A study from Oregon State University shows that a high-fat, high-sugar diet results in a significant loss of 'cognitive flexibility' or the power to adapt to change.
The findings are consistent with some other studies about the impact of fat and sugar on cognitive function and behaviour, and suggest that some of these problems may be linked to alteration of the microbiome – a complex mixture in the digestive system of about 100 trillion microorganisms.
The research was done with mice that consumed different diets and then faced a variety of tests, such as water maze testing, to monitor changes in their mental and physical function, and associated impacts on various types of bacteria. The findings were published in the journal Neuroscience.
“It’s increasingly clear that our gut bacteria, or microbiota, can communicate with the human brain,” said principal investigator Kathy Magnusson. “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.”
Mice have proven to be a particularly good model for studies relevant to humans, Magnusson said, on such topics as ageing, spatial memory, obesity and other issues. In this research, after just four weeks on a high-fat or a high-sugar diet, the performance of mice on various tests of mental and physical function began to drop, compared to animals on a normal diet. One of the most pronounced changes was in what researchers call cognitive flexibility.
“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. A person with high levels of cognitive flexibility would immediately adapt to the change, determine the next best route home, and remember to use the same route the following morning, all with little problem. With impaired flexibility, it might be a long, slow, and stressful way home."