A range of diseases — from diabetes to cardiovascular disease, and from Alzheimer’s disease to attention deficit hyperactivity disorder — are linked to changes to genes in the brain. A new study by UCLA life scientists has found that hundreds of those genes can be damaged by fructose, a sugar that’s common in the Western diet, in a way that could lead to those diseases.
However, the researchers discovered good news as well: 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.”
DHA occurs naturally in the membranes of our brain cells, but not in a large enough quantity to help fight diseases.
“The brain and the body are deficient in the machinery to make DHA; it has to come through our diet,” said Fernando Gomez-Pinilla, a UCLA professor of neurosurgery and of integrative biology and physiology, and co-senior author of the paper.
DHA strengthens synapses in the brain and enhances learning and memory. It 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, said Gomez-Pinilla, who also is a member of UCLA’s Brain Injury Research Center.
Americans get most of their fructose in foods that are sweetened with high-fructose corn syrup, an inexpensive liquid sweetener made from corn starch, and from sweetened drinks, syrups, honey and desserts. The Department of Agriculture estimates that Americans consumed an average of about 27 pounds of high-fructose corn syrup in 2014. Fructose is also found is in most baby food and in fruit, although the fiber in fruit substantially slows the body’s absorption of the sugar — and fruit contains other healthy components that protect the brain and body, Yang said.
To test the effects of fructose and DHA, the researchers 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.