Insulin Resistance Speeds Up Cognitive Decline

insulin resistance and alzheimer disease

Story at-a-glance

  • Mounting research suggests Alzheimer’s disease is intricately connected to insulin resistance; even mild elevation of blood sugar is associated with an elevated risk for dementia
  • A study that followed seniors with heart disease over 20 years found those with the highest levels of insulin resistance had the worst cognitive performance and scored lowest on memory and executive function tests
  • Insulin resistance appears to promote cognitive decline by adversely impacting the blood vessels in your brain, promoting the formation of plaques and hindering memory formation


This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.

By Dr. Mercola

We are facing a tsunami of Alzheimer's disease. It's often said that the underlying causes of Alzheimer's disease are unknown, but there are numerous theories. For example, research suggesting that an infectious component is at play is becoming increasingly difficult to ignore.

In addition to viruses, bacteria and fungi, an infectious protein called TDP-43, which behaves like infectious proteins known as prions — responsible for the brain destruction that occurs in Mad Cow and Chronic Wasting Diseases — has been linked to the disease. Research presented at the 2014 Alzheimer's Association International Conference revealed Alzheimer's patients with TDP-43 were 10 times more likely to have been cognitively impaired at death than those without.1

Due to its similarities with Mad Cow Disease, investigators have raised the possibility that Alzheimer's disease may be linked to eating meat from animals raised in concentrated animal feeding operations (CAFOs).

Mounting research also suggests Alzheimer's disease is intricately connected to insulin resistance; even mild elevation of blood sugar is associated with an elevated risk for dementia.2 Diabetes and heart disease3 are also known to elevate your risk, and both are rooted in insulin resistance.

Even Mild Insulin Resistance Speeds Cognitive Decline

According to Dr. David Perlmutter, a neurologist and author of "Grain Brain" and "Brain Maker," Alzheimer's disease is primarily predicated on lifestyle choices, and anything that promotes insulin resistance, like a processed food diet, will ultimately also raise your risk of Alzheimer's.

There's already plenty of evidence supporting this view, and new research4,5,6 strengthens the link between insulin resistance and dementia even further, particularly among those with existing heart disease. As reported by Reuters:7

"Having reduced sensitivity to insulin may lead to more rapid decline in memory and other mental skills in old age even among people who don't have diabetes, a recent study suggests …

[R]esearchers followed 489 older adults for more than two decades … [P]eople with the highest levels of insulin resistance had the worst cognitive performance and the lowest scores on tests of memory and a mental skill known as executive function.

'There is growing evidence that insulin carries out multiple functions in the brain and thus poor regulation of insulin may contribute to accelerated cognitive decline and potentially to Alzheimer's disease,' said senior study author David Tanne of Tel Aviv University in Israel.

'It is not just people with type 2 diabetes,' Tanne said … 'Even people with mild or moderate insulin resistance who don't have type 2 diabetes are at increased risk over time.'"

Tanne gave the following advice to readers of Diabetes Daily:8 "Exercising, maintaining a balanced and healthy diet, and watching your weight will help you prevent insulin resistance and, as a result, protect your brain as you get older."

Alzheimer's Disease — A Form of Diabetes?

While the exact mechanisms are still unclear, insulin resistance appears to promote cognitive decline by adversely impacting the blood vessels in your brain, promoting the formation of plaques and hindering memory formation, as insulin is involved in your brain's formation of synaptic connections. Researchers have been aware of the link between insulin resistance and Alzheimer's for well over a decade.

In 2005, Alzheimer's was tentatively dubbed type 3 diabetes when researchers realized that, along with your pancreas, your brain also produces insulin and related proteins, and that this brain insulin is necessary for the survival of your brain cells.9 Interestingly, while low insulin levels in your body are associated with improved health, the opposite appears to be true when it comes to brain insulin.

Reduced insulin production in your brain actually contributes to the degeneration of brain cells, and studies have found that people with lower levels of insulin and insulin receptors in their brain often have Alzheimer's disease. According to researchers,10 "These abnormalities do not correspond to Type 1 or Type 2 diabetes, but reflect a different and more complex disease process that originates in the central nervous system."

Interestingly, late last year, researchers at John's Hopkins Department of Biology discovered that nerve growth factor (NGF), a protein found in your nervous system that is involved in the growth of neurons, also triggers insulin release in your pancreas.11

Byproduct From Gut Bacteria Helps Prevent Type 2 Diabetes

In related news, researchers in Finland recently found that having higher levels of indolepropionic acid, a byproduct of gut bacteria, helps protect against type 2 diabetes. Medical News Today reports:12

"… [F]actors such as genes, lifestyle and diet can influence the risk of developing type 2 diabetes. However, what is less clear is what happens at the molecular level to link these factors to the disease.

The new study uses metabolomics, a relatively new technology that allows scientists to quickly assess the metabolite profiles of people. Metabolites are molecules that cells in the body — including gut bacteria — produce as byproducts of their activity.

Using a particular tool called "nontargeted metabolomics analysis," the researchers assessed the metabolite profiles of 200 participants … who had impaired glucose tolerance and were overweight … One group developed type 2 diabetes within five years, and the other group did not develop type 2 diabetes during the 15 years of follow-up.

When the researchers compared the metabolite profiles of the two groups, they found … differences in levels of indolepropionic acid and certain lipid metabolites … [H]aving high blood levels of indolepropionic acid, a byproduct of gut bacteria, appeared to protect against developing type 2 diabetes.

Also, a diet rich in fiber and whole grain foods appears to increase levels of indolepropionic acid, which in turn raises the amount of insulin produced by the beta cells in the pancreas …"

Previous research13 has shown that people with the highest intake of fiber (more than 26 grams a day) had an 18 percent lower risk of developing type 2 diabetes than those with the lowest intake (less than 19 grams a day).

Inulin, a prebiotic fiber found in onions, leeks, and garlic (among many other foods), has also shown particular promise for type 2 diabetes. Women with type 2 diabetes who consumed 10 grams of inulin a day for two months had improvements in glycemic control and antioxidant levels.14

Increasing Your Movement Is Also Critical for Diabetes Prevention

It's also important to realize that inactivity in the form of extended sitting is one of the primary risk factors for insulin resistance and, ultimately, type 2 diabetes. The reason for this is because sitting shuts down or blocks a number of insulin-mediated systems, including muscular and cellular systems that process blood sugar, triglycerides and cholesterol. Standing up activates all of these systems at the molecular level.

Recent research15 also demonstrates that taking a 10-minute walk after each meal provides greater blood sugar control in diabetics than 30 minutes of exercise done once a day, lowering post-meal blood sugar levels by 22 percent. So, increasing the frequency of movement is an important component. Other recent research16 also reconfirms that the more you exercise, the lower your risk of type 2 diabetes. One of the reasons for this is that exercise allows your muscles to use sugar more effectively.

High intensity exercise will also increase nitric oxide production (as will sun exposure). Nitric oxide will relax your blood vessels, lower blood pressure, decrease platelet activation, and make your blood thinner and less likely to clot and form a stroke or heart attack. Nitric oxide will also improve your immune function.  Exercise will also increase brain derived neurotropic factor (BDNF) which is fertilizer for your brain cells and helps nourish and protect them from dementia-related changes.

Ketogenic Diet Improves Insulin Sensitivity

Another important strategy that can prevent or even reverse insulin resistance and/or type 2 diabetes is nutritional ketosis, which helps optimize your metabolic and mitochondrial function.

As a general guideline, a dietary intake of about 20 to 50 grams or even less per day of net carbs (total carbohydrates minus fiber) while also keeping protein low-to-moderate is usually low enough to allow you to make the shift to nutritional ketosis — the metabolic state associated with an increased production of ketones in your liver; i.e., the biological reflection of being able to burn fat.

To find your personal carb target, it's important to measure not just your blood glucose, but also your ketones, which can be done either through urine, breath or blood. This will give you an objective measure of whether or not you're truly in ketosis. Nutritional ketosis is defined as blood ketones that stay in the range of 0.5 to 3.0 millimoles per liter (mmol/L).

I explain the ins and outs of implementing this kind of diet, and its many health benefits, in my new book "Fat for Fuel." In it, I also explain why cycling through stages of feast and famine, opposed to continuously remaining in nutritional ketosis, is so important.

You actually need to have days where you eat more net carbs and more protein, especially with strength training, to prevent sarcopenia. After a day or two, you then cycle back into nutritional ketosis. Typically, this is done once a week. By periodically pulsing higher carb intakes, consuming, say, 100 or 150 grams of carbs, opposed to 20 to 50 grams per day, your ketone levels will dramatically increase and your blood sugar will drop.

Ketogenic Diet Reduces Your Risk of Alzheimer's Too

In a recent interview, Perlmutter shared core strategies to boost brain performance and dramatically reduce your risk of Alzheimer's. His own father actually died from Alzheimer's — a death he has since realized was preventable — which has acted as a driving force for his work.

"To be clear, no one inherits Alzheimer's. Some of us who have relatives [with] Alzheimer's … are at increased risk. We certainly know there are some genes, the apoliprotein E (ApoE) 3, 2 and 4 genes that are playing a role in carrying the ApoE-4 allele. It does increase a person's risk.

But this is not a determinant that you will or won't get the disease. It does indicate that you have a higher risk for that disease. But the beauty of what we are talking about is you can offset that risk. You can change your destiny," Perlmutter says.

A key strategy to do this is to eat a diet that powers your brain and body with healthy fats, not net carbs (total carbohydrates minus fiber). When your body burns fat as its primary fuel, ketones are created, which not only burn very efficiently and are a superior fuel for your brain, but also generate fewer reactive oxygen species and less free radical damage.

A ketone called beta hydroxybutyrate is also a major epigenetic player, stimulating beneficial changes in DNA expression, thereby reducing inflammation and increasing detoxification and antioxidant production.

A fascinating paper that demonstrates the power of diet and exercise for the prevention and treatment of Alzheimer's is that of Dr. Dale Bredesen, a UCLA researcher who, by leveraging 36 different healthy lifestyle parameters, was able to reverse Alzheimer's in 9 out of 10 patients. This included the use of exercise, ketogenic diet, optimizing vitamin D and other hormones, increasing sleep, meditation, detoxification and eliminating gluten and processed food.

His work was published in the journal Aging in 2014. You can download the full-text case paper online, which details the full program.17 According to Bredesen, "The results … suggest that, at least early in the course, cognitive decline may be driven in large part by metabolic processes."

Sun Exposure — Another Important Lifestyle Factor

Vitamin D and sun exposure are also important factors to consider. Research shows people living in northern latitudes have higher rates of death from Alzheimer's than those living in sunnier areas, suggesting a link between sun exposure and brain health. I also recently interviewed Dr. Lew Lim about the use of near-infrared light as a treatment for Alzheimer's, known as photobiomodulation.

About 40 percent of the rays in sunlight is near-infrared, which works by interacting with cytochrome c oxidase (CCO) — one of the proteins in the inner mitochondrial membrane and a member of the electron transport chain. CCO is a chromophore, a molecule that attracts and feeds on light. In short, sunlight improves the generation of energy (ATP). The optimal wavelength for stimulating CCO lies in two regions, red at 630 to 660 nanometers (nm) and near-infrared at 810 to 830 nm.

Photobiomodulation also improves oxygenation to your cells by releasing nitric oxide, is a vasodilator that helps relax your blood vessels, lower your blood pressure and improve vascular health. When you deliver red (660 nm) and infrared light (830 nm) to the mitochondria, it also promotes synthesizing of gene transcription factors that trigger cellular repair, and this is as true in the brain as anywhere else in your body.

Sunlight is a beneficial electromagnetic frequency (EMF) that is essential and vital for your health, Non-native or artificial EMFs, though, can be highly dangerous to your health and contribute to Alzheimer's by poisoning your mitochondria. This would be magnetic fields, electromagnetic interference (EMI) from the grid and microwave radiation from cellphone towers and Wi-Fi.

This is a very deep and important topic that I plan on greatly expanding later this year. I am convinced this is a major issue, but seeking to carefully compile an easy to understand solution to help remediate against these non-native EMFs. I am convinced enough now to never put my cellphone on my body unless it is in airplane mode, and I refuse to hold my cellphone unless it is on a selfie stick.

Also Mind Your Sleep Hygiene

Sleep is another factor that can play a significant role in your brain health, as your brain can only detoxify and clean itself out during deep sleep. If you have trouble sleeping at night, be sure to get bright sunlight exposure during the day, and avoid blue light sources at night, such as LED lighting, fluorescent lighting and electronic screens at night.

You can somewhat mitigate the negative impact of artificial lights and electronic screens in the evening by wearing blue-blocking glasses. I put on my orange-colored glasses as soon as the sun sets.

Also be sure to sleep in complete darkness. If you can see your hand in front of your face when you lie in bed, your bedroom is too bright. Recent research18 reveals even dim light exposure during sleep can affect your cognition the next day, specifically your cognition and working memory.

As you can see, while dementia is on the rise, and has few if any effective conventional treatments, you can significantly reduce your risk of this devastating disease by addressing lifestyle factors such as your diet, movement, sun exposure and sleep. For a list of additional lifestyle strategies that can help reduce your risk of Alzheimer's disease, please see "Alzheimer's: Every Minute Counts."


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