Processed Foods Linked to Emotional Memory Issues in Aged Brains

Study finds lack of fiber, not just fat or sugar, may be a key culprit behind cognitive problems in older adults

Published on Feb. 27, 2026

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A new study suggests that a lack of fiber in highly processed diets, rather than just high fat or sugar, may be a key factor behind cognitive problems and emotional memory issues in the aged brain. The research in rats found that all refined diets, regardless of fat or sugar content, were linked to cellular and behavioral signs of impaired memory function in the amygdala, the brain region governing emotional memories. The common thread across the diets was a lack of fiber, which is needed to produce butyrate, a molecule with anti-inflammatory effects that can cross the blood-brain barrier.

Why it matters

The findings are concerning for older adults who may be at greater risk of financial exploitation and scams, as the amygdala plays a key role in learning to associate actions with their outcomes, especially dangerous or risky ones. The vulnerability of the amygdala to refined diets lacking in fiber could impair this type of emotional learning and awareness in aging populations.

The details

The study exposed young and aged male rats to either normal chow or one of five experimental diets for three days: low fat/low sugar, low fat/high sugar, medium fat/low sugar, medium fat/high sugar, or high fat/low sugar. Behavioral tests showed that older rats on all the refined diets had impaired long-term emotional memory tied to the amygdala, compared to young rats on the same diets. In contrast, memory linked to the hippocampus was only negatively affected by the high-fat, low-sugar diet. Examination of the rats' guts and blood revealed a significant reduction in butyrate, a molecule produced when gut microbes break down dietary fiber, across the refined diets.

  • The study was recently published in the journal Brain, Behavior, and Immunity.

The players

Ruth Barrientos

An investigator in the Institute of Brain, Behavior and Immunology at The Ohio State University, as well as an associate professor of psychiatry and behavioral health and neuroscience in Ohio State's College of Medicine.

Kedryn Baskin

Assistant professor of physiology and cell biology at Ohio State.

The Ohio State University

The institution where the research was conducted.

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What they’re saying

“The amygdala is important for learning the association between something fearful and a bad outcome. And we found that all of the refined diets, whether they were high fat, high sugar, low fat, low sugar, it didn't matter. They all impaired memory that's governed by the amygdala.”

— Ruth Barrientos, Investigator, Institute of Brain, Behavior and Immunology (Mirage News)

“What our study really brings to light is the complexity of diet and how it affects so many different things, even the brain. There's not a magic bullet, but in this case, low butyrate, as a result of a lack of fiber, is a culprit.”

— Kedryn Baskin, Assistant Professor, Physiology and Cell Biology (Mirage News)

What’s next

The research team plans to study whether fiber or butyrate supplementation in animals could reverse the age-related cognitive problems that follow poor eating.

The takeaway

This study highlights the complex relationship between diet, gut health, and brain function, particularly in older adults. The findings suggest that increasing fiber intake may be an important dietary strategy to help maintain emotional memory and cognitive function as we age.