Iron is an essential micronutrient that must be consumed in recommended doses to maintain healthy body functions. An adult human body needs about 7-18mg of iron per day, which increases to about 27mg/ day in special situations like pregnancy. Adequate doses of iron must be obtained from the dietary sources to ensure health and wellness. However, certain dietary factors or diseases can greatly compromise the dietary ingestion of iron. In all such cases, required doses of iron must be consumed from supplements.
Types of Dietary Iron:
Iron from dietary sources is categorized into 2 types, heme iron and non- heme iron.
- Heme Iron: is the preferred form of iron. It is mainly obtained from animal sources such as fish, poultry, seafood, and red meat. Most of the iron present in human body (about 95%) is heme.
- Non-Heme Iron: iron is plant-based It is abundantly present in nuts, fruits, vegetables, seeds, beans, and grains. Non-heme iron is also found in dairy products, eggs, most iron supplements, fortified foods, and miscellaneous sources (such as cooking utensils, water, soil etc.)
Key Differences Between Heme Iron & Non-Heme Iron:
The chemical structure and metabolism of non-heme iron is fairly different from heme iron. Key differences are listed below:
- Absorption: Heme iron is readily absorbed by the body. Therefore is considered a great source of dietary iron. Non-heme iron on the other hand is not as easily absorbed and is not a preferred source of dietary iron. According to research studies, only 2-10% of the non-heme dietary iron is absorbed by the human body as opposed to about 20-40% of the heme iron.
- Iron metabolism: Dietary heme iron is absorbed by the body without any modification, which is why foods and supplements containing heme iron are generally well tolerated. Non-heme dietary iron on the other hand must be converted into a usable form to allow absorption. The breakdown of non-heme iron often produces reactive free ions that may lead to gastrointestinal issues such as cramps, bloating, diarrhea, and indigestion.
- Dietary Source: Plants only contain non-heme iron. Animal sources contain both heme iron (40-45%) and non heme iron (55 – 60%).
- Factors affecting absorption: The absorption of heme iron in the body is independent of foods; absorption of non-heme iron on the other hand is greatly dependent on the meal composition. For example, rice, citrus fruits/ juices, and corn can greatly increase the absorption of non-heme iron by the body. Consumption of milk, coffee or tea with meals can greatly decreases the absorption of non-heme dietary iron. Calcium intake can decrease the absorption of both heme and non-heme iron and therefore, should be avoided by people who are suffering from iron deficiency.
- Iron Supplementation: Heme iron is bound to a hemoglobin molecule. Non-heme iron comes in many different types and is usually bound to inorganic molecule such as salt or sugar. Non-heme iron includes; ferrous sulphate, ferrous fumarate, ferrous gluconate, Polysaccharide Iron Complex. Non-heme iron may come in tablet, capsule or even liquid form. This generally does not make a difference in the absorption process.
- Insufficient Intake and impact on health: Research and clinical studies indicates that low or inadequate consumption of iron is linked to serious health issues, such as porphyrias, anemia, and Alzheimer’s disease.
- Concentration in different tissues: More than 80% of the heme in the human body is concentrated in red blood cells, remaining 15-20% heme is present in liver and other tissues
Why is it important to understand the difference between heme and non-heme iron?
The biological differences between heme and non-heme iron can play a big role in certain circumstances. Some of these are listed below:
- Since plant sources do not yield readily absorbable iron; vegetarians tend to have a higher risk of developing iron deficiency. Health Canada suggests that vegetarians are to increase their intake of dietary iron or consume an iron supplement such as OptiFer.
- Women of reproductive age group and growing children are also at risk of developing iron deficiency, as recommended iron requirement exceeds the dietary iron intake.
- Certain diseases or health issues can alter the metabolism of heme and non-heme iron. For example, someone with irritable bowel syndrome (IBS) has a harder time absorbing nutrients. A heme iron with its high absorption profile would help.
In conclusion, it is important to consume a well-balanced nutritious diet to maintain optimal health. As discussed, certain factors and dietary combinations can impact the absorption of dietary iron. It is highly recommended to use the knowledge of the heme and non-heme iron to make informed decisions about your health. For instance, if you are at risk of developing iron deficiency, increase your intake of heme iron or reduce the intake of calcium to maximize the absorption of dietary iron.
- Hooda, J., Shah, A., & Zhang, L. (2014). Heme, an essential nutrient from dietary proteins, critically impacts diverse physiological and pathological processes. Nutrients, 6(3), 1080–1102. https://doi.org/10.3390/nu6031080