An extensive article that is behind the New Scientist paywall so I am including my favorite three paragraphs as per the fair use doctrine...
Food for thought: Eat your way to dementia
If McNay and de la Monte are correct, a similar process may lead to Alzheimer's. They think that constantly high levels of insulin, triggered by the fat and sugar content of the western diet, might begin to overwhelm the brain, which can't constantly be on high alert. Either alongside the other changes associated with type 2 diabetes, or separately, the brain may then begin to turn down its insulin signalling, impairing your ability to think and form memories before leading to permanent neural damage. "I believe it starts with insulin resistance," says de la Monte. "If you can avoid brain diabetes you'll be fine. But once it gets going you are going to need to attack on multiple fronts."It's a really good summary and there's lots of great ideas on how insulin could be causing dementia. (my guess) Ordinarily I would be dancing and showering a cover article (!) like this with praise.
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Of course, animal studies can only tell you so much about a human disease, but an almost Frankensteinian demonstration confirms that the brains of people with Alzheimer's are insulin-resistant. Using brains from cadavers, Steven Arnold at the University of Pennsylvania bathed various tissue samples in insulin to see how they would react. Tissue from people who had not had Alzheimer's seemed to spring back to life, triggering a cascade of chemical reactions suggestive of synaptic activity. In contrast, the neurons of those who had had Alzheimer's barely reacted at all (Journal of Clinical Investigations, vol 122, p 1316). "The insulin signalling is paralysed," says Arnold.
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It's not yet fully understood exactly why disrupted insulin signalling would lead to the other kinds of brain damage associated with Alzheimer's, such as the build up of plaques, though the emerging research suggests many, possibly interlinked, mechanisms. One line of evidence, for instance, has shown that insulin and beta amyloid are both broken down by the same protein-chomping enzyme. Under normal circumstances that enzyme can successfully deal with both, but if too much insulin is washing around, the enzyme gets overwhelmed by the hormone, and the beta amyloid gets neglected. Instead of being broken down, it accumulates, perhaps building into the toxic plaques that kill brain cells.
But the author repeatedly asserts that fatty foods trigger insulin production and even though that idea is now "common knowledge" - it is just not true. Carbohydrates do. Sugar. Sugar. Sugar.
One would expect in an article subtitled "What you eat may be killing your brain" - there would be a minimal attempt to get the facts straight about the effects of food.
The reason we are all crazy sick is a century of sloppy assumptions just like that.
