The keto diet has shown to improve cognitive decline because it provides an alt fuel to glucose. Alzheimer's is also called Type 3 diabetes, because victims cannot process glucose for energy (including brain energ) normally. Keto is a high fat diet. This advice directly contradicts the ubiquitous "eat grains and veggies and fruits" advice and what most people interpret as a Mediterranean diet. As you point out, Alzheimer's isn't a genetic condition. There is massive evidence it is a metabolic disease, like diabetes and probably cancer.