A new animal study from Oregon State University indicates that both a high-fat and a high-sugar diet, compared to a normal diet, cause changes in gut bacteria that appear related to a significant loss of 'cognitive flexibility,' or the power to adapt and adjust to changing situations. This effect was most serious on the high-sugar diet, which also showed an impairment of early learning for both long-term and short-term memory.
The findings are consistent with some other studies about the impact of fat and sugar on cognitive function and behavior, 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 laboratory 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.
It's increasingly clear that our gut bacteria, or microbiota, can communicate with the human brain. Bacteria can release compounds that act as neurotransmitters, stimulate sensory nerves or the immune system, and affect a wide range of biological functions.
Researchers note mice have proven to be a particularly good model for studies relevant to humans on such topics as aging, spatial memory, obesity and other issues.
In the new study, 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 decline, 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," the lead researcher 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.
This study was done with young animals, which ordinarily would have a healthier biological system that's better able to resist pathological influences from their microbiota. The findings might be even more pronounced with older animals or humans with compromised intestinal systems, the researchers said.
These new findings suggest that fat and sugar alter healthy gut bacteria; it's not just the food that may influence your brain, but an interaction between the food and microbial changes.
Source: Neuroscience, 2015.
All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.