This is quite a controversial one. Some people swear by it, but there has been no solid scientific evidence to support its effectiveness in treating mild cognitive impairment (MCI) or Alzheimer’s disease. https://www.alzheimers.org.uk/about-dementia/treatments/alternative-therapies/coconut-oil-and-dementia
One of most well-known proponents of using coconut oil to treat Alzheimer’s disease is Dr. Newport. Around 2008, her husband developed Alzheimer’s disease. She started treating him with a high dose of coconut oil and he showed significant improvement. She has since been promoting it and has a website where she describes details of the treatment. http://www.alzheimersweekly.com/2016/10/how-much-coconut-oil-helps-alzheimers.html
I do have some experience using coconut oil with my wife, who died from Alzheimer’s disease not so long ago. I was her primary caregiver throughout her illness, and I tried feeding her a diet with that included a large amount of coconut oil to see if this would help with her symptoms. Unfortunately, after a few months I did not observe any improvement whatsoever, so I stopped administering it.
Based on this experience, I am not following the coconut oil regimen myself.
However, Dr. Newport’s husband did get better using coconut oil, so it seems like it might work for some people. My guess is that it depends on the type of underlying conditions, so in some cases it may help and in other cases it may not. Therefore, it could be worthwhile to try it. However, if you do decide to give it a shot, you will need to be careful because coconut oil is a saturated oil, so it could cause other health problems. For this reason, I recommend that you consult your doctor before trying it yourself.