Iron deficiency

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Iron deficiency
Classification and external resources
Heme b.svg
ICD-10 E61.1
ICD-9 280.9
DiseasesDB 6947
MedlinePlus 000584
eMedicine med/1188

Iron deficiency (sideropenia or hypoferremia) is one of the most common of the nutritional deficiencies.[1] Iron is present in all cells in the human body, and has several vital functions. Examples include as a carrier of oxygen to the tissues from the lungs in the form of hemoglobin, as a transport medium for electrons within the cells in the form of cytochromes, and as an integral part of enzyme reactions in various tissues. Too little iron can interfere with these vital functions and lead to morbidity and death.

The eventual consequence of iron deficiency is iron deficiency anemia where the body's stores of iron have been depleted and the body is unable to maintain levels of haemoglobin in the blood. Children and pre-menopausal women are the groups most prone to the disease.

Total body iron averages approximately 3.8 g in men and 2.3 g in women. In blood plasma, iron is carried tightly bound to the protein transferrin. There are several mechanisms that control human iron metabolism and safeguard against iron deficiency. The main regulatory mechanism is situated in the gastrointestinal tract. When loss of iron is not sufficiently compensated by adequate intake of iron from the diet, a state of iron deficiency develops over time. When this state is uncorrected, it leads to iron deficiency anemia.

Signs and symptoms[edit]

Symptoms of iron deficiency can occur even before the condition has progressed to iron deficiency anemia.

Symptoms of iron deficiency are not unique to iron deficiency (i.e. not pathognomonic). Iron is needed for many enzymes to function normally, so a wide range of symptoms may eventually emerge, either as the secondary result of the anemia, or as other primary results of iron deficiency. Symptoms of iron deficiency include:

Continued iron deficiency may progress to anaemia and worsening fatigue. Thrombocytosis, or an elevated platelet count, can also result. A lack of sufficient iron levels in the blood is a reason that some people cannot donate blood.

Causes[edit]

Though genetic defects causing iron deficiency have been studied in rodents, there are no known genetic disorders of human iron metabolism that directly cause iron deficiency.

Athletics[edit]

Possible reasons that athletics may contribute to lower iron levels includes mechanical hemolysis (destruction of red blood cells from physical impact), loss of iron through sweat and urine, gastrointestinal blood loss, and haematuria (presence of blood in urine).[4][5] Although small amounts of iron are excreted in sweat and urine, these losses can generally be seen as insignificant even with increased sweat and urine production, especially considering that athlete’s bodies appear to become conditioned to retain iron better.[4] Mechanical hemolysis is most likely to occur in high impact sports, especially among long distance runners who experience “foot-strike hemolysis” from the repeated impact of their feet with the ground. Exercise-induced gastrointestinal bleeding is most likely to occur in endurance athletes. Haematuria in athletes is most likely to occur in those that undergo repetitive impacts on the body, particularly affecting the feet (such as running on a hard road or Kendo) and hands (e.g.Conga or Candombe drumming). Additionally, athletes in sports that emphasize weight loss (ballet, gymnastics, marathon running, wrestling) as well as sports that emphasize high-carbohydrate, low-fat diets, may be at an increased risk for iron deficiency.[4][5]

Diagnosis[edit]

  • A complete blood count can reveal microcytic anemia,[6] although this is not always present - even when iron deficiency progresses to iron deficiency anaemia.
  • Low serum ferritin *see below
  • Low serum iron
  • High TIBC (total iron binding capacity), although this can be raised in cases of anaemia of chronic inflammation
  • It is possible that the fecal occult blood test might be positive, if iron deficiency is the result of gastrointestinal bleeding, although the sensitivity of the test may mean that in some cases it will be negative even with enteral blood loss

As always, laboratory values have to be interpreted with the lab's reference values in mind and considering all aspects of the individual clinical situation.

Serum ferritin can be elevated in inflammatory conditions and so a normal serum ferritin may not always exclude iron deficiency, and the utility is improved by taking a concurrent C reactive protein (CRP). The level of serum ferritin that is viewed as "high" depends on condition. For example, in Inflammatory bowel disease the threshold is 100, where as in chronic heart failure (CHF) the levels are 200.

Treatment[edit]

Before commencing treatment, there should be definitive diagnosis of the underlying cause for iron deficiency. This is particularly the case in older patients, who are most susceptible to colorectal cancer and the gastrointestinal bleeding it often causes. In adults, 60% of patients with iron deficiency anemia may have underlying gastrointestinal disorders leading to chronic blood loss.[7] It is likely that the cause of the iron deficiency will need treatment as well.

Upon diagnosis, the condition can be treated with iron supplements. The choice of supplement will depend upon both the severity of the condition, the required speed of improvement (e.g. if awaiting elective surgery) and the likelihood of treatment being effective (e.g. if has underlying IBD, undergoing dialysis or is having ESA therapy).

Examples of oral iron that are often used are ferrous sulfate, ferrous gluconate, or amino acid chelate tablets. Recent research suggests the replacement dose of iron, at least in the elderly with iron deficiency, may be as little as 15 mg per day of elemental iron.[8]

Food sources[edit]

Mild iron deficiency can be prevented or corrected by eating iron-rich foods and by cooking in an iron skillet. Because iron is a requirement for most plants and animals, a wide range of foods provide iron. Good sources of dietary iron have heme-iron as this is most easily absorbed and is not inhibited by medication or other dietary components. Three examples are red meat, poultry and insects.[9][10] Non-heme sources do contain iron, though it has reduced bioavailability. Examples are lentils, beans, leafy vegetables, pistachios, tofu, fortified bread, and fortified breakfast cereals.

Iron from different foods is absorbed and processed differently by the body; for instance, iron in meat (heme iron source) is more easily absorbed than iron in grains and vegetables ("non-heme" iron source),[11] but heme/hemoglobin from red meat has effects which may increase the likelihood of colorectal cancer.[12][13] Minerals and chemicals in one type of food may also inhibit absorption of iron from another type of food eaten at the same time.[14] For example, oxalates and phytic acid form insoluble complexes which bind iron in the gut before it can be absorbed.

Because iron from plant sources is less easily absorbed than the heme-bound iron of animal sources, vegetarians and vegans should have a somewhat higher total daily iron intake than those who eat meat, fish or poultry.[15] Legumes and dark-green leafy vegetables like broccoli, kale and oriental greens are especially good sources of iron for vegetarians and vegans. However, spinach and Swiss chard contain oxalates which bind iron making it almost entirely unavailable for absorption. Iron from nonheme sources is more readily absorbed if consumed with foods that contain either heme-bound iron or vitamin C. This is due to a hypothesised "meat factor" which enhances iron absorption.[16]

Many medicinal herbs can offer iron boosting properties to those who suffer from iron deficiency. These medicinal properties can easily be assimilated into the bloodstream as a hot water infusion (tea). Iron enhancing herbs include yellow dock, red raspberry leaf, gentian, yellowroot, turmeric, mullein, nettle, parsley, ginseng, watercress, and dandelion.[17]

Following are two tables showing the richest foods in heme and non-heme iron.[18] In both tables, foods serving size may differ from the usual 100g quantity for relevancy reasons. Arbitrarily, the guideline is set to 18 mg, which is the USDA Recommended Dietary Allowance for women aged between 19 and 50.[19]

Abstract: richest foods in heme iron
Food Serving Size Iron % Guideline
clam 100g 28 mg 155%
pork liver 100g 18 mg 100%
lamb kidney 100g 12 mg 69%
cooked oyster 100g 12 mg 67%
cuttlefish 100g 11 mg 60%
lamb liver 100g 10 mg 57%
octopus 100g 9.5 mg 53%
mussel 100g 6.7 mg 37%
beef liver 100g 6.5 mg 36%
beef heart 100g 6.4 mg 35%
Abstract: richest foods in non-heme iron
Food Serving Size Iron % Guideline
soybeans 250ml 9.3 mg 52%
raw yellow beans 100g 7 mg 39%
lentils 250ml 7 mg 39%
falafel 140g 4.8 mg 27%
soybean kernels 250ml 4.7 mg 26%
toasted sesame seeds 30g 4.4 mg 25%
spirulina 15g 4.3 mg 24%
candied ginger root 30g 3.4 mg 19%
spinach 85g 3 mg 17%

Iron deficiency can have serious health consequences that diet may not be able to quickly correct, hence an iron supplement is often necessary if the iron deficiency has become symptomatic.

Bioavailability and bacterial infection[edit]

Iron is needed for bacterial growth making its bioavailability an important factor in controlling infection.[20] Blood plasma as a result carries iron tightly bound to transferrin, which is taken up by cells by endocytosing transferring, thus preventing its access to bacteria.[21] Between 15 and 20 percent of the protein content in human milk consists of lactoferrin[22] that binds iron. As a comparison, in cow's milk, this is only 2 percent. As a result, breast fed babies have fewer infections.[21] Lactoferrin is also concentrated in tears, saliva and at wounds to bind iron to limit bacterial growth. Egg white contains 12% conalbumin to withhold it from bacteria that get through the egg shell (for this reason prior to antibiotics, egg white was used to treat infections).[23]

To reduce bacterial growth, plasma concentrations of iron are lowered in a variety of systemic inflammatory states due to increased production of hepcidin which is mainly released by the liver in response to increased production of pro-inflammatory cytokines such as Interleukin-6. This functional iron deficiency will resolve once the source of inflammation is rectified, however if not resolved it can progress to Anaemia of Chronic Inflammation. The underlying inflammation can be caused by fever,[24] Inflammatory Bowel Disease, infections, Chronic Heart Failure (CHF), carcinomas and following surgery.

Reflecting this link between iron bioavailability and bacterial growth, the taking of oral iron supplements causes a relative over abundance of iron that can alter the types of bacteria that are present within the gut. There have been concerns regarding parenteral iron being administered whilst bacteremia is present, although this has not been borne out in clinical practice. A moderate iron deficiency, in contrast, can provide protection against acute infection, especially against organisms that reside within hepatocytes and macrophages such as Malaria and TB. This is mainly beneficial in regions with a high prevalence of these diseases and where standard treatment is unavailable.

References[edit]

  1. ^ Dlouhy, Adrienne C.; Outten, Caryn E. (2013). "Chapter 8.4 Iron Uptake, Trafficking and Storage". In Banci, Lucia (Ed.). Metallomics and the Cell. Metal Ions in Life Sciences 12. Springer. doi:10.1007/978-94-007-5561-1_8. ISBN 978-94-007-5560-4.  electronic-book ISBN 978-94-007-5561-1 ISSN 1559-0836 electronic-ISSN 1868-0402
  2. ^ Wintergerst, E. S.; Maggini, S.; Hornig, D. H. (2007). "Contribution of Selected Vitamins and Trace Elements to Immune Function". Annals of Nutrition and Metabolism 51 (4): 301–323. doi:10.1159/000107673. PMID 17726308.  edit
  3. ^ Rangarajan, Sunad; D'Souza, George Albert. (April 2007). "Restless legs syndrome in Indian patients having iron deficiency anemia in a tertiary care hospital". Sleep Medicine. 8 (3): 247–51. doi:10.1016/j.sleep.2006.10.004. PMID 17368978. 
  4. ^ a b c Nielson, Peter; Nachtigall, Detlef (Oct 1998). "Iron supplementation in athletes: current recommendations". Sports Med 26: 207–216. Retrieved 7 July 2013. 
  5. ^ a b Chatard, Jean-Claude; Mujika, Iñigo; Guy, Claire; Lacour, Jean-René (Apr 1999). "Anaemia and Iron Deficiency in Athletes Practical Recommendations for Treatment". Sports Med. 4 27: 229–240. Retrieved 7 July 2013. 
  6. ^ Longmore, Murray; Ian B. Wilkinson, Supaj Rajagoplan (2004). Oxford Handbook of Clinical Medicine (6th ed.). Oxford University Press. pp. 626–628. ISBN 0-19-852558-3. 
  7. ^ Rockey D, Cello J (1993). "Evaluation of the gastrointestinal tract in patients with iron-deficiency anemia". N Engl J Med 329 (23): 1691–5. doi:10.1056/NEJM199312023292303. PMID 8179652. 
  8. ^ Rimon E, Kagansky N, Kagansky M, Mechnick L, Mashiah T, Namir M, Levy S (2005). "Are we giving too much iron? Low-dose iron therapy is effective in octogenarians". Am J Med 118 (10): 1142–7. doi:10.1016/j.amjmed.2005.01.065. PMID 16194646. 
  9. ^ Defoliart,G. 1992. Insects as Human Food. Crop Protection, 11:395-99.
  10. ^ Bukkens SGF. 1997. The Nutritional Value of Edible Insects. Ecol. Food. Nutr. Vol. 36(2–4): pp. 287–319.
  11. ^ Iron deficiency. Food Standards Agency.
  12. ^ Sesink AL, Termont DS, Kleibeuker JH, Van der Meer R (1999). "Red meat and colon cancer: the cytotoxic and hyperproliferative effects of dietary heme". Cancer Research 59 (22): 5704–9. PMID 10582688. 
  13. ^ Glei M, Klenow S, Sauer J, Wegewitz U, Richter K, Pool-Zobel BL (2006). "Hemoglobin and hemin induce DNA damage in human colon tumor cells HT29 clone 19A and in primary human colonocytes". Mutat. Res. 594 (1–2): 162–71. doi:10.1016/j.mrfmmm.2005.08.006. PMID 16226281. 
  14. ^ Iron in diet. MedlinePlus.
  15. ^ Mangels, Reed. Iron in the vegan diet. The Vegetarian Resource Group.
  16. ^ Iron. The Merck Manuals Online Medical Library.
  17. ^ [1]. Every Green Herb.
  18. ^ iron rich foods. Rich Foods.
  19. ^ Dietary Reference Intakes: Recommended Intakes for Individuals National Academy of Sciences. Institute of Medicine. Food and Nutrition Board.
  20. ^ Kluger, M. J.; Rothenburg, B. A. (1979). "Fever and reduced iron: Their interaction as a host defense response to bacterial infection". Science 203 (4378): 374–376. doi:10.1126/science.760197. PMID 760197.  edit
  21. ^ a b Nesse, R. M.; Williams, G. C. Why We Get Sick: The New Science of Darwinian Medicine. New York. page 30 ISBN 0-679-74674-9.
  22. ^ T. William Hutchens, Bo Lönnerdal; Lactoferrin: Interactions and Biological Functions (1997). page 379 on Google Books
  23. ^ Nesse, R. M.; Williams, G. C. Why We Get Sick: The New Science of Darwinian Medicine. New York. page 29 ISBN 0-679-74674-9.
  24. ^ Weinberg, E. D. (1984). "Iron withholding: A defense against infection and neoplasia". Physiological reviews 64 (1): 65–102. PMID 6420813.  edit

Further reading[edit]

External links[edit]