Sugar in Processed Foods and Drinks Linked to Dementia; Experts Explain Possible Reasons

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The exact causes of Alzheimer’s disease are still being investigated, but a growing body of research suggests that a common sweetener may play a role.

High-fructose corn syrup (HFCS) is a sweetener commonly used in processed foods and beverages. It’s made from corn starch and is typically used as a substitute for sucrose (table sugar) because it’s cheaper and more shelf-stable.

A study published in June 2022 in the Public Library of Science found that rats consuming HFCS from a young age developed adverse changes in parts of the brain responsible for memory, emotion, and nervous system function. Eating HFCS long-term resulted in a prolonged reduction in metabolism in these brain regions, causing degeneration and cognitive decline typical of Alzheimer’s disease.

A March 2023 review of studies published in The American Journal of Clinical Nutrition also states that fructose may reduce metabolism in brain regions involved in higher cognitive functions.

The researchers involved in the review theorize that increased fructose levels in the brain may increase our risk for Alzheimer’s disease.

However, they also emphasize that the consumption of glucose (a component of sucrose) and high glycemic index foods plays the greatest role in increasing fructose levels in the brain. A 2017 Yale study discovered that fructose can be created from glucose in the brain.

The current review’s lead author, Dr. Richard Johnson, cited earlier research that found that laboratory rats fed fructose for long enough develop tau and amyloid beta proteins in the brain. These proteins are linked to Alzheimer’s.

“We make the case that Alzheimer’s disease is driven by diet,” Johnson, a professor at the University of Colorado School of Medicine specializing in renal disease and hypertension, said in a statement.

Johnson suspects that a response he calls the “survival switch,” which helps humans survive during times of food scarcity, is stuck in the “on” position in a time of abundant food. This leads to overeating high-fat, sugary, and salty food, which prompts excess fructose production.

He suggests that dietary and pharmacologic trials to reduce fructose exposure or block fructose metabolism should be performed to find if there’s a benefit that will aid in the prevention, management, or treatment of Alzheimer’s disease. There is still limited research and insight into the roles fructose metabolism plays in the brain.

Fructose Changes Brain Metabolism

Fructose consumption has increased significantly because of the extensive use of HFCS in beverages and processed foods.

This sweetener has also been shown to cause negative health effects, especially diabetes.

“Research has suggested Type 2 diabetes can be a risk factor for Alzheimer’s disease and other types of dementia, like vascular dementia,” Claire Sexton, who holds a doctorate in psychiatry from the University of Oxford and is the Alzheimer’s Association senior director of scientific programs and outreach, told The Epoch Times.

She explained that this could be because the factors that increase the risk of Type 2 diabetes have also been shown to increase the risk of dementia. It could also be a result of the long-term effects of impaired sugar metabolism in the brain, which leads to low blood sugar, since the brain needs blood sugar to stay fueled.

In a double-blind study at the University of California–Davis, researchers observed increased liver fat and reduced insulin sensitivity in two groups that drank either three HFCS-sweetened or three sugar-sweetened beverages daily for only two weeks.

This doesn’t mean that eating fruit is bad for our health. Fructose is only harmful in excess amounts, and fruit contains small amounts compared with many processed foods.

Fruits are also packed with nutrients and fiber that help us maintain a balanced diet that encourages good health.

The problem is our consumption of free sugars—fructose, glucose, and sucrose that are separated from their naturally occurring source. This includes sugars that are added to food and drinks during commercial processing.

Evidence shows that the health risks from sugars are related to consuming too many free sugars in the diet, not from eating sugars that are naturally present in foods such as fruits and milk.

Is Alzheimer’s Disease a 3rd Type of Diabetes?

Scientists report a close association between Type 2 diabetes and Alzheimer’s, pointing out that Alzheimer’s disease is twice as frequent in diabetic patients. One popular theory suggests that Alzheimer’s may be a metabolic disorder, similar to Type 2 diabetes, in which the body is unable to properly process insulin.

Studies show that insulin plays a critical role in brain function, and insulin resistance in the brain plays a role in cognitive decline.

A study published in Frontiers in Neuroscience in 2021 found that diabetic hyperglycemia (high blood sugar) can directly result in brain hyperglycemia. This may cause the blood-brain barrier to adapt by letting in less glucose, which the brain needs to function. The researchers concluded that brain hyperglycemia provides a plausible explanation for the well-documented link between Alzheimer’s disease and diabetes.

There has been a growing interest in the idea that Alzheimer’s disease may be a third type of diabetes. However, this theory has sparked disagreement about whether it’s really how the disease develops.

Sexton said she doesn’t think Alzheimer’s is diabetes, and that suggesting they’re the same doesn’t account for the complexity of either disease.

“While studies have shown a link between insulin resistance and risk of developing Alzheimer’s disease, the condition can still develop without the presence of excessive glucose in the brain,” Sexton said.

When asked if treating insulin resistance could potentially reduce Alzheimer’s risk, she said the idea is currently being explored in clinical trials.

“In fact, last year at the Alzheimer’s Association International Conference, T3D Therapeutics reported positive interim results from their phase 2 trial of T3D-959, which seeks to overcome insulin resistance in the brain and restore its metabolic health.”