COLUMBUS, Ohio — There are plenty of waistline-related reasons to avoid highly processed foods, but a new study is adding yet another to the list. Ohio State University scientists report ultra-processed foods actively harm memory function within older brains.

Researchers fed a group of older rats a diet of highly processed foods for a month, sparking a strong inflammatory response in their brains. A number of behavioral signs of memory loss followed as well. Importantly, younger rats fed the same highly processed diet did not experience similar memory declines.

On a more positive note, study authors also found that providing the rodents with DHA (an omega-3 fatty acid) supplements prevented memory issues from occurring and eliminated the inflammatory effects almost entirely.

Which foods should you worry about eating?

The team used a specially crafted diet to re-create ready-to-eat human foods like potato chips, frozen foods, and deli meats containing preservatives.

“The fact we’re seeing these effects so quickly is a little bit alarming,” says senior study author Ruth Barrientos, an investigator in Ohio State’s Institute for Behavioral Medicine Research and associate professor of psychiatry and behavioral health, in a university release.

“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,” she continues.

A switch to fish can reduce inflammation

With previous studies linking a highly processed diet obesity, study authors say all older adults should do their best to avoid these products and opt for foods high in DHA, like salmon. DHA, short for docosahexaenoic acid, often comes in combination with eicosapentaenoic acid (EPA) in various fish and other seafoods. DHA helps serve multiple functions within the brain, but perhaps the most important is its role in fighting off inflammation. Still, this research is noteworthy as it is the first-ever to focus specifically on DHA’s ability to offset brain inflammation due to processed food.

Study authors assigned a collection of  three to 24-month-old male rats to one of three diets: “Normal” (32% calories from protein, 54% from wheat-based complex carbs and 14% from fat), highly processed (19.6% of calories from protein, 63.3% from refined carbs – cornstarch, maltodextrin and sucrose – and 17.1% from fat), and highly processed plus DHA supplements.

Older rats assigned to the highly processed diet showed gene activity linked to to a powerful pro-inflammatory protein. Moreover, these rats displayed other signs of inflammation within the hippocampus and amygdala. On a more actionable level, older rats eating a processed food diet also performed poorly and showed signs of memory loss during a series of tests. For example, the older rats appeared to forget about an area they had just spent some time in and failed to display anticipatory fear behavior to a danger cue. Both of these observations suggest abnormal activity and problems within the amygdala and hippcampus.

“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,” Prof. Barrientos adds.

Adding in some DHA supplements, however, appeared to do a great job of blocking any processed food-provoked inflammation and stopping potential memory loss.

Any processed foods lead to weight gain?

It’s worth mentioning that all rats eating processed foods ended up gaining significant weight, especially the older rodents. Even those also given DHA supplements saw no difference in this regard. The research team stresses that this work shouldn’t suggest that highly processed foods are OK as long as one also takes DHA supplements. The best option by far is to simply avoid such foods.

“These are the types of diets that are advertised as being low in fat, but they’re highly processed. They have no fiber and have refined carbohydrates that are also known as low-quality carbohydrates,” Prof. Barrientos concludes. “Folks who are used to looking at nutritional information need to pay attention to the fiber and quality of carbohydrates. This study really shows those things are important.”

The study appears in the journal Brain, Behavior, and Immunity.