## 3 Results
### What Is the Impact of A1 \(\beta\)-Casein on Neurological and Cognitive Health?
Additionally, the related peptide (D-Pro4)-\(\beta\)-CM-5 has been found to influence the synaptic transmission of acetylcholine in the hippocampus and dopamine in the striatum, possibly through interactions with serotonin and dopamine receptors [46]. Elevated concentrations of casomorphins may exert pathological effects on both opioid and serotonergic signaling. For instance, in vitro studies have demonstrated that \(\beta\)-CM-7 can displace the 5-HT2 receptor ligand \({}^{3}\)H-spiperone in rat frontal cortex membranes, as well as inhibiting serotonin-induced platelet aggregation in human blood samples. These findings support the idea that \(\beta\)-CM-7 may function as a 5-HT2 receptor antagonist. Furthermore, in vivo experiments have shown that \(\beta\)-CM-7 suppresses 5-hydroxytryptophan-induced hyperactivity of the serotonergic system in mice, an effect that was reversed by naloxone--suggesting an interaction between serotonergic and opioid systems [44]. Although most of the current literature explores these mechanisms in relation to autism, the influence of \(\beta\)CM-7 on the serotonergic system may also have broader implications for other neuropsychiatric conditions. These findings underscore the need for further investigation into the neuroactive properties of milk-derived peptides and their potential roles in modulating CNS function beyond developmental disorders. As [PERSON] et al. [63] point out, significantly elevated concentrations of \(\beta\)CM-7 have been found in the blood plasma and urine of patients with schizophrenia, autism, and postpartum psychosis, reinforcing the potential similar involvement in other mental illnesses [47; 70; 71; 72]. This study evaluated the comparative effects of dairy products containing only A2 \(\beta\)-casein versus conventional dairy products on symptoms of psychological distress in women with low mood. Research suggests that A1 \(\beta\)-casein is involved in pathways thought to be important for the etiology of mental disorders, including inflammation, oxidative stress, and gut microbiota [63]. The intestinal and systemic inflammatory response induced by \(\beta\)CM-7 [28; 32; 33], has been proposed as a pathway connecting diet with neurological and psychiatric disorders and depression [22; 47; 63; 73]. The reduction in glutathione (GSH) associated with A1 \(\beta\)-casein consumption can increase the inflammatory, oxidative, and nitrosative stress load [39]. Oxidative stress is implicated in the pathogenesis of several mental disorders, including depression and schizophrenia [73]. [PERSON] (2019) also suggests that reduced cysteine uptake and the resulting decrease in glutathione synthesis due to opioid peptides in milk could have consequences in neurological disorders [22]. The alteration of the gut microbiota due to the increased gastrointestinal transit time induced by \(\beta\)CM-7 could be relevant to mental disorders. The gut-brain axis is a bidirectional communication pathway, and alterations in microbiota composition and function have been linked to depression and other neuropsychiatric disorders [74; 75; 76]. [PERSON] et al. observed lower levels of short-chain fatty acids (SCFAs) with A1 \(\beta\)-casein consumption, which could have implications for colon health and, through the gut-brain axis, potentially for mental health [33]. However, it is important to note that research in this field is complex and not always conclusive. In summary, A1 \(\beta\)-casein and its digestion product, \(\beta\)CM-7, are implicated in the pathogenesis of neurological disorders such as autism and schizophrenia, as well as in psychomotor development. However, further research is needed to confirm these effects and elucidate the underlying mechanisms.