The Mediterranean diet appears to delay signs of Alzheimer's disease.

Some preliminary research has shown that regular consumption of olive oil may help prevent overall cognitive decline, as well as may keep the neural connections unhindered from plaque build-up.

Sources:

https://content.iospress.com/articles/journal-of-alzheimers-disease/jad110662

https://onlinelibrary.wiley.com/doi/full/10.1002/acn3.431

https://newsnetwork.mayoclinic.org/discussion/mayo-clinic-minute-the-diet-that-could-improve-your-brains-health/"