The Damaging Impact of Fructose on Our Brains

High-fructose corn syrup is ubiquitous in our food — it seems like it is in almost everything that is packaged, from soda to salad dressing.

In fact, officials from the Department of Agriculture estimate that Americans consumed an average of 27 pounds of high-fructose corn syrup in 2014.

And that much sugar is detrimental not only to our physical health, but our mental health as well.

Studies have shown that high-fructose damages communication between brain cells and increases toxic molecules in the brain. What’s more, a long-term high-fructose diet diminishes the brain’s ability to learn and remember information.

“Food is like a pharmaceutical compound that affects the brain,” said Fernando Gomez-Pinilla, a professor of neurosurgery and of integrative biology and physiology at UCLA.

But the good news is, Gomez-Pinilla and other researchers at UCLA may have found a countermeasure to mitigate that damage.

In a recent study, the UCLA researchers found that hundreds of genes in the brain can be damaged by fructose, leading to a myriad of diseases, from diabetes to Alzheimer’s disease to attention deficit hyperactivity disorder.

But the study also found that an omega-3 fatty acid known as docosahexaenoic acid, or DHA, seems to reverse the harmful changes produced by fructose.

“DHA changes not just one or two genes — it seems to push the entire gene pattern back to normal, which is remarkable,” said Xia Yang, a senior author of the study and a UCLA assistant professor of integrative biology and physiology. “And we can see why it has such a powerful effect.”

While DHA occurs naturally in the membranes of our brain cells, it is not in a large enough quantity to help fight diseases, especially those brought about by the high consumption of fructose in our packaged foods.

“The brain and the body are deficient in the machinery to make DHA, it has to come through our diet,” said Gomez-Pinilla, a co-senior author of the study.

Xia Yang and Fernando Gomez-Pinilla observed that after genes are altered by fructose, DHA seems to push the entire gene pattern back to normal. (Photo by Reed Hutchinson/UCLA)

DHA, which strengthens synapses in the brain and enhances learning and memory, is abundant in wild salmon (but not in farmed salmon) and, to a lesser extent, in other fish and fish oil, as well as walnuts, flaxseed, and fruits and vegetables, he noted.

For their study on the effects of fructose and DHA, the scientists trained rats to escape from a maze, and then randomly divided the animals into three groups.

For the next six weeks, one group of rats drank water with an amount of fructose that would be roughly equivalent to a person drinking a liter of soda per day. The second group was given fructose water and a diet rich in DHA. The third received water without fructose and no DHA.

The high fructose corn syrup in soda is detrimental to our brains. (Photo courtesy FreeImages.com/Jonathan King)

At the end of the six weeks, the rats were put through the maze again.

The rats that had been given only the fructose navigated the maze about half as fast as the rats that drank only water. This is an indication that the fructose diet had impaired their memory, according to the researchers.

In contrast, the rats that had been given fructose and DHA showed very similar results to those that only drank water. This strongly suggests that the DHA eliminated fructose’s harmful effects, the scientists report.

Other tests on the rats revealed more major differences: The rats receiving a high-fructose diet had much higher blood glucose, triglycerides and insulin levels than the other two groups.

Those results are significant because in humans, elevated glucose, triglycerides and insulin are linked to obesity, diabetes and many other diseases, according to the researchers.

The research team then sequenced more than 20,000 genes in the rats’ brains, and identified more than 700 genes in the hypothalamus — the brain’s major metabolic control center — and more than 200 genes in the hippocampus, which helps regulate learning and memory, that were altered by the fructose.

The altered genes they identified — the vast majority of which are comparable to genes in humans — are among those that interact to regulate metabolism, cell communication and inflammation, according to the researchers.

Conditions that can be caused by alterations to those genes include Parkinson’s disease, depression, bipolar disorder, and other brain diseases, said Yang.

Of the 900 genes they identified, the researchers found that two in particular — called Bgn and Fmod — appear to be among the first genes in the brain that are affected by fructose. Once those genes are altered, they can set off a cascade effect that eventually alters hundreds of others,  according to Yang.

While that’s a frightening fact, it also means that Bgn and Fmod are potential targets for new drugs to treat diseases that are caused by altered genes in the brain, she added.

The researchers also uncovered new details about the mechanism fructose uses to disrupt genes. They found that fructose removes or adds a biochemical group to cytosine, one of the four nucleotides that make up DNA. (The others are adenine, thymine and guanine.) This type of modification plays a critical role in turning genes “on” or “off.”

And while DHA appears to be beneficial in mitigating the damage fructose causes, it is not a magic bullet for curing diseases, according to Yang.

Instead, the researchers recommend avoiding sugary soft drinks, cutting down on desserts, and generally consuming less sugar and saturated fat.