For decades, scientists have fixated on amyloid beta plaques as the villain behind Alzheimer’s disease, but mounting evidence suggests they may have been chasing a red herring. Now, a groundbreaking theory from leading researchers is making waves: Could a sweet but sinister culprit be the real driver of this devastating condition? This new hypothesis sheds light on how a survival mechanism gone awry may be wreaking havoc on modern brains, potentially redefining how we understand—and combat—Alzheimer’s.
Key Takeaways
- Excessive fructose intake disrupts brain metabolism, contributing to neuron dysfunction and damage.
- Fructose could be the underlying factor tying together amyloid beta plaques, tau tangles, and other mechanisms previously blamed for Alzheimer’s.
- High fructose consumption is linked to diseases like obesity, diabetes, ADHD, and heart disease, emphasizing the need to be careful with your diet.
What's Behind Alzheimer's Disease?
Scientists have focused on amyloid beta plaques as the primary cause of Alzheimer’s disease for more than 25 years.
Readers of this publication know I tossed the theory out a long time ago.
For one thing, autopsies reveal that quite a few people who died with dementia don’t have the plaques.
In addition, a great many trials of drugs aimed at treating amyloid have failed to heal the disease, leading even those geniuses in mainstream medicine to wonder if it's time to explore other avenues.
Among the possible candidates are the role of insulin, inflammation, and free radicals.
Now, a factor has been proposed that combines many of these other factors to create one underlying cause of the disease.
This theory is sure to be controversial in the U.S., because it suggests that Alzheimer’s disease is caused by sugar, specifically fructose.
This novel proposal has been put forward by an interdisciplinary team of neurologists, neuroscientists, and other experts from the University of Colorado Anschutz Medical Campus. It was published in the journal Frontiers of Aging Neuroscience2.
Fructose is Unique Among Nutrients
The researchers recount how humans evolved on a diet containing very little sugar, yet today, sugar accounts for around 15 to 20 percent of all calories consumed in modern diets. And I daresay that sugar accounts for a lot more calories than that in the Western diet!
The consumption of one type of sugar, fructose, has soared partly thanks to high fructose corn syrup found in 70 percent of processed foods like sodas, candy, cookies, muffins, crackers, salad dressings, ketchup, prepackaged meals, and much else. The theory suggests this growth in fructose intake over time has led to excessive and chronic activation of a "survival" pathway in the brain that is the driving force behind Alzheimer's disease. "In essence, we propose that Alzheimer's disease is a modern disease driven by changes in dietary lifestyle in which fructose can disrupt cerebral metabolism and neuronal function," explains lead author Richard Johnson, M.D.
"Fructose," the authors write in their paper, "is unique among nutrients because it activates a survival pathway to protect animals from starvation..."
Fructose and Your Brain’s “Survival” Pathway
Many animals rely on fruit, with its fructose content, to protect themselves during winter when there's little food around.
Fructose can put the animal’s body in survival mode. The compound lowers cellular energy production in the mitochondria, which in turn encourages foraging behavior, higher food intake, and fat storage while decreasing the body’s requirement for oxygen. Fructose triggers insulin resistance to reduce glucose uptake in the muscles and increase glucose in the blood to fuel the brain.
This temporary emergency response keeps animals alive.
In humans, the fructose pathway was also needed for survival at different times in our evolution. But a 40-fold increase in fructose consumption has occurred over the last 300 years.
Since the body can manufacture its own fructose, this massive expansion has slowly increased the expression and activity of enzymes involved in the endogenous or internal production and metabolism of cerebral fructose.
The brain now produces fructose at a higher rate than in the past.
This bears repeating: Your body and your brain is producing fructose in addition to what you’re consuming in your diet.
The Link Between Fructose and Alzheimer’s Progression
The authors demonstrate that fructose overconsumption triggers the lowering of cellular energy within the brain and leads to a series of events that render brain neurons unable to function.
The events include poor glucose metabolism and the development of insulin resistance, a loss of mitochondria, increased free radical production, higher levels of ammonia, and the production of pro-inflammatory uric acid.
As a result, the brain goes on to produce amyloid beta and tau tangles as a protective mechanism against these insults, but ultimately, the tangles cause damage, leading to the death of brain cells. Amyloid and tau, therefore, "are not the central factors driving the disease," say the authors.
Fructose, they believe, acts as a unifying hypothesis encompassing prior theories put forward to explain the development of Alzheimer's. In other words -- if the theory can be confirmed -- fructose is THE cause behind all of the reasons put forth to date for the development of Alzheimer’s disease.
The scientists cite existing evidence that dietary intake of fructose is linked to cognitive dysfunction in both animals and humans and that fructose metabolism is active in Alzheimer's patients.
They also show that health problems caused by fructose go well beyond Alzheimer's.
Linked to a Wide Range of Diseases
The researchers point to behavioral disorders such as ADHD and aggression that have been linked to fructose consumption. Or the obesity epidemic that can be connected to fructose overconsumption leads to increased fat storage in the body.
The resulting insulin resistance caused by fructose leads to diabetes. And, of course, there’s cancer, which can happen as fructose decreases the body’s energy and oxygen requirement.
Fructose also triggers changes in the vascular system that cause high blood pressure, heart failure, stroke, and atherosclerosis.
Is there anything we can do if our brains produce more fructose than in the past?
The authors provide no answer, but the easiest one is apparent: avoid all food and drinks containing high fructose corn syrup as if your life depended on it. Because it probably does.
What About Fruit?
In an interview earlier this year, Dr. Johnson explained that many fruits, like apples and strawberries, have low levels of fructose. Still, they also contain beneficial compounds like fiber, vitamin C, flavonols, and antioxidants.
Interestingly, many of these valuable compounds neutralize the ability of fructose to store fat. So, eating a modest amount of fruit can be very healthy. However, consuming large amounts of fruit, especially in dried or juice form, is not a good idea.
My Takeaway
I’m not surprised by this research. It’s very much in line with what we’ve published for years.
I’ve long reported on the link between a diet rich in fructose-laden processed foods and diseases like Alzheimer’s, obesity, diabetes, heart disease, and cancer. In my opinion, this new study is just another nail in the coffin for the Western diet.
Most importantly, it’s additional motivation for you to make food choices that are natural, fresh, and nutrient-rich-- instead of processed-- and are low in all kinds of carbs (not merely fructose).
Summary
A provocative theory proposes that fructose, a type of sugar increasingly abundant in modern diets, could be the primary driver behind Alzheimer’s disease. Researchers suggest that fructose activates a “survival” pathway in the brain, designed to protect against starvation, but when overstimulated by excessive consumption, it disrupts brain metabolism and triggers neuron damage. This discovery could unify prior theories about the disease’s origins and highlight the critical role of dietary choices in preventing not only Alzheimer’s but a host of other chronic diseases.
Frequently Asked Questions
What is the theory about fructose and Alzheimer’s?
Researchers suggest that excessive fructose consumption disrupts brain metabolism, potentially driving Alzheimer’s disease.
Why is fructose considered unique among nutrients?
Fructose activates a survival pathway that was beneficial during food scarcity but harmful when overstimulated in modern diets.
What foods are high in fructose?
Primary sources are processed foods containing high fructose corn syrup, such as sodas, candy, and prepackaged meals.
How does fructose consumption impact overall health?
It’s linked to Alzheimer’s, obesity, diabetes, heart disease, and behavioral disorders like ADHD.
Can eating fruit be harmful?
Whole fruits, in moderation, are healthy due to their fiber and antioxidants, but consuming large amounts, especially dried fruit or juice, may pose risks.
