Iron, a common mineral (and, paradoxically, a common mineral deficiency in humans) is important to the brain and vital for normal brain development and human behavior. It is a key cofactor in the making of neurotransmitters, chemicals in the brain that affect neuron signaling, including serotonin, norepinephrine, and especially dopamine. Iron is also necessary for the enzyme monoamine oxidase to break down these neurotransmitters