Abstract: This comprehensive review explores the intricate relationship between nutrition, the gut microbiome, steroid hormones, and Parkinson’s disease within the context of the gut-brain axis. The gut-brain axis plays a pivotal role in neurodegenerative diseases like Parkinson’s disease, encompassing diverse components such as the gut microbiota, immune system, metabolism, and neural pathways. The gut microbiome, profoundly influenced by dietary factors, emerges as a key player. Nutrition during the first 1000 days of life shapes the gut microbiota composition, influencing immune responses and impacting both child development and adult health. High-fat, high-sugar diets can disrupt this delicate balance, contributing to inflammation and immune dysfunction. Exploring nutritional strategies, the Mediterranean diet’s anti-inflammatory and antioxidant properties show promise in reducing Parkinson’s disease risk. Microbiome-targeted dietary approaches and the ketogenic diet hold the potential in improving brain disorders. Beyond nutrition, emerging research uncovers potential interactions between steroid hormones, nutrition, and Parkinson’s disease. Progesterone, with its anti-inflammatory properties and presence in the nervous system, offers a novel option for Parkinson’s disease therapy. Its ability to enhance neuroprotection within the enteric nervous system presents exciting prospects. The review addresses the hypothesis that α-synuclein aggregates originate from the gut and may enter the brain via the vagus nerve. Gastrointestinal symptoms preceding motor symptoms support this hypothesis. Dysfunctional gut-brain signaling during gut dysbiosis contributes to inflammation and neurotransmitter imbalances, emphasizing the potential of microbiota-based interventions. In summary, this review uncovers the complex web of interactions between nutrition, the gut microbiome, steroid hormones, and Parkinson’s disease within the gut-brain axis framework. Understanding these connections not only offers novel therapeutic insights but also illuminates the origins of neurodegenerative diseases such as Parkinson’s disease.

Key words: diet, gut-brain axis, microbiome, neurodegenerative diseases, nutrition, Parkinson’s disease, progesterone, steroid hormones