The iron found in the Modern Multi is an amino acid chelate, which means that the iron molecule is attached to an amino acid in order to support optimal absorption by the body. Iron is a major component of hemoglobin, a protein in red blood cells that carries oxygen to all parts of the body. Without enough iron, there aren't enough red blood cells to transport oxygen which can lead to fatigue and lightheadedness. Studies have shown that taking iron bisglycinate (the form found in the Modern Multi) rather than ferrous sulfate (the form of iron traditionally found in multivitamins) is associated with fewer digestive side effects.†