Do You Have “Doughnut Brain”?
New research puts a spin on the urban legend that giving kids sugar causes hyperactive behavior. While the direct link between feeding kids sugar-rich treats and crazy behavior has largely been debunked, too much sugar is definitely not a good thing. Not for kids, and certainly not for older adults.
In fact, according to research conducted at Oregon State University, both high-fat and high-sugar diets cause changes in the gut bacteria of older adults, compared to a normal diet. And those changes have been linked to significant losses of “cognitive flexibility,” or the ability to adapt to changing circumstances. Sugar caused the most profound effects, even impairing learning due to deficits in short-term and long-term memory. Eating too many doughnuts—which are high in both sugar and fat—is an example of exactly the kind of thing that can impair one’s thinking.
"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. "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.”
Research on mice showed that a high-fat/high-sugar diet altered the makeup of the rodents’ gut bacteria, which in turn affected their ability to learn and think. "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.” With impaired cognitive flexibility, it’s less likely that you would adapt to this change in your routine, or remember the change in coming days.
"We've known for a while that too much fat and sugar are not good for you," Magnusson said. "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. It's not just the food that could be influencing your brain, but an interaction between the food and microbial changes."
K.R. Magnusson, L. Hauck, B.M. Jeffrey, V. Elias, A. Humphrey, R. Nath, A. Perrone, L.E. Bermudez. Relationships between diet-related changes in the gut microbiome and cognitive flexibility. Neuroscience, 2015; 300: 128 DOI: 10.1016/j.neuroscience.2015.05.016