In an article titled: “Stay Healthy to Prevent Dementia”, US News noted:
If diabetes, and obesity are risks of dementia, it would naturally follow that what we eat should be considered. Four recently published studies, found that diet was also a key factor in fending off the risk of dementia. So-called Mediterranean-style diets – stressing fresh fruits and vegetables, fish and olive oil as opposed to saturated fat – had great benefits for brain and heart health. One study even found that people who make only a halfhearted attempt to follow a Mediterranean diet still reduced their risk of brain decline between 18 to 24 percent.
The article also states that exercise and good sleep are also key to reducing the risk of dementia. Read the article at US News: https://www.usnews.com/opinion/policy-dose/articles/2017-08-22/live-healthy-now-to-reduce-your-risk-of-dementia-later