Iron is an essential mineral that is vital in maintaining energy levels, supporting immunity, and ensuring overall health[1]. Despite its importance, iron is often misunderstood, particularly regarding the two types found in our diet: heme and non-heme iron. These forms differ in their sources, absorption rates, and how they interact with the body.
This blog explores the differences, benefits, and best sources of both heme and non-heme iron, offering practical tips to enhance absorption and ensure a balanced iron intake.
Key Takeaways
- • Iron is categorised into two main forms—heme iron, found in animal-based foods, and non-heme iron, sourced from plants and fortified foods.
- • Heme iron has superior absorption (15–35%) and is less influenced by dietary inhibitors, while non-heme iron (less than 17%) benefits from enhancers like Vitamin C to boost bioavailability.
- • Heme iron supplements offer high absorption, making them suitable for individuals with significant deficiencies, while non-heme iron supplements provide plant-based alternatives ideal for vegetarians and vegans when paired with absorption enhancers like Vitamin C.
Types of Iron: Heme Iron and Non-Heme Iron
Iron, a critical nutrient for the human body, is categorised into two main types: heme iron and non-heme iron[1]. These types differ in their sources, absorption rates, and roles in maintaining overall health.
Heme Iron
Heme iron, primarily found in animal-based foods like meat, poultry, and fish, is structurally similar to haemoglobin, allowing for efficient absorption due to its high bioavailability[2]. More than 95% of functional iron in the human body exists as heme iron, making it crucial for oxygen transport and energy production. Heme iron is directly absorbed by small intestinal enterocytes without modification, bypassing inhibitors that typically affect non-heme iron absorption. Despite accounting for only one-third of dietary iron intake in Western diets, heme iron contributes to two-thirds of the body’s total iron stores, highlighting its superior absorption and utilisation. This essential nutrient not only supports haemoglobin and myoglobin synthesis but also plays a critical role in various enzymatic reactions and cellular functions, impacting overall physiological health and disease prevention[8].
Foods containing heme iron[3]:
- • Red meat: Beef, lamb, and pork.
- • Liver: A concentrated source of iron and other essential nutrients.
- • Poultry: Chicken and turkey, particularly dark meat.
- • Shellfish: Clams, oysters, and mussels.
- • Fish: Tuna, salmon, and mackerel.
Those who consume animal products and have increased iron needs, such as individuals recovering from surgery or illness, may benefit from including heme iron-rich foods in their diet.
Non-Heme Iron
Non-heme iron is found in plant-based and fortified foods[1]. It requires enhancers like Vitamin C for effective absorption[3], making it particularly important for vegetarians, vegans and those avoiding animal products.
Best sources of non-heme iron
- • Leafy greens: Spinach, kale, and Swiss chard.
- • Legumes: Lentils, chickpeas, and black beans.
- • Nuts and seeds: Almonds, cashews, sunflower seeds, and pumpkin seeds.
- • Fortified cereals: Breakfast cereals are enriched with iron to combat deficiencies.
Heme Iron Vs. Non-Heme Iron
Heme iron and non-heme iron, the two primary forms of dietary iron, differ significantly in their sources, absorption, and impact on health. Understanding these differences is key to tailoring your diet to meet your iron needs effectively.
1. Absorption
- • Heme Iron:
- • Non-heme Iron:
Found in animal-based foods, heme iron has high bioavailability, with an absorption rate of 15–35%[2]. It is easily absorbed directly by the body without the need for dietary enhancers, making it an efficient source of iron. However, calcium can inhibit the absorption of heme iron[5].
Found in plant-based and fortified foods, non-heme iron has a lower absorption rate of 17% or less. Its absorption is influenced by enhancers such as vitamin C and citric acid, which significantly improve bioavailability[2]. However, inhibitors like calcium (in dairy), phytates (in whole grains and legumes), and tannins (in tea and coffee) can hinder its absorption, requiring careful dietary planning for optimal utilisation[5][6].
2. Structure
- • Heme Iron:
- • Non-heme Iron:
Heme iron has a distinct structure that enhances its absorption. It consists of an iron atom centrally bound within a porphyrin ring—a large, stable, and planar structure composed of four interconnected pyrrole molecules. This configuration mirrors that of haemoglobin, allowing the iron to efficiently alternate between ferrous (Fe²⁺) and ferric (Fe³⁺) states, supporting oxygen transport and energy metabolism. The porphyrin ring protects the iron and facilitates its direct uptake in the small intestine, making heme iron a highly bioavailable source of iron for the body[7].
Non-heme iron exists in a simpler, inorganic form as either ferric (Fe³⁺) or ferrous (Fe²⁺) ions and lacks the protective porphyrin ring. It is primarily found in plant-based foods, fortified products, and dairy. Due to its free ionic form, non-heme iron is less soluble and more prone to binding with absorption inhibitors like phytates, polyphenols, and calcium. This reduces its efficiency of absorption in the small intestine, often requiring enhancers like vitamin C to convert ferric iron to the more readily absorbed ferrous form[8].
The key structural difference lies in the presence of the porphyrin ring in heme iron, which shields the iron atom and promotes direct absorption. In contrast, non-heme iron’s unbound ionic form is more reactive and vulnerable to inhibitors, leading to lower bioavailability. This structural contrast explains why heme iron is absorbed more efficiently than non-heme iron.
Benefits and Drawbacks of Heme Iron and Non-Heme Iron
Heme Iron:
Benefits of Heme iron:
- • Heme iron is easily absorbed by the body due to its porphyrin ring structure, bypassing many dietary inhibitors and making it ideal for meeting daily iron needs[2].
- • Heme iron directly supports haemoglobin and myoglobin production, aiding oxygen transport and energy metabolism essential for physical and cognitive functions[9].
- • Heme iron absorption is less affected by dietary inhibitors like phytates and polyphenols, ensuring consistent iron uptake even with diverse diets[10].
Drawbacks of heme iron:
- • Heme iron is only found in animal-based foods, making it inaccessible to vegetarians and vegans, which increases the risk of iron deficiency.
- • Ethical concerns and environmental impacts of animal farming, including resource consumption and greenhouse gas emissions, may deter consumption.
- • Excessive intake of heme iron, especially from red and processed meats, has been linked to higher risks of heart disease and certain cancers[11].
Non-heme Iron:
Benefits of Non-heme iron:
- • Non-heme iron is abundant in plant-based foods like legumes, grains, nuts, and leafy greens, making it suitable for vegetarians, vegans, and plant-based diets[3].
- • It is widely included in fortified foods (e.g., cereals, bread, and plant-based milks), offering an easy and accessible way to improve iron intake and combat deficiencies[3].
Drawbacks of Non-heme iron:
- • Non-heme iron has a lower absorption rate, requiring higher dietary intake to meet daily iron needs, especially during periods of increased demand.
- • Non-heme iron absorption is easily hindered by inhibitors like phytates, calcium, and tannins, making strategic pairing with enhancers like vitamin C essential.
- • Non-heme iron may not adequately address severe iron deficiencies, sometimes necessitating medical intervention or supplementation for effective treatment.
Health Implications
Maintaining a balance between heme and non-heme iron prevents iron deficiency and ensures overall health. Heme iron offers a reliable source for immediate needs, while non-heme iron provides an essential alternative for plant-based diets. Incorporating enhancers and minimising inhibitors can help optimise iron intake, ensuring long-term health and well-being.
By understanding these differences, you can make informed dietary choices that suit your lifestyle and nutritional needs.
Should You Consider Iron Supplements?
Iron supplements can be an effective way to address iron deficiencies, especially when diet alone isn’t enough. Whether you’re recovering from anaemia, experiencing fatigue, or have dietary restrictions, iron supplements provide a tailored solution to meet your needs. Here’s what you should know:
Heme Iron Supplements: High Absorption and Efficiency
These are ideal for individuals with significant iron needs, such as those recovering from surgery, managing anaemia, or dealing with heavy menstrual cycles[1]. A clinical study comparing the absorption of heme-bound iron and non-heme iron (inorganic ferrous sulfate) highlighted the effectiveness and tolerability of heme iron supplementation. In this study, ten healthy adults consumed 18 mg of elemental heme iron from cooked bovine blood soup and, after a washout period, ingested the same dose of inorganic ferrous sulfate. Results showed that heme iron increased serum iron levels by 18.5 µg/dL, while ferrous sulfate led to a 37.9 µg/dL increase. However, this difference was not statistically significant, indicating comparable absorption between the two forms. Notably, participants reported no gastrointestinal side effects from heme iron, unlike the discomfort often associated with non-heme iron supplements. These findings suggest that heme iron is a well-tolerated and effective alternative for individuals who struggle with the side effects of traditional iron therapy, providing a safer and more accessible option for managing iron deficiency anaemia [13].
Non-heme Iron Supplements: A Plant-Based Alternative
Non-heme iron supplements are a great plant-based option for vegetarians, vegans, or anyone avoiding animal products. However, they are not absorbed by the body as efficiently as heme iron. Research shows that pairing non-heme iron with vitamin C can significantly improve its absorption.
A study involving 12 participants explored how vitamin C affects non-heme iron absorption from complete meals. The participants followed three diet phases: a regular diet, a high-vitamin C diet (HC), and a low-vitamin C diet (LC). Although the vitamin C intake in the HC diet (247 mg/day) was five times higher than the LC diet (51 mg/day), iron absorption only increased slightly—from 4.57% to 7.69%. This increase was smaller than what’s typically seen in studies focused on single meals[14].
Further analysis found that while vitamin C helps convert ferric iron (Fe³⁺) into the easier-to-absorb ferrous form (Fe²⁺), other nutrients like phosphorus can limit this benefit. This means that simply adding vitamin C may not be enough if your diet includes inhibitors like phosphorus[14].
Key Tips for Safe and Effective Supplementation
- • Always seek advice from a healthcare expert to understand the correct dosage and type of supplement. Stick to 17 mg or less daily unless directed by a doctor. Higher doses should only be taken under medical supervision[12].
- • Supplements are most effective when combined with an iron-rich diet tailored to your preferences and health goals.
- • By choosing the right iron supplement and using it mindfully, you can effectively address deficiencies and maintain healthy iron levels to support your energy, immunity, and overall well-being.
Conclusion
Iron is a crucial nutrient that supports energy levels, immunity, and overall health. The differences between heme and non-heme iron—particularly in absorption and sources—are vital for making informed dietary choices.
At Nature’s Fix, we offer a wide range of iron supplements including heme and non-heme options, sourced from various trusted brands to support your journey towards optimal health.
FAQs
1. What are heme and non-heme iron?
Heme iron is found in animal-based foods like meat, poultry, and fish, while non-heme iron comes from plant-based foods such as nuts, spinach, lentils, and fortified cereals. The key difference lies in their absorption rates and sources[3].
2. Heme iron vs non-heme iron absorption: Which is better?
Heme iron is absorbed more efficiently (15–35%) than non-heme iron (less than 17%)[2]. Non-heme iron absorption can be improved by pairing it with Vitamin C-rich foods like oranges or peppers[3].
3.What is the Recommended Daily Iron Intake?
The recommended iron intake varies by age and gender to meet individual nutritional needs. Here’s an overview of the daily iron requirements[12]:
- • Men aged 19 and over: 8.7mg per day.
- • Women aged 19 to 49: 14.8mg per day due to the additional iron loss during menstruation
- • Women aged 50 and over: 8.7mg per day unless they are still menstruating, in which case they require 14.8mg per day’
References
1 – https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/
2 – https://www.ncbi.nlm.nih.gov/books/NBK448204/
3 – https://www.redcrossblood.org/donate-blood/blood-donation-process/before-during-after/iron-blood-donation/iron-rich-foods.html
4 – https://www.ncbi.nlm.nih.gov/books/NBK540969/
5 – https://ajcn.nutrition.org/article/S0002-9165%2823%2929606-9/fulltext
6 – https://nutritionsource.hsph.harvard.edu/anti-nutrients/
7 – https://pmc.ncbi.nlm.nih.gov/articles/PMC4045156/
8 – https://pmc.ncbi.nlm.nih.gov/articles/PMC3967179/
9 – https://lpi.oregonstate.edu/mic/minerals/iron
10 – https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/iron-absorption
11 – https://www.sciencedirect.com/science/article/pii/S0002916522046391
12 – https://www.nhs.uk/conditions/vitamins-and-minerals/iron/
13 – https://ashpublications.org/blood/article/110/11/3752/58411/Iron-Absorption-Comparison-of-Oral-Heme-Bound-Iron
14 – https://ajcn.nutrition.org/article/S0002-9165%2823%2906453-5/fulltext
