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Does Sugar Raise Alzheimer's Risk?
Disturbing findings reveal how sugar makes brains vulnerable to dementia; Low-carb/high-fat diets look promising

03/16/2017

Scientists at Brown University Medical School posed a radical idea back in 2005.

They’d noticed a striking similarity between diabetes and Alzheimer’s disease — namely, an inability to properly regulate insulin and blood sugar.

By 2008, the Brown University group had concluded that the then-available research supported their idea.

As they wrote, “We conclude that the term “type 3 diabetes” accurately reflects the fact that AD [Alzheimer's disease] represents a form of diabetes that selectively involves the brain …”.

Since then, the evidence that Alzheimer’s is triggered or worsened by excessive sugar intake — an unhealthful hallmark of the standard American diet — has grown considerably.

Now, new research from the Netherlands adds another good reason to avoid sugar — to help avoid Alzheimer’s and ease its impact.

What do diabetes and Alzheimer’s have in common?
Even mild elevation of blood sugar is linked to a higher risk for dementia.

Why would that be?

Insulin is the hormone needed for your cells to absorb sugar (glucose) from the blood. Cells then either store that sugar for future use, or use it to produce immediate energy.

When your cells don’t absorb sugar in response to a normal amount of insulin, this condition is called insulin resistance, and it’s the precursor to full-blown diabetes.

Because your brain depends on blood sugar (glucose) as its primary fuel, insulin resistance threatens the survival of brain cells (neurons).

Insulin also influences the release and reuptake of neurotransmitters, and can thereby affect learning and memory.

So, if your brain cells can’t absorb sugar, this will lead to problems, including dementia.

Even worse, insulin-resistant brain cells lose their ability to detoxify the amyloid-beta proteins associated with Alzheimer’s — thereby causing a deterioration in thinking and memory.

These facts explain the growing evidence that improper regulation of insulin promotes — or even triggers — Alzheimer’s.

For example, diabetics are about twice as likely to develop Alzheimer’s, while brain scans show that greater insulin resistance results in less glucose (brain fuel) in brain areas typically affected by Alzheimer's.

And as Alzheimer’s disease progresses, there's a simultaneous drop in the amount of blood sugar used in key regions of the brain.

Finally, blood glucose and its break-down products can damage proteins in cells, via a reaction called glycation, in which proteins bind to sugars.

Glycation also yields chemicals called “advanced glycation end-products”, which generate chronic inflammation in the body.

The acronym for these chemicals — AGEs — is sickeningly appropriate, because chronic inflammation accelerates aging of cells and tissues.

We’ve reported on past research linking excessive dietary sugars to dementia: See Carbs Fog Aging Brains and Blood-Starved Brains Shown Prone to Alzheimer’s.

And early research suggests that seafood-source omega-3 fatty acids (DHA and EPA) may blunt sugar-related brain damage: See Fructose Harms Brain Genes; Omega-3s Undo the Damage and Sugary Brain Damage Blunted by Omega-3s.

Now, new findings show there’s a “tipping point” beyond which elevated blood sugar levels substantially raise the risk for Alzheimer’s.

New finding: Excess blood sugar disables a brain-protective enzyme
British scientists have discovered that excess blood sugar (glucose) has another bad effect.

They found that excess blood sugar damages an enzyme the body uses to reduce the inflammation known to occur in the early stages of Alzheimer’s.

The new findings come from scientists at Britain's University of Bath and King’s College London.

They examined brain samples from people with and without Alzheimer’s, and discovered that — in the early stages of Alzheimer’s — glycation damages an enzyme called MIF that affects inflammation and insulin alike.

Conversely, when the fatty tissue in obese people releases MIF, the enzyme appears to promote metabolic and inflammatory processes that drive obesity-related damage to health.

However, as Dutch researchers recently reported, “Although many of the findings support a pro-inflammatory role of MIF in disease development, recent reports also provide indications that MIF may exert protective effects under certain conditions.”

The new British findings support that statement, because they show that MIF exerts protective effects against the development of Alzheimer’s disease.

Special brain cells called glia — which support, insulate and feed the neurons involved in thinking and memory — use the MIF enzyme to reduce the build-up of abnormal proteins in the brain that’s a hallmark of Alzheimer’s disease.

The British researchers found that the inhibition and reduction of MIF activity caused by glycation could be the tipping point in disease progression.

And they discovered that as Alzheimer’s progresses, damaging glycation of these protective MIF enzymes increases.

According to study co-author Jean van den Elsen, “Normally, MIF would be part of the immune response to the build-up of abnormal proteins in the brain, and we think that — because sugar damage reduces some MIF functions and completely inhibits others — that this could be a tipping point that allows Alzheimer’s to develop.”

His colleague, Dr. Rob Williams, addressed the possible medical uses of their discovery: “Knowing this will be vital to developing a chronology of how Alzheimer’s progresses and we hope will help us identify those at risk of Alzheimer’s and lead to new treatments or ways to prevent the disease.”

Ketones: Healthier brain fuels from low-carb/high-fat diets?
Paleo- and Atkins-style diets strictly limit intake of sugars and starchy carbs.

Instead, they get many more of their calories from fats and protein: a pattern that allegedly hews closer to the diets eaten thoughout most of human history, except the past 10,000 to 15,000 years.

In fact, the diets of Neanderthals and prehistoric humans remain unclear.

Recent research suggests that they varied widely — from meat-focused to plant-focused — based on a particular group's environment.

And this evidence shows that some Paleolithic diets included very substantial amounts of wild legumes, grasses, and grains ... including cooked grains.

Last, it's increasingly clear that humans can and have adapted to changes in diet over a few thousand years, and that many people thrive on diets relatively high in Paleo-diet "no-nos" like grains and dairy.

Regardless of what certain prehistoric ancestors ate (or didn't), low-carb, high-fat diets may bring some big brain benefits, thanks to chemicals called ketones.

The brain normally runs on glucose stored in the liver as glycogen, but a very-low-carb diet depletes the liver's glycogen supply, prompting the organ to produce alternative, fat-derived fuel in the form of ketones.

This explains why Paleo and Atkins-style diets are sometimes called "ketogenic".

Preliminary clinical evidence suggests that ketogenic diets amply fuel the brain while boosting its performance, with the degree of cognitive enhancement tied to a person's blood ketone levels.

Emerging evidence about the brain damage caused by diets high in sugars and refined carbs suggests that shifting your brain fuel from glucose toward ketones may reduce your risk of Alzheimer's and other forms of dementia, delay their onset, and/or ease their symptoms.

If you decide to try a ketogenic diet, be aware that coconut oil features fats called MCTs, which the body readily converts into brain-fueling ketones.

What should you do?
Dr. Omar Kassaar, a co-author of the new Dutch study, urged people to act on its findings.

As he said, “Excess sugar is well known to be bad for us when it comes to diabetes and obesity, but this potential link with Alzheimer’s disease is yet another reason that we should be controlling our sugar intake in our diets.”

We’d add that it’s smart to avoid refined, sugary carbs — such as white-flour baked goods, white rice, potatoes (except their nutritious skins), and other starchy, nutrient-poor foods.

But for most people, it’s clearly healthful to enjoy modest portions of genuinely whole-grain foods — quinoa, buckwheat, wheat berries, brown or black rice, and coarse whole-grain breads, especially sourdough varieties.

It’s also wise get most of your carbs from colorful vegetables and beans, rich in healthy fibers and antioxidants.

Last, but far from least, low-carb/high-fat diets — such as Paleo- or Atkins-style plans — probably help protect against dementia, and may boost brain performance.

But don't rely on cheap vegetable oils — specifically, corn, soy, sunflower, and safflower — which are high in omega-6 fats. 

That's because the average American's excessive intake of omega-6 fats from harms brain and overall health. (See our Omega Balance page and the Omega-3 / Omega-6 Balance section of our news archive.)

Instead, it makes sense to favor omega-3 fats from fish, monounsaturated fats (avocados, extra virgin olive oil, macadamia nut oil, canola oil), MCTs from coconut oil, and saturated fats.


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