This last condition is not new, although it has played a critical role in recent years in the knowledge of pathophysiology because high intestinal permeability is intimately linked to increased low-grade inflammation, metabolic syndrome, autoimmune disorders, neurological alterations, malabsorption, nutritional deficiencies [62,65,66], alterations in diamine oxidase enzyme (DAO) with loss of skeletal muscle strength [67], and increased perceived pain, which has a direct effect on the intestinal microbiota [68]. Here, DAO is linked to metabolic syndrome.