Editing Iron deficiency (section)

==Bioavailability==
Iron is needed for [[bacterial growth]] making its [[bioavailability]] an important factor in controlling [[infection]].<ref>{{cite journal | vauthors = Kluger MJ, Rothenburg BA | title = Fever and reduced iron: their interaction as a host defense response to bacterial infection | journal = Science | volume = 203 | issue = 4378 | pages = 374–6 | date = January 1979 | pmid = 760197 | doi = 10.1126/science.760197 | bibcode = 1979Sci...203..374K }}</ref> [[Blood plasma]] as a result carries iron tightly bound to [[transferrin]], which is taken up by cells by endocytosing transferrin, thus preventing its access to bacteria.<ref name="Nesse_1996">{{cite book | vauthors = Nesse RM, Williams GC | title = Why We Get Sick: The New Science of Darwinian Medicine |date=1996 |location=New York |edition=First | publisher = Vintage Books | isbn = 978-0-679-74674-4}}</ref>{{rp|30}} Between 15 and 20 percent of the protein content in [[human milk]] consists of [[lactoferrin]]<ref>{{cite book | vauthors = Lien EL | chapter = Modification of Infant Formula: The Case ofLactoferrin| chapter-url = https://link.springer.com/content/pdf/10.1007%2F978-1-4612-3956-7_24.pdf | veditors = Hutchens TW, Lönnerdal B | title = Lactoferrin: Interactions and Biological Functions | series = Experimental Biology and Medicine| url =  | page = 379 |date=1997 |publisher=Humana Press |location=Totowa, NJ | doi = 10.1007/978-1-4612-3956-7_24|isbn=978-1-4612-3956-7}}</ref> that binds iron. As a comparison, in cow's milk, this is only 2 percent. As a result, [[Breastfeeding|breast-fed]] babies have fewer infections.<ref name= "Nesse_1996" /> Lactoferrin is also concentrated in tears, saliva, and wounds to bind iron to limit bacterial growth. [[Egg white]] contains 12% [[conalbumin]] to withhold it from bacteria that get through the eggshell (for this reason, before antibiotics, egg white was used to treat infections).<ref name= "Nesse_1996" />{{rp|29}}

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 [[anemia of chronic disease|anemia of chronic inflammation]].  The underlying inflammation can be caused by [[fever]],<ref>{{cite journal | vauthors = Weinberg ED | title = Iron withholding: a defense against infection and neoplasia | journal = Physiological Reviews | volume = 64 | issue = 1 | pages = 65–102 | date = January 1984 | pmid = 6420813 | doi = 10.1152/physrev.1984.64.1.65 }}</ref> [[inflammatory bowel disease]], infections, [[Heart failure|chronic heart failure]] (CHF), carcinomas, or following surgery.

Reflecting this link between iron bioavailability and bacterial growth, taking oral [[iron supplement]]s over 200&nbsp;mg/day causes a relative overabundance of iron that can alter the types of bacteria 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 protect against acute infection, especially against organisms that reside within hepatocytes and macrophages, such as [[malaria]] and [[tuberculosis]]. This is mainly beneficial in regions with a high prevalence of these diseases and where standard treatment is unavailable.{{citation needed|date=November 2021}}