Iron Deficiency - Bioavailability and Bacterial Infection

Bioavailability and Bacterial Infection

Iron is needed for bacterial growth making its bioavailability an important factor in controlling infection. Blood plasma as a result carries iron tightly bound to transferrin, and only releases it to cells with appropriate cell markers thus preventing its access to bacteria. Between 15 and 20 percent of the protein content in human milk consists of lactoferrin that binds iron. As a comparison, in cow's milk, this is only 2 percent. As a result, breast fed babies have fewer infections. 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).

To reduce bacterial growth, plasma concentrations of iron are lowered in inflammatory states in the body, such as those caused by fever, and following surgery after open wounds where it acts as a protection against infection. Reflecting this link between iron bioavailability and bacterial growth, the taking of iron supplements can increase the risk of infection. A moderate iron deficiency, in contrast, can provide protection against acute infection. This is due to the release of hepcidin from the liver.