Researchers at the University of New South Wales in Australia explored how a mostly healthy diet, when interspersed with unhealthy foods, affects brain function and gut health. The study, conducted under controlled laboratory conditions, investigated whether occasional indulgence in high-fat, high-sugar foods could shift cognitive performance and gut microbiota even when overall eating remained mostly nutritious.
Three experiments were carried out with laboratory mice. In each experiment, a control group of twelve mice fed a standard diet was compared with three other groups of twelve mice each. These groups received a processed diet rich in fats and sugars, with some mice consuming it consistently and others only intermittently. The design allowed researchers to observe both regular and cyclical exposure to an unhealthy dietary component against a baseline of normal feeding.
Memory and gut health were assessed at two key moments: before the dietary regimens began and after prescribed dieting periods. The researchers evaluated short-term memory through tasks that tested spatial awareness and the ability to remember the location of objects. Fecal samples were analyzed to determine the composition and diversity of gut microbiota, and body weight was recorded to monitor physical changes associated with diet.
Findings showed that mice who mostly ate healthy foods but occasionally consumed sugar- and fat-rich items displayed notable cognitive decline, particularly in tasks involving spatial memory. The same group also exhibited shifts in their gut microbial communities, with a reduction in overall diversity and a rise in species commonly linked to poorer gut health. These microbial changes were more pronounced as exposure to the unhealthy foods extended over longer periods.
As the duration of unhealthy eating increased, cognitive deficits tended to worsen. In later tests, mice in the intermittent- and longer-exposure groups struggled more with memory tasks requiring recall of object locations, indicating that even limited lapses into less nutritious choices could have lasting effects on brain function. The research highlights a connection between diet, gut microbiota, and cognitive performance that emerges more clearly with extended exposure.
The study’s authors emphasized the broader message: maintaining a balanced, nutritious diet is important for supporting both gut health and cognitive function over time, even when occasional indulgences occur. The results contribute to a growing body of evidence suggesting that diet can influence brain and gut health through changes in microbial communities and metabolic processes, underscoring the value of dietary consistency for long-term well-being.