Type of Nutrient and its Source
Iron is an essential mineral that is vital to the human body. The body needs iron to produce hemoglobin, a protein in red blood cells that carries oxygen from the lungs to the body’s tissues. Iron is also necessary for many other bodily functions, such as DNA synthesis and energy production. Iron is found in various foods, including red meat, poultry, fish, beans, lentils, tofu, spinach, and fortified cereals. Heme iron, found in animal products, is more easily absorbed by the body than non-heme iron, located in plant-based foods (Petry et al., 2016). However, consuming vitamin C along with non-heme iron can increase absorption. Iron deficiency is a common nutritional deficiency, particularly among women and children. Symptoms of iron deficiency include fatigue, weakness, pale skin, and shortness of breath. Severe iron deficiency can lead to anemia, a condition in which the body does not have enough red blood cells to carry oxygen to its tissues.
Common Name and Scientific Name
The common name for the nutrient is iron, and its scientific name is Fe (from the Latin word Ferrum).
Purpose in the Body
Iron is a mineral and is not water or fat-soluble. Iron is essential for the formation of hemoglobin in red blood cells, which transports oxygen from the lungs to the rest of the body. It also affects immune system function, cognitive development, and energy production (Murray-Kolb & Beard, 2018). Iron is involved in the production of myoglobin, a protein that stores oxygen in muscles and is required for the synthesis of certain hormones and connective tissues. It is also necessary for the proper function of enzymes involved in DNA synthesis and repair and the metabolism of drugs and other substances.
Body Metabolism of the Nutrient
Iron is primarily absorbed in the small intestine. The process of iron absorption is complex and regulated by several proteins and enzymes. Iron can be present in two forms: heme and non-heme iron. Heme iron, found in animal-based foods such as red meat, poultry, and fish, is more easily absorbed than non-heme iron, which is found in plant-based foods such as beans, lentils, and leafy greens. Once ingested, heme iron is released from food proteins and transported to the small intestine, which is absorbed into the enterocytes or cells lining the intestine (Tussing-Humphreys & Nemeth, 2018). Heme iron is then transported into the bloodstream by a protein called ferroportin, regulated by the hormone hepcidin.
Non-heme iron is absorbed through a different mechanism. It must first be converted to a more absorbable form by stomach acid and enzymes and then transported into the enterocytes by a protein called divalent metal transporter 1 (DMT1). From there, non-heme ferroportin can transport the non-heme iron cell membrane through a ferrite bloodstream.
Excess iron is stored in the liver, spleen, and bone marrow, where it can be used to produce red blood cells and other necessary functions. The body can excrete excess iron through shedding skin, hair, and nails, as well as through blood loss during menstruation and injury. However, the body has no natural mechanism for excreting excess iron so overconsumption can lead to iron overload and toxicity.
Recommended Dietary Allowance & Dietary Reference Intake for an Adult
The Recommended Dietary Allowance (RDA) for iron varies by age and gender. For adult males aged 19-50 years, the RDA is 8 milligrams (mg) per day, while for adult females in the same age group, the RDA is 18 mg per day (Tussing-Humphreys & Nemeth, 2018). However, after menopause, the RDA for women decreases to 8 mg daily, the same as for men. Pregnant women have a higher RDA of 27 mg per day due to increased needs for fetal development.
The Dietary Reference Intake (DRI) is a broader range of nutrient intake recommendations that include the RDA as well as other measures of adequate intake, such as the Estimated Average Requirement (EAR) and the Tolerable Upper Intake Level (UL). For iron, the DRI includes an EAR of 6 mg per day for adult men and postmenopausal women and 8 mg per day for premenopausal women. The UL for iron is 45 mg per day daily, beyond which intake can lead to toxicity.
Nutrient Consumption in America
According to the National Health and Nutrition Examination Survey (NHANES) conducted by the Centers for Disease Control and Prevention (CDC), the average daily intake of iron among U.S. adults aged 20 years and older is approximately 16 mg for men and 13 mg for women (Bastide et al., 2017). However, specific populations, such as pregnant women and vegetarians, may have higher or lower intake levels. It is important to note that iron deficiency is still a common health issue, particularly among women and children, despite adequate intake levels in some populations.
Significance of Nutrients in History
Iron has played an essential role in human history, particularly in treating iron-deficiency anemia. The ancient Egyptians, Greeks, and Romans used iron-containing foods and minerals to treat anemia and fatigue. Hippocrates recommended iron-rich foods like liver and spinach to his patients.
During the Industrial Revolution in the 19th century, iron deficiency anemia became a widespread public health issue, particularly among women and children who were more likely to suffer from malnutrition (Brannon, 2021). This led to the development of iron supplementation and fortified foods to prevent and treat today; iron supplements and fortified foods remain a common strategy for managing iron deficiency anemia, although dietary changes and addressing underlying causes are also significant.
Significance in Contemporary Times
In contemporary times, there are many health claims related to iron. One of the most common is the promotion of iron-rich diets or supplements for athletic performance, as iron is involved in producing energy and oxygen transport to muscles. Iron has also been linked to cognitive function, with some studies suggesting that iron deficiency may impair brain function and increase the risk of cognitive decline in older adults. However, it is essential to note that excessive iron intake can be harmful and lead to toxicity, particularly in people with hereditary hemochromatosis or other genetic disorders affecting iron metabolism. Iron supplements and fortified foods should only be used under the guidance of a healthcare professional, and excessive intake should be avoided.
History of Discovery and Marketing of the Nutrient
Iron has been recognized as an essential nutrient for centuries, and its discovery can be traced back to ancient civilizations. However, the isolation of iron in its pure form only occurred in the 18th century, when chemists began experimenting with the metal and its compounds. The marketing of iron supplements and fortified foods began in the early 20th century, as the prevalence of iron-deficiency anemia became a growing public health concern (Brannon, 2021). In the 1920s, Geritol, a multivitamin and mineral supplement that contained iron, was marketed as a treatment for fatigue and weakness, particularly among women. Fortified foods, such as iron-fortified breakfast cereals, were also developed and promoted to prevent anemia and promote health.
In recent years, there has been controversy surrounding the use of ousingplements and fortified foods, mainly in high-income countries where iron deficiency anemia is less common. Some studies have suggested that excessive iron intake may increase the risk of chronic diseases, such as disease and cancer, while others have found no such association.
Three Research Articles that Support and Dispute the Health Claims Related to Iron
Support: Iron supplementation improves physical performance in women of reproductive age. This randomized controlled trial found that iron supplementation improved physical performance, including endurance and energy levels, in women with iron deficiency anemia. (Petry et al., 2016)
Dispute: High iron intake may increase the risk of chronic diseases. This systematic review and meta-analysis found that a high dietary iron intake was associated with an increased risk of type 2 diabetes and colorectal cancer but not a cardiovascular disease or mortality. (Bastide et al., 2017)
Support: Iron supplementation may improve cognitive function in children with iron deficiency anemia. This systematic review and meta-analysis found that iron supplementation improved cognitive function, including attention, memory, and learning, in children with iron deficiency anemia. (Murray-Kolb & Beard, 2018)
References
Brannon, P. M. (2021). Iron supplementation during pregnancy: Weighing the evidence. Nutrients, 13(2), 623. doi: 10.3390/nu13020623 https://www.mdpi.com/2072-6643/13/2/623
Bastide, N. M., Pierre, F. H., & Corpet, D. E. (2017). Heme iron from meat and risk of colorectal cancer: a meta-analysis and a review of the mechanisms involved. Cancer Prevention Research, 10(2), 93-101
Murray-Kolb, L. E., & Beard, J. L. (2018). Iron treatment normalizes cognitive functioning in young women. American Journal of Clinical Nutrition, 107(5), 763-77
Petry, N., Olofin, I., Hurrell, R. F., & Boy, E. (2019). The potential of iron‐fortified maize meal to reduce the prevalence of iron deficiency in South African women. Advances in Nutrition, 7(1), 137–146.
Tussing-Humphreys, L. M., & Nemeth, E. (2018). Iron metabolism and iron deficiency anemia: Implications for the athlete. Current Sports Medicine Reports, 17(6), 179–186. doi: 10.1249/JSR.0000000000000496 https://journals.lww.com/acsm-csmr/Fulltext/2018/06000/Iron_Metabolism_and_Iron_Deficiency_Anemia__.3.aspx
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