CORVALLIS, Ore., June 23 (UPI) -- A diet high in both fat and sugar can cause changes in a person's microbiome, or the trillions of bacteria that live inside the body and help it function, which may affect cognitive flexibility, or the ability to change and adapt to the world around you, according to a study at Oregon State University.
Researchers say the study's results are another indictment of the "Western diet," which is often high in sugar, fat and simple carbohydrates and has been linked to the obesity epidemic.
"It's increasingly clear that our gut bacteria, or microbiota, can communicate with the human brain," said Kathy Magnusson, a professor in the OSU College of Veterinary Medicine and principal investigator with the Linus Pauling Institute, in a press release. "Bacteria can release compounds that act as neurotransmitters, stimulate sensory nerves or the immune system, and affect a wide range of biological functions," she said. "We're not sure just what messages are being sent, but we are tracking down the pathways and the effects."
For the study, mice were fed several different diets and then put through tests of their cognitive function, such as water maze testing. After four weeks of a diet high in fat or sugar, the performance of the mice dropped in tests, especially on those that required them to react to changes in their situation or surroundings.
"The impairment of cognitive flexibility in this study was pretty strong," Magnusson said. "Think about driving home on a route that's very familiar to you, something you're used to doing. Then one day that road is closed and you suddenly have to find a new way home."
Magnusson said that while researchers have been aware for some time that too much sugar or fat can negatively affect the body, research about the overall "Western diet" is beginning to show effects beyond the belt. "This work suggests that fat and sugar are altering your healthy bacterial systems, and that's one of the reasons those foods aren't good for you," she said.
The study is published in Neuroscience.