Note the standard recommendations for fish or krill oil and Vitamin D which all of us should be taking. Take a look at some of my previous posts for more detailed information, too.
Does following Dr. Amen's advice help someone already with dementia? Perhaps early on but a well-regulated regimen of supplements, physical and mental exercise, and medications is the best approach. While I hope family members can get involved in their parents' care, early intervention is critical to minimize damage and prolong a quality life. Getting mom or dad to admit she or he has a problem is also a challenge. My best advice: do not enable. Do not tell your parent that everything is fine. Do not allow your siblings to enable either. Easier said than done. Trust me.