Updated: Nov 20, 2019
Iron is a key element in metabolism in all living organisms; this includes both humans and pathogens (i.e. bacterial infections). Older people need about 8 mg of iron in the diet daily to maintain adequate stores under normal conditions. Older age, alone, does not increase the risk of iron deficiency. Iron deficiency is most often associated with intestinal blood loss in older adults. This is because 0.5 mg of iron is in only 1 mL of blood.
How is iron maintained within the body under normal conditions?
Hemoglobin, the primary protein in red blood cells, contains 2/3 of the body’s iron, and its job is to carry oxygen in blood to all the tissues of the body. Most of the body’s iron is recycled through the senescence of red blood cells. That is, red blood cells live for about 90 days and then are recycled in the spleen, iron and all. This is accomplished when macrophages (large white blood cells) engulf retiring red blood cells in the spleen. About 20 mg of iron is recovered daily in this method, and the iron is stored in ferritin (an iron-storing protein) or transported in transferrin (an iron-transporting protein).
Recommended Dietary Allowance
19+ years: 8 mg/d
19-50 years: 18 mg/d
51+ years: 8 mg/d Pregnancy: 27 mg/d
Lactation: 9 mg/d
Regular, intense exercise (i.e. marathon training)
Increase iron intake needs by 30%
Upper Limit (for everyone including pregnant): this is the maximum amount deemed safe for daily iron intake
What is Heme Iron?
Heme iron is the type of iron found in meats and animal products. Heme iron is the most bioavailable type of iron; it is less impacted by other dietary enhancers (vitamin C) and inhibitors (calcium) than non-heme iron. Chicken is not a great source of iron - this could be a result of how chickens are commercially raised in first world countries. Turkey, beef, and organ meats are some of the best sources of heme iron.
The science: Heme is an iron-containing compound, and hemoproteins are iron-dependent proteins. Examples are hemoglobin (found within the blood), myoglobin (found within muscle), and neuroglobin (found within nervous tissue/brain) and are responsible for the transport of oxygen and storage of iron. Hemoglobin and myoglobin is the iron form found in meat, poultry, eggs, and fish. Heme enzymes are involved in DNA replication/repair as well as electron transfer (ATP production, cytochromes including cytochrome P450, oxidase). Iron-sulfur cluster proteins are involved in energy production (NADH dehydrogenase/Kreb Cycle). As detailed here, iron plays a huge role in oxygen and energy levels within the body; this makes a lot of sense when reviewing the signs and symptoms of iron deficiency reviewed further down this article.
What is Non-Heme Iron?
Non-heme proteins require iron as a cofactor and responsible for iron transport/storage (i.e. ferritin, transferrin). Dietary intake of non-heme iron includes plant sources such as tomatoes, broccoli, spinach, CHOCOLATE (capitalize to emphasize enthusiasm), dairy, iron salts, iron supplements, and fortified foods (i.e. cereals, breads) and is enhanced by vitamin C (i.e. in many fruits and vegetables such as citrus, strawberries, bell peppers, tomatoes) as well as inhibited by phytic acid and polyphenol compounds (i.e. found in tea and coffee).
What is Iron Deficiency?
Three types of iron deficiency are detailed here. The first two are traditional ideas of iron deficiency.
Iron Deficiency – “an inadequate supply of iron to cells following depletion of the body’s reserves” (Linus Pauling, 2019). Anemia will not be present. At this stage, iron deficiency may be under-diagnosed.
Iron Deficiency Anemia – “Microcytic anemia occurs when body iron stores are so low that hemoglobin synthesis and red blood cell formation are severely impaired” (Linus Pauling, 2019).
Functional Iron Deficiency – iron has been sequestered into the reticuloendothelial system (also known as the mononuclear phagocyte system) so available iron is inadequate. Read on for how why this happens. The Host Defense Mechanism creates a condition of iron deficiency when the body creates an inaccessibility of existing stores of iron to the body with the intention of protecting the body during illness, inflammation, and chronic disease. When this mechanism takes place during illness, the body withdraws iron into the tissues to make it unavailable to pathogens. This is done with the increase in hepcidin, a key regulator in systemic iron homeostasis. In conditions of inflammation, hepcidin is upregulated due to its antimicrobial role by limiting iron availability to invading microorganisims. Hepcidin inhibits iron absorption, promotes cellular sequestration, and reduces iron bioavailability. While pathogens require iron to grow and spread, so does the host in order to boost the immune system to fight infection (in the creation of lymphocytes).
Levels of Iron Deficiency
Iron deficiency is manifested in different levels of severity. The following is iron deficiency in its progressive stages from least to most severe.
Storage Iron Depletion – stores are depleted but functional iron supply is not limited
Early Functional Iron Deficiency – inadequate supply of iron to tissues (impairs erythropoiesis, the making of new red blood cells)
Iron-Deficiency Anemia – decreased hemoglobin, microcytic hypochromic anemia (small, pale red blood cells as seen under a microscope); inadequate iron to support RBC production
What are the Common Comorbidities of Iron Deficiency?
Common conditions associated with iron deficiency are obesity, chronic kidney disease, dialysis, and inflammaging and are described below.
The obese are specifically at risk for functional iron deficiency, and blood laboratory tests need to be looked into differently. Obesity causes a chronic low grade inflammation which may lead to a functional iron deficiency.
Higher hepcidin blood levels have been noted in obese people related to chronic inflammation which sequesters iron and decreases iron absorption. The Soluble Transferrin Receptors test, which will be elevated, is recommended to confirm iron deficiency in obesity. Ferritin is a questionable biomarker due to its ability to increase with the inflammatory state of obesity. Weight loss may lower serum hepcidin concentration and improve iron status.
Chronic Kidney Disease (non-dialysis)
Iron deficient in chronic kidney disease has a ferritin cutoff value of <100 which differs from those with normal kidney function.
The ferritin cutoff value with those undergoing dialysis treatments is <200. The increase in ferritin is the result of the high likeliness of upregulation in chronic inflammation of (Macdougall et al., 2016).
Inflammaging is the term representing the theory that aging creates a state of low grade infammation. As a result, the elderly may have an increased hepcidin blood level and subsequent decreased iron absorption. The soluble transferrin receptors index is one of the most helpful biomarkers in elderly to diagnose iron deficiency.
Risk Factors of Iron Deficiency in Older Adults
Any of the following increase one's risk to iron deficiency: blood loss (i.e. gastrointestinal bleeds, peptic ulcers), celiac disease, hypochlorhydria, atrophic gastritis, inflammatory bowel disease, obesity, gastric bypass, anemia of chronic disease, restless leg syndrome, chronic kidney disease, hemodialysis, thrombocytosis, anticoagulants
At risk for iron deficiency in others: pregnancy, lactation, infants, children, menstruation
Men and older adults are at the lowest risk of iron deficiency.
What are the Signs and Symptoms of Iron Deficiency?
-Pallor, fatigue, weakness as a result of decreased oxygen to cellular tissue.
-Low energy is due to decreased electron transfer and consequential NADH dehydrogenase function.
-Anemia presents with fatigue, rapid heart rate, palpitations, rapid breathing on exertion
-Impairment of physical work capacity due to decreased oxygen delivery, decreased myoglobin level in muscle cells, and decreased ATP synthesis/electron transport.
-Increased risk of falls, disability, and depression.
-Nails in severe iron deficiency may present with koilonychia - brittle, spoon-shaped nails.
-Mouth may present with cheilosis, taste bud atrophy, and a sore tongue.
-Pica is the consumption of non-food items (both a symptom and cause of iron deficiency). -Iron deficiency can impair thyroid metabolism and result in goiters. Heme-containing thyroid peroxidase catalyzes the iodination of thyroglobulin for the production of thyroid hormones.
Medical Nutrition Therapy/Treatment
Iron should not be supplemented to prevent iron deficiency in older adults due to iron toxicity risks which is pro-inflammatory to the body. Iron supplementation should only be given to those with diagnosed iron deficient or at high risk. Supplementation to treat iron deficiency includes oral iron, intravenous iron, and blood transfusion. Medications that can interfere is with iron absorption should be discontinued (please discuss with your prescribing doctor) which include medications that decrease stomach acidity: proton pump inhibitors (i.e. omeprazole), antacids, histamine receptor antagonists (i.e. ranitidine) (Sharma, Brannon, & Carloss, 2004). This is because the first step of iron digestion begins in the stomach in relation to the acidity of gastric juices. Chronic intake of low dose aspirin (81 mg) has also been associated iron deficiency related to blood loss which decreases iron and ferritin from a cytokine-mediated effect.
Importantly, meeting the recommend dietary allowance for iron through dietary sources should be prioritized (see above towards the top of this article for adequate daily iron intake amounts).
Balducci, L. (2003). Epidemiology of anemia in the elderly: information on diagnostic evaluation. American Geriatrics Society. 51: S2-S9.
Chernoff, R. (2014). Geriatric Nutrition: The Health Professional’s Handbook(4th ed.). Sudbury: Jones & Barlett Publishers, Inc.
Fairweather-Tait, S., Wawer, A., Gillings, R., Jennings, A., & Myint, P. (2014). Iron status in the elderly. Mechanisms of Ageing and Development, 136-137(100), 22–28. http://dx.doi.org/10.1016/j.mad.2013.11.005
Linus Pauling Institute. (2019). Micronutrients for older adults. Retrieved from http://lpi.oregonstate.edu/mic/life-stages/older-adults#disease-index.
Macdougall, Bircher, Eckardt, Obrador, Pollock, Stenvinkel, Swinkels, Wanner, Weiss, & Chertow. (2016). Iron management in chronic kidney disease: conclusions from a ‘kidney disease: improving global outcomes’ (KDIGO) controversies conference. Kidney International. https://doi.org/10.1016/j.kint.2015.10.002
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Sharma, V., Brannon, M., & Carloss, E. (2004). Effect of Omeprazole on Oral Iron Anemia. 97(9), 887–890.