Hb is the main protein that delivers oxygen to tissues throughout the body, and the brain accounts for 20% of the body’s oxygen consumption; low hemoglobin leads to cerebral hypoxia, which in turn decreases brain tissue metabolism and neuronal activity, further leading to mitochondrial dysfunction, oxidative stress, and inflammatory responses and ultimately cognitive dysfunction; low Hb-associated iron deficiencies in the brain may also affect neurotransmitter metabolism and function (44, 45). This evidence concerns the gene GSTM1 and nutritional disorder.