Insulin resistance speeds up cognitive decline

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 research4,5,6strengthens 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.

By Dr. Mercola