Excess fat and sugar can harm brain function: Study

Waistlines, cholesterol and blood sugar levels are well-known casualties of a diet high in sugar and fat, leading to health problems such as obesity, cardiovascular disease and some types of cancer.
 
Now, a world-first study from the University of Sydney has added to the growing body of evidence of the impact of such foods on a person’s cognitive function.
 
Chair of RACGP Specific Interests Obesity Management, GP and dietitian, Dr Terri-Lynne South, said it was important for GPs to bear in mind that the typical Australian diet is high in refined sugars and saturated fat, which is ‘concerning’.
 
‘What I took out of this research is that we really need to be talking to our patients about healthy lifestyles and healthy eating for a number of health reasons,’ Dr South told newsGP.
 
The research, published in The International Journal of Obesity, is the first to test in humans the impact of a high-fat, high-sugar diet on spatial navigation, which is the ability to learn and remember a path from one location to another.
 
Lead researcher Dr Dominic Tran, from the university’s School of Psychology, said spatial navigation can be used to estimate the health of the brain’s hippocampus, the part of the brain essential for the process.
 
Dr Tran said the hippocampus was also the part of the brain thought to most likely be affected by a high-fat, high-sugar diet.
 
Experimental studies using rodents have already shown that diets high in fats and sugars can impair brain functions, particularly in the hippocampus.
 
The good news, however, is that the effects of a high-sugar, high-fat diet on a person’s cognitive function are ‘easily reversible’, said Dr Tran.
 
‘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,’ he said.
 
The University of Sydney study involved 55 participants aged between 18 and 38. Each person recorded their intake of sugary and fatty foods, had their working memory tested in a number recall exercise, and their body mass index (BMI) recorded.
 
They then had to navigate a virtual reality maze and locate a treasure chest six times, using landmarks to remember their route.
 
A seventh trial removed the treasure chest from the virtual maze, but asked participants to find its former location based purely on memory.
 
Those with lower levels of fat and sugar in their diets were able to pinpoint the location more accurately than those who consumed these foods several times a week.
 
After taking into account the participants’ previously recorded working memory and BMI results, their sugar and fat intake became ‘a reliable predictor of performance’ in the seventh test, Dr Tran said.
 
Although the study’s participants were aged between 18 and 38 years, he said the findings could be applied to the broader population – and would likely show an even greater impact.
 
‘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 said.
 
The results also highlight the importance of a healthy diet to maintain healthy brain function.
 
‘We’ve long known … these unhealthy eating habits hasten the onset of age-related cognitive decline in middle age and older adults,’ Dr Tran said.
 
‘This research gives us evidence that diet is important for brain health in early adulthood, a period when cognitive function is usually intact.’
 
Dr South said while questions about a patient’s diet are not ‘necessarily’ part of a standard consultation, she believes they could be.
 
‘It can just be a couple of simple questions that GPs can ask,’ she said.
 
‘One is, “what’s your relationship like with food?”, to get a sense of how they feel about their eating. The other is to just take a very simple diet history.’
 
Dr South said the research findings reinforce the importance of a healthy diet and lifestyle.
 
‘It just goes to show that, from an eating point of view, healthy lifestyle is so important, in ways we’re only just finding out,’ she said.
 
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brain function cognitive function healthy diet high fat high sugar hippocampus research spatial navigation