How highly processed foods harm memory in the aging brain

(Ohio State News) - Four weeks on a diet of highly processed food led to a strong inflammatory response in the brains of aging rats that was accompanied by behavioral signs of memory loss, a new study has found.

Researchers also found that supplementing the processed diet with the omega-3 fatty acid DHA prevented memory problems and reduced the inflammatory effects almost entirely in older rats.

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 fact 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 Behavioral Medicine Research and associate professor of psychiatry and behavioral health.

“These findings indicate that consumption of a processed diet can produce significant and abrupt memory deficits – and in the aging 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.”

The research is published in the journal Brain, Behavior, and Immunity.

Barrientos’ lab studies how everyday life events – such as surgery, an infection or, in this case, an unhealthy diet – might trigger inflammation in the aging brain, with a specific focus on the hippocampus and amygdala regions. This work builds on her previous research suggesting a short-term, high-fat diet can lead to memory loss and brain inflammation in older animals, and that DHA levels are lower in the hippocampus and amygdala of the aged rat brain.

DHA, or docosahexaenoic acid, is an omega-3 fatty acid that is present along with eicosapentaenoic acid (EPA) in fish and other seafood. Among DHA’s multiple functions in the brain is a role in fending off an inflammatory response – this is the first study of its ability to act against brain inflammation brought on by a processed diet.

The research team randomly assigned 3-month-old and 24-month-old male rats to their normal chow (32% calories from protein, 54% from wheat-based complex carbs and 14% from fat), a highly processed diet (19.6% of calories from protein, 63.3% from refined carbs – cornstarch, maltodextrin and sucrose – and 17.1% 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.