I realize that a LC/HF diet can help prevent alzheimer's - the reason my mother always ate a very low fat high carb diet is that she always despised the taste/texture of "grease" of any kind. She would reduce the amount of oil/butter/margarine/Crisco (She's 90 now -margarine and Crisco were a big part of her era) in recipes, because they were too greasy for her tastes. She would skim every smidgen of grease possible off broth from beef or chicken before using the broth to make gravy. She made at least one cake weekly (usually ate it for breakfast), and even though she'd frost it, she used as little frosting as possible, because of the amount of grease in the frosting. (She'd always make a sheet cake, using only half a can or less of frosting for the cake - sometimes she'd spread the frosting so thin that a can of frosting would cover 3 cakes) Eventually, she developed what she called a breakfast cake, which was just a type of spice cake which had a lot of dried fruits added to it. This was her way of eating long before all the propaganda about fat making you fat - she just always hated any kind of fats in/on her food, and avoided them as much as possible, any way she could.

She also always felt the need for a sugary or starchy "pick me up" at least once or twice during the afternoon, often at least once in the mid-morning too. While she understood at one point that I did not react well to sugars and starches because of my hypoglycemia, she still believed she needed the sugar in her diet, that it wasn't a problem for her, since her blood sugar was considered normal. Even when she was later convinced that she needed to avoid candy and cookies for her sugary pick-me-up, she either ate fruit (apples, bananas, grapes - some of the highest carb fruits), or else sweetened applesauce and graham crackers. She didn't have big snacks, but they were still almost all sugar and starch.

At her age, and with her food preferences (even with her mind going so quickly, she still hates anything she considers to be greasy), I don't think there's really any chance of slowing or reversing her alzheimer's progression through diet. I'm as anti-drug as they come, but if there's a possibility that her condition could be improved some with a drug, then under the circumstances, I think it's worth a try.