Junk food is not only bad for your health, it can also make you stupid.
That’s the conclusion of a research team from the University of New South Wales studying the effects of a high sugar and high fat diet on memory in rats.
The research found that after just six days, the rats began to suffer cognitive impairment.
But don’t take a sigh of relief if you’re drinking a Coke with your salad. The results were similarly poor for rats fed a healthy diet, but given sugar water to drink.
Professor Margaret Morris, from the UNSW School of Medical Sciences, a co-author of the study, said the rats had inflammation of the brain’s hippocampal region, which is associated with spatial memory as well as demonstrating a reduced ability to notice when an object had been moved to a new location.
The rats were tested at five, 11 and 20 days of the diet and problems with memory appeared even before the animals began to gain weight from the diet.
Some aspects of the animals’ memories were spared, regardless of their diets. All the animals were equally able to recognise objects after eating either the “healthy”, “cafeteria” (high in fat and sugar, including cake, chips and biscuits) or “healthy with sugar” regimes.
Professor Morris said the surprise was the speed at which the deterioration occurred.
“We know that obesity causes inflammation in the body, but we didn’t realise until recently that it also causes changes in the brain. Our preliminary data also suggests that the damage is not reversed when the rats are switched back to a healthy diet, which is very concerning,” she said.
Anyone who saw the 2004 documentary Super Size Me, in which Morgan Spurlock ate nothing but McDonalds for 30 days and began to suffer from depression already suspects that diet affects behaviour, and Professor Morris believes the findings of this study will have relevance to human diets.
“While nutrition affects the brain at every age, it is critical as we get older and may be important in preventing cognitive decline. An elderly person with poor diet may be more likely to have problems.”
There’s also an implication that the foods themselves dumb you down enough to make you keep eating them.
“Given that high energy foods can impair the function of the hippocampus, if you eat a lot of them it may contribute to weight gain, by interfering with your episodic memory,” says Professor Morris.
“People might be less aware of their internal cues like hunger pangs and knowing when they have had enough.”
Ongoing work will attempt to establish how to stop the inflammation in the brain of animals with the unhealthy diets.
The study was funded by the National Health and Medical Research Council and published today in the journal Brain, Behaviour and Immunity.
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