6 in every 10 adults in the United States have a chronic condition; of those, 4 out of 10 have at least two, if not more. Alzheimer’s disease (AD) and diabetes (type 1 diabetes and type 2 diabetes) account for 2 of the 7 leading drivers of chronic disease. Additionally, overlap between the two is increasing; type 2 diabetes and Alzheimer’s (both which have historically been referred to as adult-onset conditions) are becoming more prevalent in people younger than 60.
To be clear, no one knows for certain what causes Alzheimer’s. But the prevailing theory -- the amyloid hypothesis -- continues to fall short. After multiple failed drug trials, the long standing theory is starting to crumble. Meanwhile, the idea that Alzheimer’s is somehow connected to diabetes (if not a diabetes of the brain entirely) continues to gain support.
Alzheimer’s disease continues to be referred to regularly as type 3 diabetes in academic and research papers. So much so that even mainstream media now uses both interchangeably.
And in those same papers, the scientists are presenting a common causality: insulin resistance.
The Role of Insulin in the Brain
Perhaps insulin’s most notable role is its ability to regulate blood sugar. But in reality, that’s just one other role this incredibly complex hormone plays. Among other jobs, insulin expresses itself in brain neurons.
Meaning, insulin is present in the brain to perform certain central nervous system roles. It’s still unclear how the insulin gets there: is it produced in the brain, or does it travel there? But it’s becoming extremely clear that insulin plays a hugely important role in overall brain function, a totally separate capacity from its blood sugar regulating role.
Insulin is vital to brain function (both directly in the brain itself, as well as indirectly as it relates to blood sugar stability). And where there is insulin, there’s the ability for insulin resistance, which is what many are now promoting as the primary cause for Alzheimer’s.
Alzheimer’s: Insulin Resistance of the Brain
Early on in Alzheimer’s, there are changes in the brain observed in studies that relate to energetics, or the brain’s ability to utilize fuel. Specifically, an Alzheimer’s brain is unable to utilize glucose (sugar) as a fuel source.
In one particular study, researchers found that the brain demonstrates a declining utilization of glucose long before Alzheimer’s begins to present itself, called brain-glucose hypometabolism. In this scenario, brain cells are not using glucose as a fuel source.
Long before someone experiences declining memory and other symptoms of Alzheimer’s disease, there is demonstrable change in the brain’s ability to use fuel. Similarly, people who have insulin resistance (as well as prediabetes and type 2 diabetes) have increased risk of developing Alzheimer’s.
A further look into insulin resistance gives way to higher-than-usual blood sugar levels. In fact, studies are showing a direct link in high blood sugar and cognitive decline: those with elevated blood levels had a faster rate of developing Alzheimer's than those with normal blood sugar, whether they technically had diabetes or not.
There’s a strong correlation, then, between insulin resistance, diabetes, high blood sugar, and Alzheimer’s, the common denominator being that the body is unable to correctly use glucose as a fuel source. If we take things a step further, the relationship is even more pronounced: insulin, in moderation and in balance, is vital to molecular balance (in brain activity, in glucose stability, and in other forms). But chronically elevated levels of insulin lead to insulin resistance (among other things).
When this happens in the brain, brain cells starve. While there may be plenty of glucose in the system, the brain cells have no way of accessing that energy source for fuel. This fuel shortage in the brain is what ultimately leads to memory loss and cognitive decline.
Big Picture: Eliminating Insulin Resistance
Whether dealing with diabetes or Alzheimer’s, or both, the preventative measure -- if not the fix -- is ridding the body of insulin resistance. Doing that depends mainly on diet.
We decrease insulin resistance by decreasing carbohydrate and sugar intake. In doing so, we minimize our chances of Alzheimer's.
Insulin resistance is caused by chronic and increased levels of insulin in the body. In the same way that drug tolerance exists, so does insulin tolerance (it’s the same as insulin resistance). Higher and higher doses of insulin are needed over time to achieve the desired effect (blood sugar regulation) until it simply no longer works.
But why is all that insulin needed? It’s carbs, sugar, and the western lifestyle.
Foods that instigate a substantial uptick in insulin (whether from the pancreas or from a needle) cause insulin resistance; they also cause elevated blood sugars.
Bread, grains, and sugar (in all its forms, including fruits) create a desperate need for higher insulin levels. But foods that are high in healthy fats and protein require little to no insulin, resulting in no insulin resistance, which could mean no Alzheimer’s.
The cognitive decline recognized in Alzheimer’s is not a disease in itself; it’s the result of chronic insulin resistance of the brain, to the point that the brain is no longer able to heal or protect itself.
By eliminating carbohydrates -- ones that require high levels of insulin in order to stabilize blood sugar like candy bars, energy bars, pasta, pizza, fruit juices, soda, cereal, potatoes, rice, crackers, bread, beans, corn, and so much more -- insulin resistance is lowered, resulting in lower chances of both Alzheimer’s and type 2 diabetes.