What is the best diet for a person with Alzheimer's?

My goals for mom's diet are to keep her hydrated and prevent UTIs and constipation. Mom eats mainly soft foods such as oatmeal, applesauce, bananas, yogurt, mashed potatoes, soup, canned peaches, and similar things that are easy to chew and swallow. Hospice recommends a few prunes(four a day works for her) to prevent constipation. She drinks a few ounces at a time of coffee, water, juice, seven up, and ensure. This diet is very easy to do. I just have to really make sure to keep her hydrated. She weighs just over 100 lbs. now. She has a good appetite and eats a good breakfast, then smaller meals/snacks throughout the day.

The best diet for a person with AD is anything their heart desires. Life has already dealt out a cruel enough blow with such a diagnosis, no diet is going to alter that diagnosis in one way or another, so let the person at least be happy eating whatever they like without further restricting their already severely limited lifestyle.

When my mom was in MC she was offered 2 choices, but rather than picking from a menu, she chose from 2 plates in front of her. If you are doing the cooking and dont mind leftovers, this may be an option.

A diet is not going to reverse the disease because it has nothing to do with diet. ALZ is a neurological disorder. The one thing I would check out, does he take Cholesterol medication. If yes, as the doctor if it can be discontinued. The Statins in the meds causes cognitively problems. It can be one of the causes of Dementia. Taking the person off of Statins will not stop the disease nut it may make cognitivity better.

My Husband ate all the same things he ate before his diagnosis.
Things did change as he declined and could not eat certain things.
Times of day for the main meal changed. As he slept more I would give him a main meal in the morning as he was more alert and able to eat better.
Meals went from a "normal" meal to minced then to pureed. Liquids went from a regular liquid to nectar thick to honey thick then to pudding thick.
And I also added in additional high fiber foods when necessary. (sometimes as a person becomes less mobile constipation becomes a problem)

It differs from person to person depending on allergies, medical conditions, etc... Can the person still chew? Do they have allergies?

There is no single best answer other than what works best for the person and it will take trial and error to figure it out.