Fructose, the ubiquitous sweetener in the American diet, alters genes that are linked to a variety of diseases, including diabetes, heart problems, attention deficit hyperactivity disorder (ADHA), and Alzheimer’s disease, according to new research.
A research team at the University of California, Los Angeles (UCLA) has performed the first genomics study into the genes and networks affected by fructose consumption.
They also looked at how the sweetener affects the regions of the brain that deal with metabolism as well as memory and learning.
They found, however, more evidence to suggest diets rich in omega-3 fatty acids can help protect against the detrimental effects of fructose.
Xia Yang, a UCLA assistant professor of integrative biology and physiology, and Fernando Gomez-Pinilla, a UCLA professor of neurosurgery and of integrative biology and physiology, were the senior researchers of the study.
“The main aspect of this study is how fructose contributes to disease,” Gomez-Pinilla told Healthline.
“We see the damaging effects of fructose, but why?” Yang added in an interview with Healthline.
Where is Fructose Found?
The researchers’ findings, published in the journal EBioMedicine, add to the growing evidence that the sweetener-rich American diet may be contributing to rising health concerns in the United States and other areas that have adopted the diet.
Fructose appears naturally in fruits, vegetables, and honey, but it is also added to processed foods — via table sugar, high-fructose corn syrup, and other sweeteners — to make them more palatable.
They’re most often consumed in desserts, sweetened beverages, including fruit juice, and lesser known sources, like breads, condiments, and flavored yogurts.
According to the U.S. Department of Agriculture, the average American consumed 27 pounds of high-fructose corn syrup in 2014. That’s nearly eight teaspoons a day, resulting in an extra 127 nutrition-less calories.
Effects on Memory
The UCLA team trained rats to escape from a maze and then divided them into three groups.
For six weeks, one group received fructose in their water comparable to a person drinking a liter of soda a day.
Another group was given the same amount but also a diet rich in the omega-3 fatty acid docosahexaenoic acid (DHA), like that found in wild salmon.
The third group was given neither fructose nor DHA.
The rats were again put in the maze they’d memorized before.
The rats with the soda-simulating diet traversed the maze at about half the speed of those without any fructose. The rats with DHA and fructose, however, escaped the maze in about the same time as those given no fructose.
This, the researchers say, suggests the DHA may mitigate the memory-dampening effects of the fructose.
Besides slower maze navigation skills, the rats on the fructose-only diet had higher blood sugar levels, triglycerides, and insulin levels.
These are important, the researchers said, because those symptoms in humans are linked to obesity, diabetes, and other diseases.
The effects of the fructose-heavy diets lasted for about two to three months, but the rats didn’t fully recover.
“We don’t know how permanent it can be,” Gomez-Pinilla said.
How It Affects the Brain
The team then sequenced more than 20,000 genes from the rats’ brains and found two genes in particular, BGN and FMOD, which were first affected by fructose.
These altered genes can set off a chain reaction affecting other genes, the majority of which are similar to genes in humans that affect metabolism, communication between cells, and inflammation.
Specifically, the researchers added, these altered genes can cause Parkinson’s disease, depression, bipolar disorder, and other brain disease.
Fructose also altered hundreds of genes in the hypothalamus and hippocampus, areas of the brain responsible for controlling metabolism, learning, and memory.
“Fructose must play a role in these diseases, in the way they’re expressed in the genes,” Yang said.
To replicate such a test in humans, Gomez-Pinilla said, would be both expensive and exhaustive, but there’s already a “strong linkage” that a fructose-heavy diet contributes to disease in humans.
“Here we are talking about sugar and DHA, but there are many more components in a person’s diet that can be good or bad,” he said.
Little Sugar, Lots of Omega-3s
When Yang came from the United States, she couldn’t eat the desserts because they were too sweet for her palate.
The same goes for fruit juice, which has had all the necessary fiber stripped from it that would help slow the body’s processing of its high sugar content.
“Basically, you’re just drinking sugar,” she said. “Here, you find sugar is in nearly every food.”
As every person’s diet is different, pinpointing a single way to eat healthy can be difficult.
The levels at which sugars appear in the Western diet, however, may help explain the rise of preventable diseases like obesity, type 2 diabetes, heart disease, and nonalcoholic fatty liver disease, a condition where the liver creates excess triglycerides in response to fructose.
These effects shouldn’t be remedied merely by taking fish oil and other omega-3 supplements, rather get them from whole food sources, such as wild salmon, nuts, and vegetables, Yang said.
So, should people looking to ward off preventable diseases avoid a diet rich in sugars and opt for those with higher levels of omega-3 fatty acids, such as the Mediterranean diet?
“Definitely,” Yang said. “There’s a very strong linkage there.”