Why Are There Two Types of Iron?

November 23, 2025 •

3 min read

Heme iron is absorbed up to five times more efficiently by the body than non-heme iron, making it a powerful dietary nutrient. This difference in bioavailability explains why there are two types of iron that impact your nutritional strategy and overall health differently.

Quick Summary

The two primary dietary forms of iron are heme, from animal sources, and non-heme, from plants and fortified foods. Heme iron is more efficiently absorbed by the body due to its molecular structure, while non-heme iron absorption is influenced by other dietary factors.

Key Points

Heme vs. Non-Heme: Dietary iron comes in two forms: heme, found in animal sources, and non-heme, found in plants and fortified foods.
Absorption Efficiency: Heme iron is absorbed much more efficiently by the body (15–35%) than non-heme iron (less than 17%).
Enhancers Matter for Non-Heme: Vitamin C is a critical enhancer for non-heme iron absorption, while inhibitors like phytates and polyphenols can hinder it.
Meat Factor Boosts Absorption: Consuming heme iron (meat) alongside non-heme iron can significantly increase the absorption of the non-heme form.
Dietary Strategies: To maximize iron intake, especially for vegetarians, combine non-heme sources with vitamin C and avoid inhibitors during meals.
Health Impact: Understanding the two types of iron is vital for preventing iron deficiency anemia and maintaining energy, immunity, and overall health.

The Two Forms of Dietary Iron

Iron is an essential mineral vital for transporting oxygen and supporting energy metabolism. Dietary iron comes in two forms: heme and non-heme. These differ in source, structure, and absorption efficiency, a crucial distinction, especially for those on plant-based diets.

Heme Iron: The Animal-Derived Form

Heme iron is found in animal flesh as part of hemoglobin and myoglobin. This structure leads to high bioavailability and efficient absorption.

Sources: Red meat, poultry, and seafood like clams and oysters are rich sources.
Absorption: The body has a dedicated absorption pathway for heme iron, which is minimally affected by other foods. Absorption rates typically range from 15% to 35%.
Advantages: Its high bioavailability makes it an effective source for increasing iron levels. It can also enhance the absorption of non-heme iron when consumed together, known as the "meat factor".

Non-Heme Iron: The Plant-Based and Fortified Form

Non-heme iron is more prevalent, found in plants and fortified foods. Its absorption is less efficient and more complex, influenced by dietary components.

Sources: Legumes, leafy greens, nuts, seeds, fortified grains, and eggs are good sources of non-heme iron.
Absorption: Non-heme iron requires conversion in the digestive tract and is highly sensitive to other dietary components. Absorption rates are typically lower, ranging from less than 2% to 20%.
Enhancers and Inhibitors: Vitamin C enhances non-heme iron absorption, while phytates in grains and legumes, and polyphenols in tea and coffee, can inhibit it.

Comparison of Heme and Non-Heme Iron

Understanding the differences is crucial for managing iron intake. The table below summarizes key distinctions.


Feature	Heme Iron	Non-Heme Iron
Source	Animal-based foods (meat, poultry, seafood)	Plant-based foods (legumes, nuts, greens) and fortified products
Absorption Rate	High (15–35%)	Low (less than 17%)
Absorption Mechanism	Absorbed intact via a dedicated pathway; minimally affected by other foods	Affected by dietary enhancers (Vitamin C) and inhibitors (phytates, tannins)
Main Advantage	High bioavailability for efficient iron uptake	Abundant in a wide range of foods; suitable for vegetarian diets with proper planning
Example Sources	Beef, liver, clams, chicken	Spinach, lentils, beans, fortified cereals

Practical Dietary Strategies

A balanced diet provides both iron types. For plant-based diets, strategic planning is needed. Pairing non-heme sources with vitamin C-rich foods enhances absorption. Limiting coffee, tea, or excessive dairy with meals can help, as they might hinder non-heme iron absorption. Including a small amount of meat with a plant-based meal, the “meat factor,” can boost non-heme iron absorption. Preparation methods like soaking and sprouting legumes can also improve non-heme iron availability.

Conclusion

The existence of two types of iron, heme and non-heme, reflects the body's varied approach to nutrient processing from different sources. Heme iron from animal products is highly bioavailable, while non-heme iron from plants and fortified foods is more sensitive to dietary factors. Understanding these differences helps in optimizing iron intake and preventing deficiency. Strategic dietary choices, such as pairing non-heme sources with vitamin C and managing inhibitor intake, are key to maintaining optimal iron levels for overall health, regardless of dietary choices.

Dietary Iron: A Review of Efficacy, Safety and Tolerability

Frequently Asked Questions

The two types of dietary iron are heme and non-heme. Heme iron is found exclusively in animal products like meat, poultry, and seafood. Non-heme iron is found in plant-based foods, such as legumes, nuts, and leafy greens, as well as in iron-fortified products.

Heme iron is significantly better absorbed by the body than non-heme iron. Heme iron has a higher bioavailability, with absorption rates between 15% and 35%, compared to non-heme iron, which is absorbed at a much lower rate.

You can significantly increase your absorption of non-heme iron by consuming it with a source of vitamin C, such as citrus fruits, bell peppers, or broccoli. Cooking with a cast-iron pan can also add non-heme iron to your food.

Certain foods and drinks can inhibit iron absorption, particularly non-heme iron. This includes phytates found in whole grains and legumes, polyphenols in tea and coffee, and calcium found in dairy products and supplements.

Yes, vegetarians and vegans should be mindful of their iron intake because they only consume non-heme iron, which is less efficiently absorbed. They can meet their iron needs by focusing on consuming a variety of iron-rich plant foods and regularly pairing them with vitamin C.

Cooking can affect iron. While moderate cooking doesn't significantly impact non-heme iron, baking and prolonged frying have been shown to reduce heme iron absorption. Cooking with cast iron is an effective way to introduce more non-heme iron into your food.

Iron is crucial for many bodily functions. It is a key component of hemoglobin, which transports oxygen in red blood cells throughout the body. Iron also aids in energy production, supports a healthy immune system, and contributes to proper brain function.