Ultra-processed foods have already been tied to a long list of health concerns, from heart disease to type 2 diabetes. Now new research suggests that these so-called convenience foods could contribute to changes that negatively affect brain health.
Even small differences mattered, they discovered: For every 10 percent increase in ultra-processed foods eaten, participants had a small but measurable drop in attention scores.
“To put our findings in perspective, a 10 percent increase in ultra-processed foods is roughly equivalent to adding a standard packet of chips to your daily diet,” says lead author Barbara Cardoso, PhD, a researcher in the department of nutrition, dietetics, and food at Monash University’s Victorian Heart Institute in Australia.
Diets Higher in Ultra-Processed Foods Linked to Shorter Attention Spans
The study included more than 2,000 adults ages 40 to 70 who were part of the Healthy Brain Project. None had dementia, though many had a family history of it.
Participants filled out a detailed food questionnaire about what they typically ate over the previous year; researchers used a standardized tool to estimate how processed those foods were.
Subjects also completed online cognitive tests that measured attention, processing speed, and memory.
Using all of this data, the investigators estimated dementia risk using a tool that includes factors such as age, education, sex, cholesterol, blood pressure, physical activity, and body weight. Researchers also utilized a version of that score focused on modifiable dementia risk factors, meaning those that a person can change or manage.
Researchers found that adults who ate the most ultra-processed foods had the lowest attention scores, compared with people who ate the least.
Diets higher in ultra-processed foods were also linked to having more modifiable dementia risk factors, including high blood pressure, high cholesterol, low physical activity, and obesity.
Importantly, the data didn’t show a significant association between ultra-processed food intake and memory scores.
Study Adds to a Growing Body of Research on Diet, Cognitive Impairment, and Dementia
Benjamin Katz, PhD, an associate professor of human development and family science at Virginia Tech in Blacksburg, points out that the overall effect of ultra-processed food on attention was relatively small.
However, the effect on modifiable dementia risk factors was much more robust, says Dr. Katz, who researches the health effects of ultra-processed foods but wasn’t involved in the new study.
“This study adds to the growing evidence that higher consumption of ultra-processed foods is associated with a higher risk of cognitive impairment and dementia,” says W. Taylor Kimberly, MD, PhD, a critical care neurologist, researcher, and associate professor of neurology at Harvard Medical School in Boston, who wasn’t involved in the investigation.
These findings confirm other research in different groups of people around the world, says Dr. Kimberly.
“It also shows that higher ultra-processed foods consumption is linked to subtler signs of impairment in cognitive performance,” he says, adding that the findings should “serve as a growing indicator that ultra-processed foods are linked to several aspects of brain health, which collectively can inform individuals, nutritionists, physicians, and policymakers.”
How Ultra-Processed Foods May Impact the Brain
Ultra-processed foods are packaged or industrially made products that often contain ingredients not typically used in home cooking, such as artificial colors, flavors, preservatives, emulsifiers, sweeteners, and other food additives.
Examples include soft drinks, packaged salty snacks, sweets, instant soups, deli meats, packaged breads, dairy-based desserts and drinks, ready-made meals, and some breakfast cereals. Some estimates suggest that these foods and drinks comprise up to 70 percent of the average American diet.
Processed foods are known to disrupt the gut microbiome, the collective term for the bacteria, fungi, and other organisms that aid digestion and help maintain the immune system. Because the gut and brain communicate with each other, changes in the gut may be one way that diet influences brain health, the authors wrote.
These foods could also impact the endocrine system, which controls hormones, and contribute to negative neurological outcomes, says Dr. Cardoso.
Even People Who Followed a Mostly Healthy Diet Were Affected by Eating Ultra-Processed Foods
One of the key questions was whether ultra-processed foods were linked to worse attention simply because people who ate more of them were eating fewer healthy foods.
To test that, researchers adjusted for Mediterranean diet adherence, a commonly used measure of overall diet quality.
Still, the link between ultra-processed foods and poorer attention remained.
That suggests that the association is not explained only by what the ultra-processed foods may replace, such as fruits, vegetables, whole grains, beans, nuts, fish, and other foods often associated with brain health, the authors wrote.
You can eat a mostly Mediterranean-style diet but still consume specific foods that might be problematic, says Katz.
“In our work we’ve found that ultra-processed animal products (think off-the-shelf deli meat) and sugar-sweetened beverages are particularly associated with increased risk for cognitive impairment,” he says.
Limitations and Questions About the Definition of Ultra-Processed Foods
The study has important limits. Because of its design, researchers could only measure diet and cognitive function at a single moment in time. That means the results can’t prove whether ultra-processed foods caused worse attention or whether other factors were involved — they can only show a link.
The research also required subjects to self-report their diet, as is the norm in many studies like this, which introduces the possibility for reporting error. In addition, the questionnaire wasn’t designed specifically to measure ultra-processed foods. The participants were mostly women, many had higher education and socioeconomic status, and many had a family history of dementia, which may limit how the findings might apply to a larger population.
Another issue is that “ultra-processed foods” can be a big category that lumps together very different foods, from sugary drinks and refined snacks to whole-grain cereals, fortified foods, and flavored yogurt, says Steven K. Clinton, MD, PhD, professor of internal medicine at The Ohio State University Comprehensive Cancer Center in Columbus, who wasn’t involved in the new study.
Sorting foods according to the number of ingredients and the technology used to make the foods — but not the actual nutritional value — could just end up confusing people and distracting from the larger issue.
Rather than focusing on processing level, Dr. Clinton tells his patients to focus on a healthy diet based on the Dietary Guidelines for Americans and American Heart Association dietary guidelines.
When it comes to brain health, he recommends a diverse array of fruits and vegetables, healthy fats including omega-3s, and high-fiber foods.
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