Health News Digest

November 3, 2008

Does A High-Fat Diet Promote Alzheimer’s Disease?

Brain on fat

By  Michael D. Shaw

We’ve been hearing for years about all the bad things that occur when we stay on a high-fat diet. The long list of maladies includes cardiovascular disease, strokes, diabetes, various forms of cancer, liver disease, sleep problems, inflammatory bowel disease, and kidney conditions. Now, a research group from Quebec’s Université Laval has evidence pointing to a high-fat involvement in Alzheimer’s Disease, as well.

But first, some background…

For several years, it has been hypothesized that Alzheimer’s is a protein misfolding disease, caused by an accumulation of abnormally folded amyloid-beta proteins in the brains of affected individuals. In 2002, it was reported that so-called tau proteins must be present to enable amyloid-beta to induce the degeneration of brain cells that occurs in Alzheimer’s disease. Amyloid-beta is a peptide of 39-43 amino acids that appears to be the main constituent of amyloid plaques in the brains of Alzheimer’s disease patients.

The 2002 work—done at Northwestern University—showed that neurons with normal amounts of tau degenerated in the presence of amyloid-beta, while neurons specially treated to be devoid of tau did not degenerate.

As such, tau and amyloid-beta are used as experimental markers for Alzheimer’s.

The Laval team, led by Frédéric Calon had two groups of mice, one a special transgenic type (a foreign gene is inserted into the animal’s genome) that produce the tau and amyloid beta proteins, and non-transgenic littermates. Cohorts of the transgenic and regular mice were fed either a high-fat (35%) low Omega-3; low-fat (5%) low Omega-3; or control diet. After several months, the research group examined how these diets affected the mice brains.

The amyloid-beta and tau protein concentrations in the high-fat diet mice were respectively 8.7 and 1.5 times higher than the control diet mice. Another finding was that levels of the neurological protein drebrin were reduced in the high-fat diet mice, and this is also a characteristic of Alzheimer’s.

This research was published in the 15 October 2008 edition of the online journal Neurobiology of Aging, in an article entitled “High-fat diet aggravates amyloid-beta and tau pathologies in the 3xTg-AD mouse model.” Study co-author Carl Julien commented, “Metabolic changes induced by such a diet could affect the inflammatory response in the brain.”

Dr. Calon remarked further:

“Our findings lead us to believe that a diet containing more omega-3s and less saturated fat could prevent the development of Alzheimer’s, at the very least among people genetically predisposed to the disease. We cannot state with any certainty that what we have observed among transgenic mice also occurs in humans, but there is no harm in eating less fat and more Omega-3s.”

There are plenty of rodent studies, based on the flimsiest of correlations, which are used to justify expensive and draconian environmental policies. Here, though, is good science looking at proteins occurring in man and mouse, whereby a correlation seems much more compelling. Besides, there are many other good reasons to consume less fat and more Omega-3s.

Just one more example of the old adage “you are what you eat.”