The role of iron in immunonutrition has been widely discussed and confirmed by many studies [133]. Iron is required for a number of different cellular functions and there is a constant balance between iron uptake, transport, storage, and utilization required to maintain iron homeostasis [134, 135]. As the body lacks a defined mechanism for the active excretion of iron, iron balance is mainly regulated at the point of absorption. Iron deficiency induces thymus atrophy and has multiple effects on immune function in human subjects [133, 136].