Not all iron is created equally, and if you have an iron imbalance, you should carefully consider which iron is best for your health. Your body recognizes the difference between heme and nonheme iron sources and will absorb each type differently. These types are easy to identify in your daily diet. Heme iron comes from animals, and nonheme iron comes from plants. Here is everything else you need to know about the differences between heme and nonheme iron and how each can affect your health.
What Is Heme Iron?
Heme iron is the type of iron found in blood and muscle. Present in animal foods like red meats, fish, and poultry, heme iron is a significant source of the absorbed iron in a typical western diet, though it only makes up about one-third of dietary iron. Heme iron gets its name from the heme protein attached to a lone iron atom. The “heme” in the blood protein hemoglobin refers to this protein-bound form of iron.
Health Benefits of Heme Iron
On average, the human body absorbs about 15% to 35% of heme iron consumed. While the exact mechanism of absorption is unclear, it is clear that the body absorbs heme iron more readily than nonheme iron. However, it’s important to note that heme iron introduces the negative health effects associated with consuming animal products.
Health Risks of Heme Iron
While iron is an essential mineral, the rapid absorption of heme iron is not always a good thing. Keeping the right iron balance is critical. Too little iron puts you at risk for developing iron deficiency anemia; too much can increase oxidative stress. While these concerns can exist with nonheme iron, there are additional health concerns linked directly to heme iron, including the risk of stroke, coronary heart disease, several types of cancer, and gastrointestinal side effects.[3, 4, 5]
Sources of Heme Iron
Heme iron only exists in animal products or animal-based iron supplements. These heme iron supplements are available as powders, tablets, capsules, and even drinks. Heme iron-rich foods include oysters, beef liver, and sardines.
What Is Nonheme Iron?
Nonheme iron is iron found in plant foods like green leafy vegetables, beans, and nuts. Nonheme iron is not combined with a heme protein, and this difference is the reason for the body’s reduced ability to absorb nonheme iron. Slower absorption allows you to eat more iron-rich plants without worrying about iron toxicity.
Health Benefits of Nonheme Iron
Nonheme iron is the iron found in plants, and plant foods are inherently healthier than animal foods. Additionally, because nonheme iron is absorbed at a rate of 2% to 20%, toxic iron overload is less likely. Maintaining adequate levels of iron is a delicate balance. Your body is significantly better at moderating the absorption of nonheme iron. Heme iron, on the other hand, can bypass the body’s attempts to control iron absorption. Since you have no way of eliminating excess iron from the body, this gives nonheme iron a significant advantage over heme iron.[1, 8]
Likewise, consuming plant-based foods provides an array of powerful nutrients, antioxidants, and phytochemicals to support your overall health, not just your iron status. Nonheme iron is also less likely to cause health concerns for your heart, unlike meat.
Disadvantages of Nonheme Iron
Bioavailability is the main difference between heme and nonheme iron. Nonheme iron is absorbed at a lower rate than heme iron. However, in this case, its weakness is a strength in disguise. Nonheme iron poses a lower risk of causing iron toxicity, even when consumed in large amounts. Your body allows the iron to pass through the digestive system for elimination.
Best Sources of Nonheme Iron
Plant-based food is the best source of nonheme iron. You can boost your iron intake by eating more iron-rich vegan foods like spinach, lentils, and pumpkin seeds. Also, taking with vitamin C can enhance the absorption of iron. Some supplements contain only nonheme iron, but they are far less common than their heme supplement counterparts.
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- West, Adrian R., and Phillip S. Oates. “Mechanisms of Heme Iron Absorption: Current Questions and Controversies.” World Journal of Gastroenterology. (2008): 4101–4110.
- Morsen, E.R. “Iron nutrition and absorption: dietary factors which impact iron bioavailability.” Journal of the American Dietetic Association (1988): 786-790.
- Kaluza J., Wolk A., Larsson S.C. “Heme iron intake and risk of stroke: a prospective study of men. Stroke.” (2013):334-339.
- Yang, W., Li, B., Dong, X., et al. “Is heme iron intake associated with risk of coronary heart disease? A meta-analysis of prospective studies.” Eur J Nutr. (2014): 395.
- Nadia M. Bastide, Fabrice H.F. Pierre and Denis E. Corpet. “Heme Iron from Meat and Risk of Colorectal Cancer: A Meta-analysis and a Review of the Mechanisms Involved.” Cancer Prev Res February. (2011): 177-184.
- “Office of Dietary Supplements – Dietary Supplement Fact Sheet: Iron.” National Institutes of Health. U.S. Department of Health and Human Services, n.d. Web. 19 Apr. 2017.
- Gulec, Sukru, Gregory J. Anderson, and James F. Collins. “Mechanistic and Regulatory Aspects of Intestinal Iron Absorption.” American Journal of Physiology – Gastrointestinal and Liver Physiology 307.4 (2014): G397–G409.
- Cook, J.D. “Adaptation In Iron Metabolism.” American Journal of Clinical Nutrition 51.2 (2017): 301-308. Web. 21 Apr. 2017.