High-fat, high-sugar diets impact cognitive function

Published on Friday in the International Journal of Obesity, the research is the first to test in humans the relationship between HFHS diets, particularly those high in refined sugar and saturated fat, and first-person spatial navigation. Spatial navigation is the ability to learn and remember a path from one location to another, a process that can approximate the health of the brain’s hippocampus.

Dr Dominic Tran from the Faculty of Science’s School of Psychology led the research, which found HFHS diets have a detrimental effect on some aspects of cognitive function. It is likely those effects centre on the hippocampus, the brain structure important for spatial navigation and memory formation, rather than acting across the entire brain.

“The good news is we think this is an easily reversible situation,” Dr Tran said. “Dietary changes can improve the health of the hippocampus, and therefore our ability to navigate our environment, such as when we’re exploring a new city or learning a new route home.”

The research team recruited 55 university students aged between 18 and 38. Each participant completed questionnaires capturing their intake of sugary and fatty foods. They also had their working memory tested in a number recall exercise, and their body mass index (BMI) recorded.

The experiment itself required participants to navigate a virtual reality maze and locate a treasure chest six times. The maze was surrounded by landmarks that participants could use to remember their route. Their starting point and the location of the treasure chest remained constant in each trial.

If participants found the treasure in less than four minutes, they continued to the next trial. If they failed to find the treasure in this time, they were teleported to its location and given 10 seconds to familiarise themselves with that location before the next trial.

A seventh trial removed the treasure chest from the virtual maze but asked participants to find and mark its former location based purely on memory. Those with lower levels of fat and sugar in their diets were able to pinpoint the location with a higher degree of accuracy than those who consumed these foods multiple times a week.

“After controlling for working memory and BMI, measured separately to the experiment, participants’ sugar and fat intake was a reliable predictor of performance in that final, seventh, test,” Dr Tran said.

Dr Tran said the results highlight the importance of making good dietary choices to maintain healthy brain function.

“We’ve long known eating too much refined sugar and saturated fat brings the risk of obesity, metabolic and cardiovascular disease, and certain cancers. We also know these unhealthy eating habits hasten the onset of age-related cognitive decline in middle age and older adults.

“This research gives us evidence that diet is important for brain health in early adulthood, a period when cognitive function is usually intact,” Dr Tran said.

Dr Tran said the sample group used in this research was not representative of the wider population, but the findings still apply more broadly.

“It’s likely our participants were a little healthier than the general population and we think, if our sample better represented the public, the impact of diet on spatial navigation would likely be even more pronounced.”

Dr Tran is a recipient of an Australian Research Council Discovery Early Career Research Award (DECRA).