Where is Heme Found?: Dietary, Biological, and Supplemental Sources

December 11, 2025 •

4 min read

Heme is an iron-containing compound that is a crucial component of hemoglobin, the protein in red blood cells responsible for transporting oxygen throughout the body. This essential molecule is not only produced naturally within the body but is also a key nutrient obtained from certain dietary sources. Understanding where heme is found can provide valuable insight into iron absorption and overall health.

Quick Summary

Heme is an iron-containing compound found in animal-based foods like red meat and poultry, and is naturally present in the hemoglobin of red blood cells and myoglobin of muscle tissue. This article details the primary dietary and biological locations of heme, clarifies the difference between heme and non-heme iron, and discusses supplemental forms.

Key Points

Dietary Source: Heme iron is exclusively found in animal products, including red meat, poultry, fish, and organ meats.
High Bioavailability: The body absorbs heme iron much more efficiently (15-35%) than non-heme iron, which is found in plants.
Biological Locations: Heme is predominantly found in hemoglobin within red blood cells and myoglobin in muscle tissue, where it binds oxygen.
Cellular Importance: All cells contain hemoproteins like cytochromes, which use heme to facilitate the electron transport chain during cellular respiration.
Internal Production: The body synthesizes its own heme primarily in the bone marrow and liver.
Supplemental Forms: Heme iron polypeptide is a supplemental form offering better absorption and fewer gastrointestinal side effects than non-heme iron supplements.

Heme in the Human Body

Within the human body, heme is an integral part of several crucial proteins known as hemoproteins. Its primary biological function is centered around its ability to bind oxygen, a role most prominently displayed in the circulatory and muscular systems. The body produces its own heme primarily in the bone marrow and liver.

Hemoglobin and Red Blood Cells

Over 85% of the body's heme is found within hemoglobin, the protein that gives red blood cells their characteristic color. Each hemoglobin molecule contains four heme groups, allowing it to efficiently transport oxygen from the lungs to the body's tissues. This process is fundamental to cellular metabolism and energy production.

Myoglobin and Muscle Tissue

Heme is also a component of myoglobin, a protein found in the heart and skeletal muscles. Unlike hemoglobin, which transports oxygen, myoglobin is responsible for storing oxygen within muscle cells, ready for release during periods of physical activity. This ensures a steady supply of oxygen to active muscles, delaying fatigue.

Cellular Respiration and Enzymes

Beyond oxygen transport and storage, heme is a necessary prosthetic group for enzymes involved in the electron transport chain, a vital part of cellular respiration that generates energy in the form of ATP. Proteins such as cytochromes, which are found in the mitochondria of virtually every cell, rely on heme to shuttle electrons. Other heme-dependent enzymes include catalase and nitric oxide synthase, which play roles in antioxidant defense and signaling.

Dietary Sources of Heme

In terms of nutrition, heme is one of two primary forms of dietary iron. It is exclusively found in animal products, specifically in the flesh and muscle tissue, making it a key part of carnivorous and omnivorous diets.

Foods High in Heme Iron

Red Meat: Beef, lamb, and venison are excellent sources, with the deepest red meats typically containing the highest concentrations.
Organ Meats: The liver and kidney of animals are particularly rich in heme iron due to their metabolic functions.
Poultry: Chicken and turkey are good sources of heme iron, with darker meat containing more than lighter meat.
Seafood: Shellfish such as oysters, clams, and mussels are among the highest dietary sources of heme iron. Various types of fish like salmon and tuna also provide a significant amount.

Comparison: Heme vs. Non-Heme Iron

Non-heme iron is found in plant-based foods, dairy, and fortified products. The body absorbs heme iron much more efficiently (15-35%) than non-heme iron (2-20%). This difference is crucial for individuals with low iron levels or those following vegetarian or vegan diets, who must consume more iron to achieve the same absorption levels.


Feature	Heme Iron	Non-Heme Iron
Source	Animal-based foods (meat, poultry, fish)	Plant-based foods, fortified foods, dairy, eggs
Absorption Rate	Higher (15-35%)	Lower (2-20%)
Absorption Pathway	Absorbed intact via specialized transport pathway	Requires enzymatic reduction; influenced by other dietary factors
Affected by Inhibitors?	Minimal interference from phytates, tannins, calcium	Significantly inhibited by phytates, polyphenols, calcium
Enhancers	Non-heme iron absorption is enhanced by its presence	Enhanced by vitamin C, inhibited by coffee and tea

Supplemental Heme Iron

For those needing to boost their iron intake, supplements are available in various forms, including heme iron. Heme iron polypeptide is a supplemental form that leverages the higher bioavailability of heme iron. Studies have shown that heme iron supplements can offer a number of advantages over traditional non-heme iron supplements, which often cause gastrointestinal side effects like constipation. By utilizing the distinct absorption pathway, heme iron supplements can be gentler on the stomach and effectively increase iron levels. These supplements are often recommended for individuals who don't tolerate conventional iron salts well or for certain high-risk populations. However, it is essential to consult a healthcare provider before starting any new supplement regimen.

Conclusion

In conclusion, heme is a vital molecule found in two distinct realms: the biological systems of the body and the dietary world of animal products. Internally, it is concentrated within red blood cells as part of hemoglobin and in muscle tissue as myoglobin, and is crucial for cellular energy production. Externally, heme is obtained from animal sources, such as red meat, poultry, and fish, and is also available in specialized supplements. The higher bioavailability of dietary heme iron makes it a potent source of this essential nutrient. Understanding the varied locations and functions of heme underscores its significance for maintaining healthy iron levels and overall physiological function, from oxygen delivery to energy metabolism. For more in-depth information on dietary iron, consult authoritative sources like the National Institutes of Health.(https://www.ncbi.nlm.nih.gov/books/NBK540969/)

Frequently Asked Questions

The primary function of heme is to bind oxygen. It is a critical component of hemoglobin, which transports oxygen in red blood cells, and myoglobin, which stores oxygen in muscle tissue.

Heme iron is found exclusively in animal-based foods. This includes red meat (beef, lamb), poultry (chicken, turkey), organ meats (liver), and seafood (clams, oysters, fish).

No, plants do not contain heme. The iron found in plants is called non-heme iron, which is absorbed differently and less efficiently by the body compared to heme iron.

Heme iron has a distinct absorption pathway in the small intestine, allowing it to be absorbed intact. Non-heme iron absorption, in contrast, is more complex and can be inhibited by other dietary components like phytates and tannins.

Heme is primarily produced in the bone marrow for incorporation into red blood cells and in the liver for other metabolic functions. All cells, however, are capable of synthesizing heme to some extent.

Yes, supplemental forms of heme are available, most commonly as heme iron polypeptide. These supplements are often favored for their high bioavailability and fewer gastrointestinal side effects compared to traditional iron salts.

Yes, heme iron can enhance the absorption of non-heme iron when consumed together in a meal, an effect known as the 'meat factor'. This is one reason why consuming meat can boost overall iron levels more effectively.