Body’s Protein Aversion May Be Natural Defense Against Toxic Build-Up,new Research Suggests
HAMBURG,Germany – A newly published study from University Hospital Hamburg-Eppendorf (UKE) reveals that the body’s tendency to reject protein-rich foods during recovery from illness or metabolic stress may not be a malfunction,but a crucial protective mechanism against ammonia toxicity. Researchers discovered a gut-to-brain signaling pathway activated by ammonia, triggering nausea and aversion to protein intake - a response perhaps safeguarding the body when liver detoxification capacity is compromised.
The findings, published in Cell on October 10, 2025 (DOI: https://doi.org/10.1016/j.cell.2025.10.005), center around the amino acids glutamine, lysine, and threonine (QKT). Breakdown of these amino acids produces ammonia,normally detoxified by the liver. However, the research team, led by Dr.Nicola Jaschke, found that the recovery process itself can temporarily reduce this detoxification ability. Supplementation with QKT proved toxic in experiments, leading the scientists to hypothesize that protein aversion is a natural response to prevent harmful ammonia accumulation.
The team identified a specific protein in the intestine that is activated by locally formed ammonia. this activation sends signals via ascending nerve fibers to brain regions responsible for triggering nausea and aversion. Interestingly, Dr. Jaschke notes, “The brain areas activated by protein or ammonia partially overlap with those that are stimulated by modern appetite-suppressing medications with the active ingredient semaglutide.”
This discovery opens avenues for targeted dietary interventions to support recovery in critically ill patients, and also individuals with congenital metabolic diseases or cachexia – a metabolic disorder often associated with cancer. Dr. Jaschke and her team at the I. and III. Medical clinic and polyclinic at UKE (Martinistraße 52, 20246 Hamburg; Jaschke@uke.de) are now focused on testing whether dietary strategies can optimize the human recovery process based on these findings.
