Research has shown that a mediteranean diet can is helpful for people with Alzheimers. The study followed people with the disease for four years. Those that ate a diet similar to the mediteranean diet had a far slower mental decline.
A mediteranean diet is high in fruits, vegetables and fibre.
I know that the Mediterranean diet also includes lots of olive oil (instead of cooking with animal fats), fish, herbs and red wine, too. Maybe because it helps with cholesterol it also helps with Alzheimer's! I am no doctor, but it stands to reason that if your circulation is good, the rest of your body will be healthier.