Why the MIND diet excludes cheese, butter, and margarine -- now we may know

In the longitudinal studies the late Dr. Martha Clare Morris conducted that led to the development of the MIND diet, Dr. Morris found an association between consumption of red meat, butter, stick margarine, and cheese with the development of Alzheimer's disease.  So these are excluded from the MIND diet, even if they might be more tolerated in the Mediterranean diet.  When I speak to a group about diet, and I say that avoiding saturated fats helps insulate you from Alzheimer's disease, I hear groans.  Especially when I mention the cheese.

Longitudinal studies look at associations of behaviors and possible consequences over time, without necessarily explaining the reason for the associations.  So correlation isn't causation, and maybe there's some weird reason for the association that, if understood, would allow us to go back to cheese.  Unfortunately...

Saturated fats, cholesterol, and high-fat diets got a lot of bad press in the 1980s and 90s as being strongly correlated with heart disease.  But it turned out that the evidence for these associations was weak, and the government and health authorities backed off on strong recommendations that food high in saturated fats and cholesterol be avoided.  For example, it seemed like eggs were just poison, because they have so much cholesterol in the yolks.  But later research failed to find the strong link between egg consumption and the actual heart disease postulated by the cholesterol-heart disease hypothesis.  So they told us to go back to eating eggs.

So while the evidence of an association between a diet high in saturated fats and heart disease began to weaken, the association with Alzheimer's disease actually strengthened.  But what was the basis for the association?  I've been wondering this for a while.  And maybe we now know.

I came across this article on the science news web site, PsyPost.  It cites research from the journal, Nutrients, which claims to have found evidence that could explain the association between saturated dietary fats (cheese, butter, etc.) and Alzheimer's disease.  But it's kind of complicated, so you may just want to know that they think they're better able to explain the relationship between consumption of saturated fats and the development of obesity, type 2 diabetes, and Alzheimer's disease.  (Note that this particular study does not connect heart disease with a diet with saturated fats.)

Going a little deeper, the study examined the role of microRNAs (miRNA) in the "expression of genes."  Which means how proteins are generated when genes in DNA are read by messenger RNA (mRNA).  The miRNA (which have only been recently discovered) are supposed to regulate the production of proteins by exercising control over the mRNA that's making the proteins.  There are many different types of miRNA influencing the production of many different proteins.  Many of the miRNA live in parts of the brain like the hippocampus -- ground-zero for Alzheimer's disease.  Some can influence the development of insulin resistance in the brain.  As we explained in Beating the Dementia Monster, as insulin resistance advances we call it type 2 diabetes and it is strongly associated with Alzheimer's disease.

With that background, the researchers studied the diets of mice (again...) along with changes in their memories and other abilities.  The researchers also examined the mouse brains in autopsy.  They controlled the mouse diets so that the mice consumed known amounts of saturated fats.  The researchers found that a diet high in saturated fat seemed to disrupt the miRNA in its task of allowing proper generation of proteins and the work of insulin in signaling cells to consume glucose.  An important part of both type 2 diabetes and Alzheimer's disease is the failure of cells to properly take up and metabolize glucose.  And so they call Alzheimer's disease type 3 diabetes.  (We discussed all of this in Beating the Dementia Monster.)

It appears to me that this is a very different pathway to type 2 diabetes than the one we discussed in Beating the Dementia Monster.  The better known pathway is excessive consumption of carbohydrates generates a steady output of insulin that overwhelms the cells.  The insulin is supposed to signal the cells to take up glucose, but it hits a point where the overwhelmed cells stop taking up glucose.  Then glucose levels in the blood get excessively high and begin damaging organs.

This was all fascinating to me, but I'm not sure how many of you are still here.  The bottom line?  Staying away from red meat, butter, stick margarine, and cheese remains part of a diet for those of us avoiding or fighting Alzheimer's disease.