The connection between blood sugar and Alzheimer's disease


Go back to your time with those hunters and gatherers. Their brains are not very different from yours. Both have evolved to seek foods high in fat and sugar. After all, it is a survival mechanism. The problem is that your hunting efforts end quickly because you live in the age of plenty, and you are more likely to find processed fats and sugars. Your caveman colleagues are likely to spend a lot of time looking, just to find animal fat and natural sugar from wild plants and berries if the season is right (and these plants and berries are far less sugary than you think when you think of fruit). So while your brain can function similarly, your sources of nutrition are anything but. In fact, take a look at the following chart, which describes the main differences between our diet and that of our ancestors. And what, exactly, does this difference in eating habits have to do with how well we age and whether or not we suffer from a neurological disorder or disease?


Studies that describe Alzheimer's as a third type of diabetes began to emerge in 2005, but the link between poor diet – notably a high-carbohydrate – and Alzheimer's disease has only recently focused on more recent research showing how this it may happen.

These studies are compelling and exciting at the same time. Thinking we can prevent Alzheimer's by just changing the food we eat is, well, open our eyes. This has many implications for preventing not only Alzheimer's disease, but all other brain disorders, as you'll discover in the next few chapters. But first, a brief lesson on what diabetes and brains have in common. The nickname "type 3 diabetes" sounds a bit confusing at first, but all types of diabetes share one common feature: a bad relationship with insulin, one of the body's most important substances for cellular metabolism.

Evolutionarily, our bodies have designed a brilliant way to turn food fuel into energy for our cells to use. For almost the entire existence of our species, glucose – the body's primary source of energy for most cells – has been scarce. This has led us to develop ways to store glucose and convert other things into it. The body can manufacture glucose from fat or protein, if necessary, through a process called gluconeogenesis. But this requires more energy than the conversion of starches and sugar into glucose, which is a more direct reaction.

The process by which our cells accept and utilize glucose is elaborated. The cells do not just suck the glucose that passes through them into the bloodstream. This vital sugar molecule needs to be released into the cell by insulin, which is a hormone produced by the pancreas. His job is to transport glucose from the bloodstream to muscle, fat and liver cells. Once there, it can be used as fuel. Normal and healthy cells have high insulin sensitivity. But when cells are constantly exposed to high levels of insulin as a result of a persistent intake of glucose (much of it is caused by excessive consumption of hyperprocessed foods full of refined sugars that raise insulin levels beyond a healthy limit ), our cells adapt by reducing the number of receptors on their surfaces to respond to insulin. In other words, our cells desensitize to insulin as if they were revolting against their flood. This causes insulin resistance, which allows cells to ignore insulin and not recover glucose from the blood. The pancreas then responds by pumping more insulin. Therefore, higher insulin levels are required for sugar to enter cells. This creates a cyclical problem that culminates in type 2 diabetes. By definition, people with diabetes have high blood sugar levels because their body can not carry sugar into the cells where it can be stored safely for energy. And this blood sugar presents many problems – many to mention. As a poisonous poison, toxic sugar causes a lot of damage, leading to blindness, infections, nerve damage, heart disease and, yes, Alzheimer's and even death. Throughout this chain of events, the inflammation runs loose in the body.

I should also point out that insulin can be seen as an accomplice to events that occur when blood sugar can not be well administered. Unfortunately, insulin does not just drive glucose into cells. It is also an anabolic hormone, which means it stimulates growth, promotes fat formation and retention and stimulates inflammation. When insulin levels are high, other hormones may be adversely affected, increased or decreased due to the dominating presence of insulin. This, in turn, plunges the body further into sickly patterns of chaos that undermine its ability to regain its normal metabolism.

Genetics is certainly involved in whether or not a person becomes a diabetic, and genetics can also determine at what point the body's diabetes exchange is activated, since its cells can no longer tolerate high blood sugar . For the record, type 1 diabetes is a separate disease, considered an autoimmune disorder, accounting for only 5% of all cases. People with type 1 diabetes produce little or no insulin because their immune system attacks and destroys the pancreas cells that produce insulin, so daily injections of this important hormone are needed to keep blood sugar balanced. Unlike type 2, which is usually diagnosed in adults after their bodies have been abused for excess glucose over time, type 1 diabetes is typically diagnosed in children and adolescents. And unlike type 2, which is reversible through changes in diet and lifestyle, there is still no cure for type 1, although it can be administered relatively well through both drugs and diet. That said, it is important to keep in mind that although genes strongly influence the risk of developing type 1 diabetes, the environment may also play a role. Type 1 has long been known to result from both genetic and environmental influences, but the increasing incidence in recent decades has led some researchers to conclude that environmental factors could be more instrumental in type 1 development than previously thought.

What we are beginning to understand is that at the root of "type 3 diabetes" is the phenomenon in which brain neurons become incapable of responding to insulin, which is essential for basic tasks, including memory and learning. We also believe that insulin resistance, as it relates to Alzheimer's disease, can trigger the formation of these infamous plaques present in diseased brains. These plaques are the buildup of a foreign protein that essentially sequesters the brain and takes the place of normal brain cells. Some researchers believe that insulin deficiency is critical to the cognitive decline of Alzheimer's disease – brain cells can not get insulin because they are resistant to it! And the fact that we can associate insulin resistance with brain diseases is why the talk about "type 3 diabetes" is beginning to circulate among researchers. It is even more important to note that obese people are at a much higher risk of impaired brain function, and that those with diabetes are at least twice as likely to develop Alzheimer's disease. And those with pre-diabetes or metabolic syndrome – a set of biochemical abnormalities associated with the development of type 2 diabetes as well as cardiovascular disease – have an increased risk of pre-dementia or mild cognitive impairment (MCI), which usually progresses to complete disease of Alzheimer's disease.

This statement is not meant to imply that diabetes directly and always causes Alzheimer's disease, only that they share the same origin. Both are often born from over-consumed foods that force the body to develop biological pathways that lead to dysfunction and, later, disease. While it is true that a person with diabetes and someone with dementia may look and act differently, it has much more in common than we previously thought. And what I find really interesting (and I mentioned earlier) is that more recent studies are showing that people with high blood sugar – whether or not they have diabetes – have a higher rate of cognitive decline than those with normal levels of blood sugar. This was true in a particularly disturbing longitudinal study from 2018, tracking more than 5,000 people in 10 years. Their rate of cognitive decline – regardless of whether or not they were diabetic – depended on blood sugar levels. The higher the blood sugar, the faster the decline – even in non-diabetics.

In the last 20 years, we have seen a parallel increase in the number of cases of type 2 diabetes and in the number of people considered obese. Now, however, we are beginning to see a pattern among those with dementia, too, as the rate of Alzheimer's disease increases in synchrony with type 2 diabetes. I do not think this is an arbitrary observation. It is a reality that we all have to face as we bear the brunt of rising health care costs and an aging population. New estimates indicate that Alzheimer's disease will more than triple the prevalence and is likely to affect 16 million Americans by 2050, a crippling number for our health system and one that will overcome our obesity epidemic. There were about 50 million people worldwide living with dementia in 2017, and that number will almost double every 20 years, reaching 75 million in 2030 and 131.5 million in 2050. Today in the United States, someone develops dementia of Alzheimer's every 66 seconds. By the middle of the century, someone in the United States will develop the disease every 33 seconds (remember, someone in the world develops dementia every 3 seconds). The prevalence of type 2 diabetes, which accounts for 90-95% of all cases of diabetes in the United States, has tripled in the last 40 years, and millions of people have gone unnoticed and untreated for a long time. By the definition of either, this is absolutely an epidemic. No wonder the US government is eager for researchers to improve the prognosis and avoid a catastrophe. According to the Centers for Disease Control and Prevention (CDC), more than 30 million people have diabetes, which is equivalent to almost 10% of the US population; other reports have calculated that the percentage of adults is more than 12% to 14%, depending on the criteria used. It is estimated that 7.2 million adults, 18 years or older, are not diagnosed (23.8% of people with diabetes).

Extracted from Grain Brain (revised edition) Copyright © 2018 by David Perlmutter, M.D. and Kristin Loberg. Used by permission of Little, Brown and Company, New York. All rights reserved.


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