 5.5 mg |
| Clams, cockles (100 g shelled) | 10 to 15 mg | Predominantly heme | 15 to 25% | 2 to 3.5 mg |
| Calf or poultry liver (100 g) | 8 to 10 mg | Heme | 20 to 25% | 2 mg |
| Mussels (100 g shelled) | 6 to 8 mg | Predominantly heme | 15 to 25% | 1.2 to 1.8 mg |
| Beef (150 g) | 3 to 4 mg | Hemic at 60% | 20% | 0.7 to 0.9 mg |
| Cooked lentils (200 g) + vitamin C | 4 to 6 mg | Non-hemic | 8 to 12% | 0.4 to 0.7 mg |
| Sardines (100 g) | 2.5 to 3 mg | Hemic at 50% | 15 to 20% | 0.4 to 0.6 mg |
| Firm tofu (150 g) + vitamin C | 4 to 5 mg | Non-hemic | 6 to 10% | 0.3 to 0.5 mg |
| Pumpkin seeds (30 g) | 2.5 to 3 mg | Non-hemic | 5 to 8% | 0.15 to 0.25 mg |
| Cooked lentils (200 g) with tea | 4 to 6 mg | Non-hemic | 2 to 3% | 0.1 to 0.2 mg |
| Spirulina (3 g, one teaspoon) | 0.8 mg | Non-hemic | 5 to 10% | 0.05 to 0.1 mg |
| Cooked spinach (200 g) | 4 to 5 mg | Non-heme, oxalates | 1 to 3% | 0.05 to 0.15 mg |
Content data from the Ciqual table (ANSES) and scientific literature; absorption estimates based on single-meal studies in subjects with normal iron stores (Hurrell and Egli 2010). In iron-deficient individuals, absorption of all foods increases, particularly for non-heme iron. Orders of magnitude, not laboratory values.
3. The best animal sources
- Black pudding : 22 mg/100 g, the champion in all categories. A 100 g serving alone covers one-third to half of your daily absorbed iron needs. Fatty and salty, it should be eaten once a week, not every day.
- Shellfish : clams, cockles, mussels, oysters. Iron, zinc and B12 in abundance, low in calories. Canned clams also count.
- Organ meats : veal liver, poultry liver, beef liver, kidneys. 8 to 10 mg/100 g. Liver is also very rich in vitamin A: once a week, and should be avoided during pregnancy.
- Red meat : beef, lamb, duck, 2 to 4 mg/100 g, of which 60% is heme iron. The "meat factor" also improves absorption of plant iron from the same meal.
- Fatty fish : sardines, mackerel, tuna. 1 to 3 mg/100 g, with omega-3s as a bonus. White fish contains little.
- What is not a source : eggs (1.5 mg, non-heme, and a protein in the yolk inhibits absorption), dairy products (virtually zero, and calcium inhibits it), white poultry (less than 1 mg).
4. The best plant sources, and the overrated ones
Legumes: lentils, chickpeas, red and white beans
3 mg per 100 g cooked, in generous portions. Their iron is inhibited by phytates; soaking for 12 hours, sprouting and fermentation degrade them and can multiply absorption by 2 (Sandberg, Br J Nutr, 2002). Always with a vitamin C-rich food.
Tofu, tempeh, edamame
Firm tofu provides 3 to 5 mg/100 g. Tempeh, being fermented, has fewer phytates than tofu. Soy protein slightly inhibits absorption: vitamin C compensates.
Seeds and nuts: pumpkin, sesame, hemp, cashews, almonds
High content (8 to 15 mg/100 g) but small portions (30 g) and abundant phytates. Tahini and toasted seeds sprinkled on food are an easy daily supplement, not a main source.
Cocoa, whole grains, dried fruits
Unsweetened cocoa powder displays 10 to 15 mg/100 g but its polyphenols inhibit absorption; 70% dark chocolate provides 1 to 2 mg per square-serving. Quinoa, oats, sourdough whole grain bread (fermentation degrades phytates), dried apricots and dried figs complement.
Spinach
2 to 3 mg/100 g cooked, of which 1 to 3% is absorbed due to oxalates, which trap iron. The reputation comes from a 19th-century decimal error perpetuated by Popeye. Spinach remains excellent for other reasons (folates, magnesium, vitamin K), not for iron.
Spirulina
28 mg/100 g, real and impressive content. But we consume 3 to 5 g per day, which equals 0.8 to 1.4 mg of non-heme iron, absorbed at only a few percent. Our organic spirulina has real advantages (proteins, phycocyanin, beta-carotene); correcting low ferritin is not one of them. With a source of vitamin C, its iron contribution improves without becoming decisive.
5. Combinations that double iron intake
| Lever | Effect on non-heme iron | How |
|---|---|---|
| Vitamin C | x 2 to 3 starting at 50 to 100 mg at the same meal; neutralizes some phytates and polyphenols | A kiwi (80 mg), half a red bell pepper (80 mg), an orange (60 mg), parsley, broccoli, strawberries, or a spoonful of acerola powder in a glass of water at mealtime |
| Meat factor | Increases absorption of plant-based iron from the same meal | 50 g of meat, fish or seafood in a lentil or bean dish |
| Soaking, sprouting, fermenting | Break down phytates; absorption up to doubled (Sandberg 2002) | Legumes soaked 12 hours and rinsed; sprouted seeds; sourdough bread rather than yeast bread; tempeh, miso |
| Organic acids | Citric, malic, lactic acids: keep iron soluble | Lemon juice on vegetables, sauerkraut, lacto-fermented vegetables, tomatoes |
| Cast iron | Measurable iron transfer, especially with acidic foods simmered | Tomato sauce, ratatouille, chili in a cast iron pot or skillet |
| Vitamin A and beta-carotene | Probable favorable effect, less documented | Carrots, sweet potato, butternut squash at the same meal |
6. Pitfalls that cancel out iron intake
- Tea and coffee at meals : -60 to -90% for tea, -40 to -80% for coffee on non-heme iron from the meal. Green tea is no exception to the rule. Solution: consume them one to two hours after.
- Dairy products and calcium : -30 to -50% from 150 to 300 mg of calcium, for both types of iron. Cheese at the end of an iron-rich meal or yogurt at breakfast with lentils are not good ideas; dairy products belong at another meal.
- Bran, non-fermented whole grains, non-fermented soy : phytates. Sourdough bread, soaking and sprouting solve a good part of the problem.
- Red wine, cocoa, iced tea, herbal teas rich in tannins : polyphenols; moderate but real with meals.
- Eggs : phosvitin in the yolk slows iron absorption from the meal; one egg doesn't negate anything, but it's not the "iron source" we think it is.
- Breakfast cereals "fortified with iron" : often elemental iron (metal iron powder) poorly absorbed, served with milk and sometimes tea. The iron on the label doesn't reach the bloodstream.
- "Rich in iron" on the packaging : the claim is allowed from 30% of the NRV per 100 g, without accounting for absorption or actual portion size. A powder at 28 mg/100 g of which you consume 3 g is "rich in iron" and provides almost nothing.
7. Two sample days at 16 mg
The message from these two days: even very well constructed, the vegetarian plate absorbs about twice as little iron as the omnivore's despite higher content. This is why the references for vegetarians are multiplied by 1.8, and why a menstruating vegetarian woman is well-advised to check her ferritin annually.
8. When the plate is no longer enough
Even when deficient, the intestines absorb barely 3 to 5 mg of dietary iron per day. To raise ferritin from 10 to 50 µg/L, approximately 500 mg of reserves must be rebuilt: at 3 mg per day, that's six months without any loss, which doesn't exist in menstruating women. This is why leading medical journals recommend supplemental intake as soon as deficiency is established, with food then serving to prevent relapse (Pasricha, Lancet, 2021; Camaschella, Blood, 2019).
The rules of a balanced plate then apply to the capsule: iron in the morning on an empty stomach, with vitamin C, away from tea, coffee, dairy products and other minerals, a single dose, every other day for high doses (Stoffel 2017), a form that is absorbed and well-tolerated over several months. It all comes down to when to take iron, and ferritin thresholds in low ferritin: what to do.
14 mg of iron chelated to glycine, 80 mg of vitamin C already in the capsule, 200 µg of vitamin B9. Absorbed 2 to 4 times better than ferrous salts, with no metallic taste or constipation. One capsule in the morning, and your diet does the rest. Made in France.
Discover Bisglycinate Iron →Not recommended in case of hemochromatosis, during pregnancy and breastfeeding without medical advice. To be taken only in case of confirmed deficiency.
Choose the situation that applies to you: the answer appears just below.
A heme source two to three times per week (shellfish, blood sausage, beef, sardines), legumes soaked with vitamin C on other days, tea and coffee away from meals, dairy products consumed away from iron-rich meals. Check ferritin every two or three years, yearly if you are a menstruating woman.
Ask for ferritin and CRP (and B12). Then, each main meal should combine a legume or tofu, a source of vitamin C, and no tea or dairy. Soaking and sourdough systematically, acerola at the table. If ferritin is below 30 despite this, a well-absorbed supplement is justified, while rebuilding levels.
You probably eat enough iron; you're preventing it from being absorbed. Tea and coffee one to two hours away from meals, cheese and yogurt away from iron-rich meals, vitamin C at lunch and dinner. If ferritin remains low after three months of these adjustments, investigate a source of loss (periods, digestive) with your doctor.
At 3 mg absorbed per day at best, against losses that often exceed this figure, diet alone will not rebuild 500 mg of reserves. A well-absorbed supplement (bisglycinate with vitamin C) taken correctly, especially with medical guidance during pregnancy, for 3 to 6 months, then diet to maintain. And the cause to be treated: see heavy periods and iron deficiency.
This test provides guidance, it does not replace professional medical advice.
Frequently asked questions about iron-rich foods
Which food contains the most iron?
In raw content, spirulina (28 mg/100 g) and blood sausage (22 mg/100 g) dominate, followed by clams, liver and sesame seeds. But the useful ranking is that of absorbed iron: blood sausage and shellfish, whose iron is heme-based and absorbed at 15 to 35%, provide much more real iron than a spoonful of spirulina, whose plant iron is absorbed at 2 to 10%.
What is the difference between heme and non-heme iron?
Heme iron comes from hemoglobin and myoglobin in animal products (meat, organ meats, fish, shellfish); it is absorbed at 15 to 35% and relatively resistant to inhibitors. Non-heme iron is that from plants, eggs, dairy products and all supplements; it is absorbed at 2 to 20% depending on what accompanies it, and very sensitive to tea, coffee, calcium and phytates.
Are spinach really rich in iron?
No. Cooked spinach contains 2 to 3 mg of iron per 100 g, non-heme iron that is very poorly absorbed due to oxalates. The legend comes from a decimal point error reproduced in the 19th century. Lentils, tofu, and pumpkin seeds are much better plant-based sources.
Is spirulina a good source of iron?
Its iron content is remarkable (28 mg/100 g), but a teaspoon of 3 g provides only 0.8 mg, absorbed at just a few percent. It complements a diet, it does not correct low ferritin. When taken with a source of vitamin C, its actual bioavailability improves.
How to better absorb iron from plants?
Add vitamin C to the same meal (citrus fruits, kiwi, bell pepper, parsley, acerola), which can double or triple absorption; soak, sprout, or ferment legumes and grains to break down phytates; combine with a little meat or fish (meat factor); and keep tea, coffee, and dairy products away from the meal.
Do tea and coffee really prevent iron absorption?
Yes, significantly: the tannins in tea can reduce non-heme iron absorption by 60 to 90% at the same meal, the polyphenols in coffee by 40 to 80%. The effect disappears if the beverage is consumed one to two hours after the meal.
How much iron is needed per day?
According to ANSES, 11 mg per day for men and women with low menstrual losses, 16 mg for women with heavy periods, 16 mg also for pregnant women. These are ingested intakes, not absorbed amounts: they assume absorption of approximately 10 to 15%.
Can a vegetarian meet their iron needs?
Yes, with care: since plant iron is less bioavailable, needs are estimated to be 1.8 times higher. Soaked legumes, tofu, seeds, sprouted whole grains, always with vitamin C and without tea at meals. Annual ferritin monitoring is reasonable, especially for menstruating women.
Does cooking in a cast iron skillet provide iron?
Yes, measurably: acidic foods (tomato sauce) simmered in cast iron can gain several milligrams of iron. It is a supplement, not a strategy, but it is real.
When is diet no longer enough?
When losses exceed what the intestine can absorb: heavy periods, pregnancy, endurance sports, strict plant-based diet, repeated blood donations, or ferritin already below 30 µg/L. Diet maintains adequate reserves; it rarely builds up depleted reserves. A well-absorbed and tolerated supplement then takes over, on the advice of a healthcare professional.
- Heme iron
- Iron from hemoglobin and myoglobin, present in animal flesh, absorbed at 15 to 35%.
- Non-heme iron
- Mineral iron from plants, eggs, and supplements, absorbed at 2 to 20% depending on the meal.
- Phytates
- Compounds found in whole grains, legumes, and seeds that trap iron; broken down by soaking, sprouting, and fermentation.
- Meat factor
- Effect of animal proteins that increases the absorption of plant iron from the same meal.
- Ciqual
- ANSES nutritional composition table of foods, French reference for nutrient content.
- Hurrell R, Egli I. Iron bioavailability and dietary reference values. Am J Clin Nutr. 2010;91(5):1461S-1467S. doi:10.3945/ajcn.2010.28674F
- Sandberg AS. Bioavailability of minerals in legumes. Br J Nutr. 2002;88 Suppl 3:S281-S285. doi:10.1079/BJN/2002718
- Pasricha SR, Tye-Din J, Muckenthaler MU, Swinkels DW. Iron deficiency. Lancet. 2021;397(10270):233-248. doi:10.1016/S0140-6736(20)32594-0
- Camaschella C. Iron deficiency. Blood. 2019;133(1):30-39. doi:10.1182/blood-2018-05-815944
- Stoffel NU, Cercamondi CI, Brittenham G, et al. Iron absorption from oral iron supplements given on consecutive versus alternate days and as single morning doses versus twice-daily split dosing in iron-depleted women. Lancet Haematol. 2017;4(11):e524-e533. doi:10.1016/S2352-3026(17)30182-5
- ANSES. Ciqual nutritional composition table of foods. ciqual.anses.fr
- ANSES. Nutritional reference values for vitamins and minerals (2021). anses.fr
