Non-heme iron: foods, absorption and blood tests

Plant foods can contribute to your iron supply. They provide non-heme iron, which is also found in eggs and fortified products. The body absorbs about 2–20 % of it, considerably less than from heme iron. How much is actually absorbed depends in part on the meal: vitamin C promotes absorption, while phytates from grains and legumes, polyphenols from tea and coffee, and calcium can inhibit it.

Lentils, fortified breakfast cereals, tofu, pumpkin seeds and dark leafy greens supply plant-based iron. Whether your iron stores are adequately filled, though, cannot be read from your menu alone. The blood test ferritin helps with the assessment; on its own, it does not answer every diagnostic question.

What non-heme iron is and why it matters

Iron occurs in food in two chemical forms. Heme iron is found in meat, poultry and fish, where it is part of the proteins hemoglobin and myoglobin. During absorption, the iron enters the gut cells together with the surrounding heme structure as an intact complex; chemically, this structure is called a metalloporphyrin complex.

Non-heme iron is not bound into such a heme complex. It occurs in legumes, dark leafy greens, whole grains, nuts, seeds, eggs, dairy products and iron-fortified foods.

The two forms differ mainly in their bioavailability, meaning how much iron the body absorbs and can use. The body absorbs about 15–35 % of heme iron, and this share is relatively stable. For non-heme iron it is 2–20 %, depending among other things on what else is in the digestive tract. Especially on a diet with little or no meat, it is therefore worth looking at which foods end up on the plate together. Monsen, 1988

Plant sources of non-heme iron

Legumes: lentils, chickpeas and beans

Legumes are among the most important plant sources of iron. One cup of cooked lentils, about 200 g, provides 6–7 mg of iron. The quantities given for chickpeas are 4–5 mg, and for kidney beans and black beans 3–5 mg. Eaten regularly, legumes can therefore make a substantial contribution to iron intake.

For comparison, reference values of 8 mg a day for adult men and 18 mg for premenopausal women are cited. These values do not apply everywhere and should not be read here as German reference values.

Legumes also contain phytates, however, which reduce iron absorption. Soaking dried legumes for several hours before cooking and then pouring off the soaking water lowers their phytate content. This improves the bioavailability of the iron.

Tofu and tempeh

Half a cup of firm tofu provides roughly 3 mg of iron. Tempeh, a fermented soy product, contains a comparable amount. Fermentation lowers the phytate content. This could mean the body absorbs the iron better than from unfermented soy. Tofu and tempeh also supply protein and combine easily with vitamin C-rich ingredients in a meal.

Fortified breakfast cereals and bread

Fortified breakfast cereals can provide 4–18 mg of iron per serving, which makes them especially iron-rich. The amount depends on the product. Fortification often uses elemental iron, which the body absorbs to varying degrees depending on its form. Vitamin C from orange juice or fresh fruit improves absorption from such cereals.

The added iron compound also makes a difference: ferrous sulfate and ferrous fumarate are absorbed better than elemental iron powder. Which form was used is not always clear from the label, however.

Pumpkin and sesame seeds

For shelled pumpkin seeds, a figure of roughly 4–5 mg of iron per 30 g serving has been given. If this value were accurate, they would be a particularly iron-rich plant-based snack. The figure is uncertain, however.

Sesame seeds and tahini, a paste made from sesame seeds, also supply notable amounts of iron. Their phytates do reduce absorption, but seeds can round out the diet thanks to their high nutrient density. Foods that promote iron absorption go well with them.

Dark leafy greens

Spinach, Swiss chard and cooked kale are considered sources of iron. Raw spinach provides roughly 2.7 mg of iron per 100 g. The content alone, however, does not tell you how much of it the body absorbs.

Oxalates are cited as a possible explanation for limited absorption. These compounds can form poorly soluble complexes with iron. This is the basis for the assumption that spinach supplies less available iron than its content would suggest, and that cooking reduces the inhibition somewhat. How much this relationship actually matters for iron absorption from spinach remains open. Monsen, 1988

The recommendation to choose Swiss chard or bok choy instead for an iron-rich diet also rests on an assumed lower oxalate content. No established advantage can be derived from this at present, particularly not for Swiss chard over spinach.

Dried fruit

Dried apricots and raisins provide about 2–3 mg of iron per 100 g, along with naturally occurring sugars and fiber. As a snack, they can add to iron intake over the day. The figure refers to 100 g, though; because dried fruit is so energy-dense, people usually eat smaller amounts.

What can improve non-heme iron absorption

Get vitamin C in the same meal

Vitamin C with a meal is one of the best-supported dietary ways to improve non-heme iron absorption. Ascorbic acid, to use its chemical name, works in two ways: it converts ferric iron (Fe3+) into more easily absorbed ferrous iron (Fe2+). It also binds iron in what is called a chelate complex, which keeps it soluble in the alkaline environment of the gut. Teucher et al., 2004

As little as about 25–50 mg of vitamin C can markedly increase non-heme iron absorption. In everyday life, you can add vitamin C with lemon juice on a lentil dish, bell pepper in a leafy salad, or a small glass of orange juice with iron-fortified breakfast cereal.

Don’t drink tea and coffee with iron-rich meals

Polyphenols in black tea, green tea, coffee and red wine bind non-heme iron in complexes that the body absorbs less well. This can substantially reduce the amount of iron absorbed. Hurrell et al., 1999

A gap of 1–2 hours before or after an iron-containing meal is suggested. This is meant to reduce the inhibiting effect; whether this gap is equally sufficient for all the drinks mentioned is an open question. Paying attention to timing may make sense especially for people who drink tea or coffee often and rely mostly on plant sources of iron.

Calcium and iron in the same meal

Calcium can inhibit the absorption of both heme and non-heme iron when the two are taken at the same time. Spreading calcium-rich foods such as dairy products or calcium-fortified plant drinks, as well as calcium supplements, across other meals is meant to reduce this effect. It does not automatically follow, however, that taking them together worsens iron status in the long term. Lönnerdal, 2010

Use soaking, sprouting and fermenting

Soaking, sprouting and fermenting lower the phytate content of legumes and grains. With dried beans, it helps to soak them overnight and pour off the water before cooking. During sprouting, grains and legumes activate enzymes that break down phytates. Fermentation too, as in tempeh, miso and sourdough bread, lowers the phytate content and can markedly improve the bioavailability of iron. Monsen, 1988

Cook in cast-iron cookware

When acidic foods are cooked, small amounts of iron pass from cast-iron pots into the food. This applies, for example, to tomato sauces or dishes with citrus. That way, cooking can raise iron intake slightly without any extra step. When iron needs are high, however, this small contribution is not enough to serve as the main measure. Brittin and Nossaman, 1986

Which blood tests help assess iron status?

A dietary analysis shows how much iron the foods you eat contain. How much of it the body absorbs and stores cannot be reliably read from it. Blood tests help assess iron status.

• Ferritin gives clues about iron stores and can signal early that they are running down.
• Serum iron describes the iron currently circulating in the blood. The value fluctuates more than ferritin.
• TIBC, total iron-binding capacity, rises when iron stores are depleted.
• Transferrin saturation indicates what share of the binding sites on the transport protein transferrin are occupied by iron. It falls when iron supply is inadequate.
• Hemoglobin and MCV help assess anemia. MCV describes the average volume of red blood cells. In iron deficiency, these values may only fall once stores are already significantly depleted.

Ferritin is particularly important here: hemoglobin and the blood count can still look normal even though iron stores have already dropped considerably. A low ferritin value can point to this. When an inadequate iron supply is suspected, ferritin is therefore part of a targeted assessment. A normal blood count alone does not rule out iron deficiency; nor is ferritin on its own enough for a diagnosis in every situation.

Iron needs, testing and supplements

The body absorbs about 15–35 % of heme iron and 2–20 % of non-heme iron. For non-heme iron, the share depends on the meal, existing iron stores and gut health. When iron stores are low, the body increases absorption of both forms, but the relative difference remains. To account for the lower bioavailability, an iron intake of roughly 1.8 times the recommendation for people on a mixed diet is cited for vegetarians and vegans. This factor is a context-dependent reference assumption, not a blanket individual recommendation for Germany. van Wonderen et al., 2023

Iron needs can also be met with plant foods alone. Deliberate food choices and combinations that promote absorption help. Ferritin checks can show how well supplied you are, because a dietary analysis does not reliably predict individual iron status. Whether regular checks make sense, and how often, depends on your personal situation.

If you are tired and suspect low iron, a ferritin test can tell you more than your memory of what you ate recently. Even plenty of plant iron sources on the menu do not guarantee adequate absorption, for instance if inhibiting substances regularly turn up in the same meal. A normal hemoglobin value does not rule out depleted iron stores. Ferritin helps with the workup, but on its own it does not answer the question of what is causing the fatigue.

Whether an iron supplement makes sense can be assessed together with a medical professional based on measured iron status, including ferritin. Guesses about your diet are not enough for this. When iron stores are adequate, extra iron carries risks, including gastrointestinal complaints and, at high doses, possible oxidative effects. Supplementation should therefore be guided by demonstrated need. Auerbach et al., 2025

This article is for information only and does not replace medical advice. Changes to health measures should be discussed with a qualified medical professional. The links to individual blood tests lead to additional information.

Frequently asked questions

What is the difference between heme iron and non-heme iron?

Heme iron occurs in meat, poultry and fish, where it is bound into the proteins hemoglobin and myoglobin. The body absorbs it as an intact complex; the absorbed share is 15–35 %. Non-heme iron is not bound into a heme complex and is found in plant foods, eggs, dairy products and fortified products. The body absorbs about 2–20 % of it.

How much non-heme iron is absorbed depends heavily on what else is in the digestive tract. Vitamin C promotes absorption, while phytates and polyphenols inhibit it. For heme iron, the absorbed share is relatively stable.

Which plant foods are especially rich in non-heme iron?

Cooked lentils provide 6–7 mg per cup. For chickpeas and kidney beans, the amounts given here are 3–5 mg per cup. Fortified breakfast cereals contain 4–18 mg per serving, and half a cup of firm tofu about 3 mg. For pumpkin seeds, a figure of roughly 4–5 mg per 30 g serving is cited; this value is uncertain.

Dark leafy greens such as Swiss chard and bok choy also contribute to iron intake. For spinach, the binding of iron by oxalates is considered a possible explanation for why the body absorbs less of it despite its notable iron content. How strongly oxalates actually affect absorption is not settled here.

How does vitamin C improve non-heme iron absorption?

Vitamin C, also called ascorbic acid, converts ferric iron (Fe3+) into more easily absorbed ferrous iron (Fe2+). It also binds iron in a chelate complex. This keeps the iron soluble in the alkaline environment of the gut so that it can be absorbed there.

As little as about 25–50 mg can markedly increase absorption from a plant-based meal. A small glass of orange juice or a few pieces of bell pepper are rough food examples of this amount.

Do tea and coffee reduce iron absorption from plant foods?

Yes. Polyphenols in black tea, green tea, coffee and red wine form poorly soluble complexes with non-heme iron in the gut. As a result, the body absorbs considerably less iron. Anyone who drinks these beverages with or right after an iron-rich meal may therefore absorb less iron despite a high plant iron intake. That alone, however, does not mean their iron supply is inadequate.

A gap of 1–2 hours before or after iron-containing meals is meant to reduce the inhibiting effect of tea or coffee. Whether this time frame applies equally to all the drinks mentioned is an open question.

Why is spinach considered a source of iron if its iron is not well absorbed?

Raw spinach contains roughly 2.7 mg of iron per 100 g, which is a notable amount. Iron content, however, is not the same as the amount absorbed. Its high oxalate content is cited as an explanation for limited absorption: oxalates can bind iron in poorly soluble complexes that pass through the gut unabsorbed.

This explanation underlies the assumption that the body absorbs considerably less iron from raw spinach than its content would suggest. The claims that cooking weakens this effect somewhat, and that Swiss chard or bok choy are more available iron sources because of lower oxalate content, follow the same line of reasoning. How strong the oxalate effect really is, and whether the alternatives mentioned offer an advantage, remains unresolved. In particular, no established advantage of Swiss chard over spinach can be derived from this.

Which preparation methods improve the bioavailability of non-heme iron?

Soaking dried legumes overnight and pouring off the soaking water before cooking lowers their phytate content and so improves the bioavailability of the iron. When grains and legumes sprout, phytase enzymes become active and break down phytates. Fermentation, as in tempeh, miso and sourdough bread, also lowers the phytate content considerably.

When acidic foods are cooked in cast-iron cookware, small but measurable amounts of iron pass into the food. Vitamin C in the same meal can further promote absorption.

Why is ferritin a particularly important blood test for assessing iron status?

Ferritin gives clues about the iron stores in body tissues and can signal early that they are running down. The value can fall before serum iron, hemoglobin or red blood cell measurements change.

So hemoglobin and the blood count can still look normal even though iron stores are already significantly depleted and a low ferritin value points to this. A normal blood count alone can miss this phase before anemia. That is why ferritin is part of a targeted assessment when diet-related iron deficiency is possible. As a single value, however, it does not allow a reliable diagnosis in every situation.

Do vegetarians and vegans have a higher risk of iron deficiency?

A higher risk of depleted iron stores is mainly attributed to the lower absorption of non-heme iron, which is what iron supply on a plant-based diet relies on: the body absorbs about 2–20 % of it, compared with 15–35 % for heme iron. In addition, phytates and polyphenols may more often be present in the same iron-rich meal and inhibit absorption. These relationships alone, however, do not determine an individual’s personal risk.

To offset the lower bioavailability, an iron intake of roughly 1.8 times the recommendation for people on a mixed diet is cited. This factor is a context-dependent reference assumption, not a blanket individual target. Ferritin measurements can say more about a person’s own iron supply than a dietary analysis alone. Whether regular checks are needed depends on the individual situation.

Sources

• Monsen ER (1988). Iron nutrition and absorption: dietary factors which impact iron bioavailability. Journal of the American Dietetic Association, 88(7), 786-90. https://pubmed.ncbi.nlm.nih.gov/3290310/
• Teucher B, Olivares M, Cori H (2004). Enhancers of iron absorption: ascorbic acid and other organic acids. International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition, 74(6), 403-19. https://doi.org/10.1024/0300-9831.74.6.403 PubMed
• Hurrell RF, Reddy M, Cook JD (1999). Inhibition of non-haem iron absorption in man by polyphenolic-containing beverages. The British journal of nutrition, 81(4), 289-95. https://pubmed.ncbi.nlm.nih.gov/10999016/
• Lönnerdal B (2010). Calcium and iron absorption–mechanisms and public health relevance. International journal for vitamin and nutrition research. Internationale Zeitschrift fur Vitamin- und Ernahrungsforschung. Journal international de vitaminologie et de nutrition, 80(4-5), 293-9. https://doi.org/10.1024/0300-9831/a000036 PubMed
• Brittin HC, Nossaman CE (1986). Iron content of food cooked in iron utensils. Journal of the American Dietetic Association, 86(7), 897-901. https://pubmed.ncbi.nlm.nih.gov/3722654/
• van Wonderen D, Melse-Boonstra A, Gerdessen JC (2023). Iron Bioavailability Should be Considered when Modeling Omnivorous, Vegetarian, and Vegan Diets. The Journal of nutrition, 153(7), 2125-2132. https://doi.org/10.1016/j.tjnut.2023.05.011 PubMed
• Auerbach M, DeLoughery TG, Tirnauer JS (2025). Iron Deficiency in Adults: A Review. JAMA, 333(20), 1813-1823. https://doi.org/10.1001/jama.2025.0452 PubMed