Diet as a Modulator of Gut Microbiota May Reduce Alzheimer’s Disease Risk

The aging process, along with an inadequate diet and an inflammatory gut response resulting from dysbiosis, contributes to the pathogenesis of Alzheimer's disease (AD). Modifying the composition of the gut microbiota through appropriate pre/probiotic-rich diets may act as a preventive option for AD. The variety of functions performed by the gut microbiota makes this ecosystem one of the most important systems in the human body. The Mediterranean diet (MedDiet), the Dietary Approaches to Stop Hypertension (DASH), the Mediterranean-DASH Intervention for Neurodegenerative Delay diet (MIND), and the modified ketogenic-Mediterranean diet (MKD) positively affect the intestinal microflora and may reduce the risk of dementia. A ketogenic diet has a neuroprotective effect and improves cognitive function but leads to a significant decrease in the abundance and diversity of bacterial species in favor of harmful bacteria. A Western-style diet (Western diet, WD) rich in processed products, red meat, simple sugars, and saturated fatty acids has a negative impact on gut microbiota function, increasing the risk of AD. Our review supports the hypothesis that factors like a proper diet and a healthy gut microbiota have a positive impact on the prevention of neurodegenerative diseases, including AD. A thorough understanding of the role the microbiota plays in the proper functioning of the nervous system can aid in the prevention of AD by developing new dietary strategies and dietary lifestyles.