Highly processed food can harm memory in the aging brain

Study in animals suggests omega-3 supplement may reduce effects.


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A highly processed diet is enriched with refined carbohydrates, saturated fats and lacks fiber. Previous studies have suggested that this diet negatively impacts brain health and cognitive function. However, mechanisms by which PD affects the aged brain are unknown.

To fill this knowledge gap, scientists at the Ohio State University conducted a study on aging rats. They found that highly processed food led to a strong inflammatory response in the brains of aging rats that was accompanied by behavioral signs of memory loss.

Scientists fed rats with ready-to-eat human foods 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.

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, said“The fact we see these effects so quickly is a little bit alarming. 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.”

However, scientists didn’t detect neuroinflammation and cognitive problems in young rats who ate processed diets.

Eating highly processed food is also linked to obesity, type 2 diabetes. This suggests older consumers avoid such food and switch to foods rich in DHA, such as salmon.

DHA, or docosahexaenoic acid, is an omega-3 fatty acid 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 study involved 3-month-old and 24-month-old male rats. Scientists feed them 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.

Older rats who ate processed food showed signs of memory loss in behavioral experiments. The signs were not evident in young rats.

Older rats 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 behavior to a danger cue, which suggested abnormalities in the amygdala.

When the rats consumed DHA supplementing of processed food, this effectively prevented the elevated inflammatory response in the brain and signs of memory loss.

Journal Reference:
  1. Michael J.Butler, Ruth M.Barrientos et al. Dietary DHA prevents cognitive impairment and inflammatory gene expression in aged male rats fed a diet enriched with refined carbohydrates. DOI: 10.1016/j.bbi.2021.08.214


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