There has been a lot of press recently about the microbiome’s impact on mood and behavior, the so-called ‘gut-brain axis’, and it appears now more than ever that the gut microbiome has a substantial impact on the brain. A new paper out of Oregon State University, published in the journal Neuroscience, furthers this research by showing that different diets affect mice’s cognition and memory via changes in the microbiome.

Scientists fed groups of mice a normal chow and then switched their food to either high fat, or high diets, along with continuing some on the normal diet. The researchers then put them through a battery of cognitive tests, all the while measuring their microbiomes using stool samples. The mice on the high sucrose and high fat diets each had similar alterations of their microbiomes, such as an increase in Clostridiales and a decrease in Bacteroidales. Mice on the high sucrose diet had decreased scores in their cognition tests, including memory and spatial reasoning tests, which corresponded to changes in the microbiome. For example, an increase in Lactobacilli was associated with a decrease in spatial reasoning. Mice on the high fat diet, on the other hand, showed impaired working memory, which was associated with an increase in bacteroidales.

Some of these bacteria, such as Lactobacillus are used in probiotics to increase cognitive function, and there is some scientific basis for these effects, even though this study observes a somewhat different results. The changes in this study though, were a diet intervention, which is more complex than a simple probiotic intervention. That being said, we must remember that microbiome science is still developing, so each of these studies should be considered in the broader context of the field before any real conclusions can be made.