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Can Eating Sugar Cause Dementia? A Plain-English Explanation

Photo: Two cupcakes with blue and yellow frosting

Eating sugary foods could give you dementia.?This is bad news if you’re a sweet tooth. The good news is that changing what you eat can improve your brain health.

Age and genetics are risk factors for dementia that you have no control over. You can change your diet to increase energy in the short-term, and brain health in the long-term.

Recently, research has been looking at how blood sugar affects brain health. People with high blood sugar levels have higher rates of Alzheimer’s disease.

Why is Alzheimer’s Called Type 3 Diabetes?

Both type 1 and type 2 diabetes results in high blood sugar levels. Studies have shown that, compared to the general population, aging people with diabetes have:

  • Poorer memory
  • Slower recall
  • Higher levels of cognitive decline
  • Double levels of Alzheimer’s

Alzheimer’s disease has been referred to as a type 3 diabetes. There is a faster rate of cognitive decline in people with chronic high blood sugar levels. Up to 80% of people with Alzheimer’s disease have insulin resistance.

5 Ways High Blood Sugar Can Damage The Brain

1. A Dangerous Cycle of Insulin Resistance

Poor insulin control appears to be a risk factor for Alzheimer’s disease.

When you eat food, the carbohydrates, starches and sugar in your food are broken down into another type of sugar (glucose). As your body digests the food, the stomach and small intestine absorb the sugar and send it into your bloodstream.

Read: Stop Eating “Lazy Foods” and Get More Energy

The hormone insulin pulls sugar from the bloodstream and gives it to cells?in the organs and muscles. This gives your cells energy. The pancreas is the large gland that creates the hormone insulin.

If your blood sugar levels are too high your body releases more insulin. So, the insulin is trying to give MORE sugar to cells.?Your cells will try to protect themselves from the powerful effect of insulin. They do this by becoming insulin resistance.

The pancreas responds to this resistance by releasing more insulin. This starts a dangerous cycle.

Eating sugary and high-carbohydrate foods causes high blood sugar. The body tries to control this onslaught of sugar by pumping out a lot of insulin quickly. This is an “insulin spike.”

Over time, high insulin causes cells to become resistant to insulin. Insulin resistance leads to higher blood sugar levels. High blood sugar levels cause more insulin to be released. Another dangerous pattern emerges.

2. Drowning The Brain in Sugar

Your brain requires a constant source of energy in the form of glucose (this is sugar once it’s digested in your body). In the brain, glucose can easily enter the brain cells.

Unlike other cells in the body, brain cells do not need insulin to absorb sugar. So brain cells will absorb sugar directly from the bloodstream. Sugar crosses the blood-brain barrier easily.

However, now that there is sugar flowing through the brain, it doesn’t produce mental energy. Only with insulin can the brain convert sugar into energy.

If years of eating sugars and simple carbohydrates have resulted in insulin resistance, then the brain has high levels of both insulin and sugar. The high load of insulin is trying to prevent the brain from using the sugar and converting it into energy. The brain is almost swimming in sugar, but can’t use the sugar and can’t convert it to energy — the energy to regulate body functions and help us think.

If the brain cells can’t get the energy they need (from sugar), then they die. The sad irony is that, with insulin resistance, the brain cells are surrounded by sugar, and are almost drowning in it… they just can’t use the sugar.

3. High Blood Sugar Causes Inflammation

High blood sugar also causes inflammation in your body. Inflammation has been linked with

  • Heart disease
  • Diabetes
  • Cancer
  • Alzheimer’s disease

Eating a diet high in sugar and simple carbohydrates leads to inflammation. This often happens as excess fat is stored around the abdomen. Abdominal fat releases cytokines, a type of protein that causes inflammation.

Inflammation on the inside of the body is similar to an infected cut on your skin: it is red, swollen and filled with puss.?Inflammation in internal organs, such as the heart or brain, puts the body in a constant state of “fighting infection.” This cause your cognition to break down, as the brain and the blood vessels running through it are swollen and irritated.

4. Sugar Clogs the Brain

The large amount of abdominal fat in obese people double’s a person’s risk of Alzheimer’s. This is because obese people have “clumps” in their brains that literally clog thinking. How?

Amyloid proteins are toxic to the brain. Obese people have higher levels of amyloid proteins. When there are a lot of amyloid proteins, they stick together and form clumps. These clumps are found in brains of people with Alzheimer’s disease.

In the medical world, there is ongoing debate about whether amyloid protein clumps cause Alzheimer’s, or do not cause the disease but are in the brain of people with Alzheimer’s.

5. High Blood Sugar Causes Strokes

Insulin resistance affects the flow of blood to the brain. When brain cells don’t get enough blood, brain function suffers.

A decrease in blood flow can lead to mini strokes. High blood sugar levels can also make the blood vessels weak, like old leaky pipes.
Strokes are one of the factors in developing dementia.

Protect Your Brain, Protect Your Future

A high functioning brain is one of the keys to a high quality of life. Protecting your brain from damage?is important.

Dementia can be a frightening disease. Wouldn’t you want to lower your risk of dementia? There any many factors that contribute to dementia. Some of the factors are in your control.

Insulin resistance is thought to cause a cascade of problems in your brain. Over half of the U.S. population is likely to be insulin resistant. The good news is that insulin resistance is both preventable and treatable.

You can learn more about how you can protect your brain from the harmful effects of sugar. In the upcoming Part II of this blog post, you can discover 4 key strategies to keep your brain healthy.


  1. Diabetes Linked to Worse Cognition in Aging Patients
  2. Avoiding Alzheimer’s Disease Could be Easier Than You Think
  3. The Startling Link Between Sugar and Alzheimer’s
  4. Alzheimer’s Association: Diabetes and Cognitive Decline
  5. American Diabetes Association: Glycemic Index and Diabetes
  6. Inflammation: An Unifying Theory of Disease?

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About The Author

Crystal Jo is a Registered Nurse who is passionate about helping older adults live happy, healthy lives at home. As a freelance writer, she enjoys educating and inspiring seniors, and those who love them, to choose a healthy life.