Histidine is a unique amino acid that is best known as the precursor to histamine, a natural substance related to a healthy immune response. As such, L-histidine supplements are most often used for their immune-supporting benefits. But it’s also a crucial element in the production of Superoxide Dismutase (SOD), one of your body’s most important (and most prolific) antioxidants. Your body also uses histidine to assimilate iron, as well as to help transport important trace elements throughout your body. Dairy, red meat, poultry and fish are all good natural sources of histidine.