Legumes are among the most useful plant sources of iron, but different beans and pulses do not provide identical amounts. Dry and cooked numbers also differ sharply because cooking adds water. For a plate-level comparison, cooked values per 100 g are the clearest starting point.
Approximate iron ranking per 100 g cooked
| Cooked legume | Iron | Approx. protein |
|---|---|---|
| Mature soybeans | ~5.1 mg | ~18.2 g |
| White beans | ~3.7 mg | ~9.7 g |
| Lentils | ~3.3 mg | ~9.0 g |
| Kidney beans | ~2.9 mg | ~8.7 g |
| Chickpeas | ~2.9 mg | ~8.9 g |
| Black beans | ~2.1 mg | ~8.9 g |
These are USDA-style cooked references and vary somewhat by cultivar and preparation. Mature soybeans stand out, providing roughly 2 mg more iron per 100 g than lentils and more than twice the amount in the black-bean reference.
The ranking shows concentration, not whether a lower-ranked bean is unimportant. A one-milligram difference per 100 g can be offset by portion size, frequency, or what else is eaten with the meal. Black beans, for example, can still make a meaningful contribution if they appear regularly in larger servings.
Serving size changes the picture
A 200 g serving of cooked lentils at 3.3 mg iron per 100 g provides about 6.6 mg iron. Two hundred grams of chickpeas at 2.9 mg per 100 g provide about 5.8 mg. Both are meaningful sources even though lentils rank somewhat higher.
That is why ranking per 100 g and planning a meal are different questions. A 150–250 g serving can turn a moderate per-100-g food into a substantial contributor to daily intake. It also makes the rest of the plate relevant: a bean bowl with vegetables and whole grains is nutritionally different from a small garnish of beans.
Plant iron is nonheme iron
Iron in legumes is nonheme iron. Its absorption varies more than heme iron from meat and seafood and is influenced by phytate, polyphenols and enhancers such as vitamin C.
NIH estimates overall iron bioavailability at about 14–18% in mixed diets and roughly 5–12% in vegetarian diets. Those percentages describe whole diets, not a fixed absorption rate for one bean.
Do not convert the table directly into a fixed amount “absorbed.” The body regulates iron absorption partly according to iron status, and the rest of the meal changes how much nonheme iron becomes available. Someone with low iron stores may absorb differently from someone whose stores are adequate, so food-composition data and individual iron status answer different questions.
Pair legumes with vitamin C
Vitamin C improves nonheme-iron absorption. Bell peppers, tomatoes, broccoli, citrus, kiwi or strawberries alongside beans or lentils can matter more for absorbed iron than a few tenths of a milligram separating two legume varieties.
This is easy to apply without special recipes: tomato and peppers in a bean dish, citrus in a salad, or a vitamin-C-rich fruit with the meal can accompany the iron source. The combination matters most as a meal habit rather than as a perfect formula that has to be measured every time.
Do not mix dry and cooked values
Dry legumes contain far less water, so iron, protein and calories are more concentrated per 100 g. A dry value of 7–8 mg iron per 100 g cannot be compared directly with 3 mg per 100 g cooked as though the portions were equivalent.
When comparing food tables or labels, always check whether the entry is dry, cooked, or drained. A lower cooked value often reflects dilution by absorbed water, not a proportional disappearance of iron. The same issue affects protein and calorie rankings, which is why preparation state should be consistent across the entire comparison.
What about canned beans?
Canned beans remain cooked legumes and still provide iron, protein and fiber. Sodium is the main practical difference when salt is added to the packing liquid. Draining and rinsing can cut sodium by about 40% on average in tested canned beans.
For iron, the label and drained serving are more useful than assuming canned beans are nutritionally inferior. Convenience may also make it easier to eat legumes more often. If a can turns beans into a regular weeknight food instead of an occasional one, that frequency can matter more than a small difference between database entries.
Bottom line
Mature soybeans, white beans and lentils are among the iron-richest common cooked legumes in these references. The serving size, vitamin C in the meal and whether the number is dry or cooked are all part of interpreting that ranking. Choose among them for taste, convenience, protein, fiber and the rest of the meal rather than treating a few tenths of a milligram as a decisive gap.
Sources
- USDA FoodData Central — Cooked composition references for soybeans, white beans, lentils, kidney beans, chickpeas and black beans.
- NIH Office of Dietary Supplements — Iron — Heme versus nonheme iron, dietary bioavailability and factors that affect absorption.