Oregon State University researchers have discovered a new link between cognitive functioning and gut bacteria.  In recent years the science involving bacteria in the gut and its link to health and cognitive functioning has boomed.  Parkinson’s disease has even been linked to changes in gut bacteria.  Published in the journal Neuroscience, a new study shows that diets high in fat and sugar are probably impacting cognitive functioning, because of their impact on the type of bacteria that thrive on high-fat and high-sugar diets.  

These diets, according to Professor Kathy Magnusson of OSU’s Linus Pauling Institute, trigger changes in gut bacteria that seem to be associated with a noticeable loss of ability to adapt to situations when they veer off course, a skill called “cognitive flexibility.”

Medical News Today explained cognitive flexibility with an example provided by Prof. Magnusson.

“Explaining what cognitive flexibility is, Prof. Magnusson asks us to imagine driving home using a route that is very familiar. One day, the road is closed, meaning we need to find a different route.

“An individual with a high level of cognitive flexibility would adapt to the situation straight away, immediately seeking out an alternative route. But a person with impaired cognitive flexibility may find the unexpected change in situation very stressful, causing them to become flustered and take longer getting home.”

Diets high in sugar and high in fat, which are common in the Western diet, seem to also cause poor memory. Both long-term and short-term memory may suffer when people eat food typically found in a fast food meal, or the average American elementary school child’s lunch. Prof. Magnusson said that the body of evidence that has been gathering since scientists began looking at the link between gut bacteria and the brain is that gut bacteria has a direct line of communication with the brain.

“Bacteria can release compounds that act as neurotransmitters, stimulate sensory nerves or the immune system, and affect a wide range of biological functions. We’re not sure just what messages are being sent, but we are tracking down the pathways and the effects.”

In the research study, the test subjects, which were young male mice, were randomly fed high-fat diets (42 percent fat), high-sugar diets (70 percent carbohydrate), or their normal diets. The test window was two weeks long. The fecal bacterium of the mice were sampled before and after the two-week period. The subjects’ cognitive functioning was also assessed before and after the two-week long diet test.

Both the high-fat and the high-sugar diets were found to increase bacteria known as Clostridiales. These diets also reduced bacteria known as Bacteroidales, but the sugar-fed subjects had the highest growth of Clostridiales and the biggest decline of Bacteroidales. The test subjects fed the high-sugar diets also suffered the greatest decline in cognitive functioning.

“We’ve known for a while that too much fat and sugar are not good for you. 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,” Prof. Magnusson said. “It’s not just the food that could be influencing your brain, but an interaction between the food and microbial changes.”

“It’s increasingly clear that our gut bacteria, or microbiota, can communicate with the human brain,” said Kathy Magnusson of the link between changes in gut bacteria and changes in cognitive flexibility and memory.

Image credit:  Umberto Salvagnin | Flickr