The article explores the influence of gut-brain axis modulation through prebiotics, probiotics, and symbiotics on cognitive health. It highlights the bidirectional communication between the gut and brain, emphasizing the role of a well-balanced gut microbiota in reducing inflammation and supporting cognitive functions such as attention, perception, and memory. The review includes 23 studies involving 837 healthy individuals, 539 patients with mild cognitive impairment (MCI), and 299 patients with Alzheimer's disease (AD). Key findings include: 1. **Healthy Individuals**: Probiotic, prebiotic, and symbiotic supplementation improved cognitive performance in healthy older individuals, particularly in memory, attention, and visuospatial/constructional abilities. However, one study found no significant improvement in physically active older individuals. 2. **MCI Patients**: Six RCTs showed significant improvements in cognitive functions, including MMSE and ADAS-Jcog scores, in both male and female MCI patients. Probiotics like Lactobacillus and Bifidobacterium, along with prebiotics, were effective in slowing brain atrophy and improving cognitive functions. 3. **AD Patients**: Four studies, including three RCTs and one clinical study, demonstrated significant improvements in cognitive functions, particularly memory and attention, in AD patients. Probiotic interventions, such as kefir and fermented dairy beverages, showed positive effects on MMSE scores and other cognitive measures. The review concludes that probiotics, prebiotics, and symbiotics can improve cognitive performance in healthy individuals and those with cognitive disorders, even after short-term intake. However, further long-term clinical studies are needed to confirm these findings and understand the neuroprotective effects of these dietary supplements. The article also discusses the limitations of the studies, including small sample sizes and the need for more precise dosage regimens. Overall, the review underscores the importance of probiotics in promoting cognitive health and the need for future research to explore the long-term benefits and specific mechanisms of these dietary supplements.The article explores the influence of gut-brain axis modulation through prebiotics, probiotics, and symbiotics on cognitive health. It highlights the bidirectional communication between the gut and brain, emphasizing the role of a well-balanced gut microbiota in reducing inflammation and supporting cognitive functions such as attention, perception, and memory. The review includes 23 studies involving 837 healthy individuals, 539 patients with mild cognitive impairment (MCI), and 299 patients with Alzheimer's disease (AD). Key findings include: 1. **Healthy Individuals**: Probiotic, prebiotic, and symbiotic supplementation improved cognitive performance in healthy older individuals, particularly in memory, attention, and visuospatial/constructional abilities. However, one study found no significant improvement in physically active older individuals. 2. **MCI Patients**: Six RCTs showed significant improvements in cognitive functions, including MMSE and ADAS-Jcog scores, in both male and female MCI patients. Probiotics like Lactobacillus and Bifidobacterium, along with prebiotics, were effective in slowing brain atrophy and improving cognitive functions. 3. **AD Patients**: Four studies, including three RCTs and one clinical study, demonstrated significant improvements in cognitive functions, particularly memory and attention, in AD patients. Probiotic interventions, such as kefir and fermented dairy beverages, showed positive effects on MMSE scores and other cognitive measures. The review concludes that probiotics, prebiotics, and symbiotics can improve cognitive performance in healthy individuals and those with cognitive disorders, even after short-term intake. However, further long-term clinical studies are needed to confirm these findings and understand the neuroprotective effects of these dietary supplements. The article also discusses the limitations of the studies, including small sample sizes and the need for more precise dosage regimens. Overall, the review underscores the importance of probiotics in promoting cognitive health and the need for future research to explore the long-term benefits and specific mechanisms of these dietary supplements.