A new study, published in the journal of Neuroscience, has revealed that a high fat and high sugar diet compared to a normal diet, causes changes in gut bacteria that affect the brain and the ability to adapt to changing situations.
This effect was most serious on the high-sugar diet, which revealed a clear impairment of early learning for both long-term and short-term memory.
The research study used mouse models for studies relevant to humans, and the mice consumed different diets and 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 in the human gut (microbiome) which consists of a complex mixture in the digestive system of about 100 trillion microorganisms.
“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.”
“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.”
The United States Western diet is particularly high in sugar, fat and simple carbohydrates and simple carbohydrates and has been linked to a range of chronic illnesses in the United States, including the obesity epidemic and an increased incidence of Alzheimer’s disease.
“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.”
Relationships between diet-related changes in the gut microbiome and cognitive flexibility, Kathy Magnusson et al., Neuroscience, doi:10.1016/j.neuroscience.2015.05.016, published online June 2015, abstract.