Iron: Actions

2010

Iron plays a central role in many biochemical processes in the body.

OXYGEN TRANSPORT AND STORAGE

The key function of iron is to facilitate oxygen transport by haemoglobin, the oxygen-carrying pigment of erythrocytes. It is also involved in oxygen storage by myoglobin, an iron-containing protein that transports and stores oxygen within muscle and releases it to meet increased metabolic demands during muscle contraction.

IMMUNITY

Iron is vital for the proliferation of all cells including those of the immune system. Iron deficiency causes several defects in both humoral and cellular immunity, including a reduction in peripheral T cells secondary to atrophy of the thymus and inhibition of thymocyte proliferation and a reduction in IL-2 production. Reduced IL-2 production may partly explain the increased susceptibility to infections and cancer in patients with iron deficiency anaemia. Supplementation of ferrous sulfate (60 mg Fe) once daily for 8 weeks has been shown to reduce the incidence and duration of upper-respiratory tract infections in children.

However, there is also preliminary evidence that iron may be implicated in the pathogenesis of auto-immune disorders, including SLE, scleroderma, type 1 diabetes, Goodpasture syndrome, multiple sclerosis and RA. Current evidence suggests that moderately elevated iron stores may be associated with an overall increased risk for cancer, especially colorectal cancer. Additionally, it has been proposed that iron may increase HIV replication and the rate of progression of HIV infection, although doses of 60 mg of elemental iron twice weekly for 4 months did not appear to affect HIV-1 viral load in clinical studies. Although maintaining adequate iron status may be important for immunity, the benefits of routine supplementation in the absence of deficiency cannot be justified.

ENZYME SYSTEMS

Both haem and non-haem iron are a part of many enzymes that are involved in:

• cellular respiration

amino acid metabolism (e.g. carnitine)

• detoxification (as part of cytochrome P450 enzymes in the liver)

• protection against free radical damage

• synthesis of nutrients such as vitamin A

• synthesis of hormones and neurotransmitters (serotonin and noradrenaline)

• synthesis of collagen and elastin.