Consuming too much sugar might cause dementia, studies suggest

Ancient survival instinct might be driving the onset of Alzheimer’s disease

New research reveals that too much fructose—a form of sugar—in the brain might lead to Alzheimer’s disease.

The study offers a new way of looking at the ailment, which is characterized by more than normal amounts of certain proteins in the brain. These proteins slowly cause cognition and memory to erode.

The scientists who undertook the study at the University of Colorado School of Medicine suggest that this new study underlines their belief that Alzheimer’s disease is driven by diet.

In this case, clearly, the over-consumption of sugary foods could be a major culprit.

Their contention is supported by other research that has found that people who have diabetes are twice as likely as others to develop dementia.

Diabetes drug reduces dementia risk

Now another new study has found that people with type 2 diabetes who take the affordable diabetes drug pioglitazone—sold under the brand name Actos—were less likely to develop dementia later in life than those who did not take the drug. That study was conducted at Yonsei University in Seoul, Korea.

Researchers working with the American Academy of Neurology say the drug Actos helps control blood sugar levels by boosting insulin.

Convincing evidence

Taken together, these studies appear to produce convincing evidence that consuming too much sugar might make a person more likely to suffer from Alzheimer’s disease later in life.

Because dementia develops for years before it is diagnosed, an opportunity might be present for taking steps before it progresses, says Dr. Eosu Kim of Yonsei University.

Adaptation of a foraging instinct

In the University of Colorado study, the researchers explain that Alzheimer’s might be a damaging adaptation of a foraging instinct that was present in our ancestors. This survival pathway relied on the sugar fructose, explains Dr. Richard Johnson, a professor at the university’s School of Medicine who specializes in kidney disease and high blood pressure.

He explains that a basic principal of life is to ensure that we have enough water, food, and oxygen for survival.

Foraging for food to avoid starvation depended on rapid assessment, focusing, being impulsive, exploring, and taking risks. In this scenario it is helpful, Johnson notes, to block out whatever gets in your way, such as attention to time and recent memories, while you are out searching for food.

Dampens brain centers

Fructose plays a role by dampening these centers of the brain, enabling the brain to focus more on gathering food. This happens whether the person produces or eats their own fructose.

When it is processed by the body, fructose, and its by-product uric acid, becomes essential to animal and human survival, the researchers explain.

Fructose limits the flow of blood to the brain’s cerebral cortex—which is involved in self-control—as well as the thalamus and hippocampus. At the same time the flow of blood increases in the visual cortex, a region of the brain that is associated with food reward.

These actions in the brain were helpful in food foraging, but when food was found and the foraging was over the brain returned to its normal functioning, Johnson explains.

Survival switch remains on

Fructose in the brain served as a “survival switch,” he says, that was turned on by the fructose in the brain and then was turned off.

Today, however, we consume a lot more fructose through over-eating foods that are sugary, high in fat, and salty. That causes an excess production of fructose that puts the survival switch into an “always on” position. That, in turn, is damaging to the brain.

Tests on rats

A study found that if laboratory rats are fed fructose long enough they develop amyloid beta and tau proteins in the brain. These are the same proteins that are seen in Alzheimer’s disease, Johnson says.

You also find high levels of fructose in the brains of people who suffer from Alzheimer’s.

In addition, Johnson suggests, the tendency of some Alzheimer’s patients to wander off also could be linked to the ancient foraging response.

Johnson suggests that pharmacological and dietary tests should be held to determine whether these findings can lead to a potential benefit in the management, prevention, and treatment of this disease.

The study appears in the American Journal of Clinical Nutrition.

How Korean study was conducted

In the Korean study, researchers used the Korean health database to find people diagnosed with type 2 diabetes who did not have dementia at the start of the study. These people were followed for an average of 10 years.

Those who used the diabetes drug for four years were a third less likely to develop dementia than those who did not take the drug.

For those who also had a history of stroke and heart disease the risk of dementia was reduced by about half.

In previous studies those who took the drug, but did not have diabetes, were not protected from dementia any more than anyone else. A vital factor, therefore, was the presence of diabetes.

The Korean study appears in the journal Neurology.

The studies indicate that the over-consumption of sugary products leads to diabetes and also to Alzheimer’s. The drug sold as Actos lessens the effects of diabetes and therefore lowers the risk of dementia.