Diet enriched with highly processed food leads to a strong inflammatory response in the brain which signals memory loss, according to a new study conducted on aging rats.
Researchers also found that replacing processed foods with omega-3 fatty acid DHA reduced the inflammatory effects and prevented memory problems in older rats. However, no such cognitive issues were found in young rats that were given a processed food-enriched diet. The research has been published in the journal ‘Brain, Behavior, and Immunity’.
The diet for the study 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.
“The fact we’re seeing these effects so quickly is a little bit alarming,” said senior study author Ms. Ruth Barrientos, an investigator in The Ohio State University Institute for Behavioral Medicine Research and associate professor of psychiatry and behavioral health.
The results from the study signal 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 like Alzheimer’s disease.
Increasing the consumption of foods that are rich in omega-3 fatty acid DHA will help either prevent or slow that progression. Docosahexaenoic acid (DHA) 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, it has a role in fending off an inflammatory response.
The research team randomly assigned 3-month-old and 24-month-old male rats to their normal chow (32 percent calories from protein, 54 percent from wheat-based complex carbs and 14 percent from fat), a highly-processed diet (19.6 percent of calories from protein, 63.3 percent from refined carbs, cornstarch, maltodextrin and sucrose, and 17.1 percent 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 behavioral 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 behavior to a danger cue, which suggested there were abnormalities in the amygdala.
“The amygdala in humans has been implicated in memories associated with emotional-fear and anxiety-producing events. If this region of the brain is dysfunctional, cues that predict danger may be missed and could lead to bad decisions,” Ms. Barrientos said.
Researchers don’t know the exact dosage of DHA or precise calories and nutrients, taken in by the animals, which all had unlimited access to food. Both age groups gained a significant amount of weight on the processed diet, with old animals gaining significantly more than the young animals. DHA supplementation had no preventive effect on weight gain associated with eating highly processed foods.
Ms. Barrientos cautioned against interpreting the results as a license for consumers to feast on processed foods as long as they take a DHA supplement. A better bet to limit multiple negative effects of highly refined foods would be focusing on overall diet improvement.