Kynurenic Acid, a Small Foodborne Molecule with the Potential to Affect Human Health

Kynurenic acid (KYNA) is one of the metabolites of tryptophan (Trp), which can be supplied by endogenous synthesis or diet and involves various aspects of nutrition and metabolism. KYNA has been proven to be an antagonist of α7-nicotinic acetylcholine and NMDA receptors, which can regulate the neurotransmission of cholinergic and glutaminergic acid, so KYNA is mainly associated with neurodegenerative diseases. Other metabolites in the Trp and kynurenine metabolic pathways, such as 3-hydroxy-l-kynurenine (3-HK), 5-hydroxytryptophan (5-HT), and quinolinic acid (QA), are also involved in immune regulation and have pro-stimulatory or anti-excitatory toxicity. KYNA is present in both the human body and the daily diet, so it has the potential as a new dietary supplement. It may be of great significance in treating psychiatric disorders.