Washington: A new study has found that four weeks on a highly processed food diet leads to a strong inflammatory response in the brains of ageing rats that was accompanied by behavioural signs of memory loss. Researchers also found that supplementing the processed diet with the omega-3 fatty acid DHA prevented memory problems and almost entirely reduced inflammatory effects in older rats.
The research has been published in the journal Brain, Behaviour, and Immunity. Neuroinflammation and cognitive problems were not detected in young adult rats that ate the processed diet. The study diet mimicked ready-to-eat human foods that are often packaged for long shelf lives, such as potato chips and other snacks, frozen entrees like pasta dishes and pizzas, and deli meats containing preservatives.
Highly processed diets are also associated with obesity and type 2 diabetes, suggesting older consumers might want to scale back on convenience foods and add foods rich in DHA, such as salmon, to their diets, researchers say — especially considering harm to the aged brain in this study was evident in only four weeks.
The research team randomly assigned 3-month-old and 24-month-old male rats to their normal chow (32 per cent calories from protein, 54 per cent from wheat-based complex carbs and 14 per cent from fat), a highly-processed diet (19.6 per cent of calories from protein, 63.3 per cent from refined carbs - cornstarch, maltodextrin and sucrose - and 17.1 per cent from fat), or the same processed diet supplemented with DHA.
Activation of genes linked to a powerful pro-inflammatory protein and other markers of inflammation was significantly elevated in the hippocampus and amygdala of the older rats that ate the processed diet alone compared to young rats on any diet and aged rats that ate the DHA-supplemented processed food.
The older rats on the processed diet also showed signs of memory loss in behavioural experiments that weren't evident in the young rats. They forgot having spent time in an unfamiliar space within a few days, a sign of problems with contextual memory in the hippocampus and did not display anticipatory fear behaviour to a danger cue, which suggested there were abnormalities in the amygdala.
"The fact that we're seeing these effects so quickly is a little bit alarming," said senior study author Ruth Barrientos, an investigator in The Ohio State University Institute for Behavioural Medicine Research and associate professor of psychiatry and behavioural health.
"These findings indicate that consumption of a processed diet can produce significant and abrupt memory deficits — and in the ageing population, rapid memory decline has a greater likelihood of progressing into neurodegenerative diseases such as Alzheimer's disease.
By being aware of this, maybe we can limit processed foods in our diets and increase consumption of foods that are rich in the omega-3 fatty acid DHA to either prevent or slow that progression." Barrientos' lab studies how everyday life events — such as surgery, an infection or, in this case, an unhealthy diet — might trigger inflammation in the ageing brain.
