Understanding What Form of Iron is Better Absorbed by the Body?

October 30, 2025 •

3 min read

According to the World Health Organization, iron deficiency is the most common nutritional deficiency worldwide. Understanding what form of iron is better absorbed by the body is crucial for maintaining optimal health, especially for those at risk of deficiency, including women, children, and vegetarians.

Quick Summary

The body absorbs iron in two main forms: heme and non-heme. Heme iron, from animal sources, is significantly more bioavailable and less affected by other dietary factors. Non-heme iron, found in plant foods, is less efficiently absorbed but can be optimized with smart food pairings, like vitamin C.

Key Points

Heme vs. Non-Heme: Heme iron, from animal sources like meat and fish, is better absorbed than non-heme iron, found in plant-based foods.
Enhance Non-Heme Absorption: Pairing non-heme iron with vitamin C-rich foods significantly improves its uptake by the body.
Inhibit Iron Absorption: Compounds like phytates in grains, tannins in tea and coffee, and calcium can inhibit the absorption of non-heme iron.
Meat Factor Benefit: Eating heme iron alongside non-heme iron enhances the absorption of the non-heme iron.
Supplement Forms: Chelated iron supplements like ferrous bisglycinate may be better absorbed and cause fewer side effects than traditional iron salts like ferrous sulfate.

Iron is a critical mineral involved in numerous bodily functions, most notably forming hemoglobin to transport oxygen throughout the body. Dietary iron exists in two distinct forms: heme and non-heme, which the body absorbs differently. Heme iron, found in animal products, is more readily absorbed. Non-heme iron is found in both plant and animal foods and is less bioavailable, but its absorption can be enhanced.

The Two Types of Dietary Iron

Heme Iron: The High-Efficiency Option

Heme iron is part of hemoglobin and myoglobin in animal tissues and is highly bioavailable, with an absorption rate of 15% to 35%. Its absorption is less affected by other dietary components compared to non-heme iron.

Sources of heme iron:

Meat: Red meat and organ meats.
Poultry: Chicken and turkey.
Seafood: Clams, oysters, mussels, tuna, and salmon.

Non-Heme Iron: The Plant-Based Form

Non-heme iron is present in plant foods and fortified products. It is the main dietary iron source for most people, but its absorption is lower, ranging from 2% to 20%. Its uptake is significantly influenced by other foods consumed simultaneously.

Sources of non-heme iron:

Legumes: Lentils, beans, and chickpeas.
Vegetables: Dark leafy greens and potatoes with skin.
Nuts and Seeds: Pumpkin seeds, sesame seeds, and cashews.
Fortified Foods: Cereals, bread, and pasta.

Factors Influencing Iron Absorption

Enhancing Non-Heme Iron Absorption

Vitamin C: Consuming vitamin C with non-heme iron foods greatly increases absorption. Examples include combining lemon juice with spinach or orange juice with fortified cereal.
Meat, Fish, and Poultry: Animal protein, the “meat factor,” boosts non-heme iron absorption when eaten together.
Cast Iron Cookware: Cooking in cast iron can increase food's non-heme iron content.

Inhibiting Iron Absorption

Phytates: Found in grains and legumes, phytates reduce non-heme iron absorption. Soaking or sprouting can help.
Tannins and Polyphenols: In tea, coffee, and red wine, these compounds inhibit non-heme iron absorption. Drink them between meals.
Calcium: Calcium can hinder the absorption of both iron types. Avoid consuming high-calcium foods or supplements with iron-rich meals.

Comparing Heme and Non-Heme Iron


Feature	Heme Iron	Non-Heme Iron
Primary Sources	Meat, poultry, seafood, organ meats	Plant-based foods (legumes, grains, vegetables), fortified foods
Absorption Rate	Higher (15-35%) and more consistent	Lower (2-20%) and more variable
Affected by Diet?	Minimal interference from other dietary factors	Strongly influenced by enhancers (vitamin C, meat factor) and inhibitors (phytates, tannins)
Absorption Pathway	Absorbed intact through a separate pathway	Requires reduction (from ferric to ferrous state) before absorption
Risk of Overload	Absorption not tightly regulated, can lead to overload with consistently high intake in susceptible individuals	Tightly regulated by the body, making overload from dietary sources less likely

What About Iron Supplements?

For diagnosed deficiency, supplements may be recommended. Most supplements contain non-heme iron, such as ferrous sulfate. Chelated forms like iron bisglycinate may be better absorbed with fewer side effects. To maximize absorption, supplements are often taken on an empty stomach with vitamin C, away from high-calcium foods.

Ferrous Sulfate: Common, but can cause digestive issues.
Ferrous Bisglycinate: Chelated form, potentially better absorbed and gentler.
Supplementation Strategy: Take as directed, often with vitamin C and away from certain foods.

Conclusion

Heme iron from animal sources offers superior absorption, but a balanced diet combining heme and non-heme sources with absorption-enhancing strategies is effective for most individuals. Vegetarians and vegans can meet their needs by focusing on vitamin C pairings and proper preparation of plant foods. Supplements, particularly chelated forms, can help those with deficiencies under medical guidance. A personalized dietary approach considering both iron types is key for healthy iron levels. Consult a healthcare professional or dietitian for tailored advice.

For more detailed scientific information on iron metabolism and dietary factors, the American Journal of Clinical Nutrition is a valuable resource for research and reviews.

Frequently Asked Questions

Animal products such as red meat, poultry, and fish contain both heme and non-heme iron. Heme iron is the more easily absorbed form derived from the hemoglobin and myoglobin in these foods.

Vegetarians can increase non-heme iron absorption by pairing iron-rich plant foods like lentils and spinach with a source of vitamin C, such as citrus fruits, bell peppers, or tomatoes.

Yes, tea and coffee contain polyphenols and tannins that can inhibit non-heme iron absorption. It is best to consume these beverages between meals rather than with iron-rich foods.

It is not recommended to take iron supplements with calcium, as calcium can interfere with the absorption of both heme and non-heme iron. Space out your intake by at least one to two hours.

No, the absorption of non-heme iron varies widely and is dependent on your body's iron stores and the presence of enhancers or inhibitors in the meal. Foods containing phytic acid or oxalic acid can significantly reduce absorption.

Yes, some supplements are better tolerated and absorbed. Organic iron bisglycinate is a chelated form often cited for good absorption and fewer side effects compared to traditional iron salts like ferrous sulfate.

The 'meat factor' is a term referring to the beneficial effect that consuming meat has on enhancing non-heme iron absorption when both are eaten in the same meal.