The study, published in the journal Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, found that eating more ultra-processed foods was associated with declines in attention and mental processing speed. Notably, the association held up even among people who otherwise followed a healthy diet ― a finding that experts say adds an important wrinkle to how we think about nutrition and brain health.
Researchers from Monash University, the University of São Paulo and Deakin University analyzed data from more than 2,100 middle-aged and older Australian adults, who underwent cognitive testing and filled out questionnaires about their food intake. Study participants consumed about 41% of their daily calories from ultra-processed foods, just shy of the Australian national average of 42%.
Ultra-processed foods include products like packaged cookies, soft drinks, frozen ready-made meals and other items that have undergone extensive industrial processing that goes far beyond basic cooking or preservation. Unlike fresh or minimally processed foods, they often contain additives, emulsifiers, artificial flavors and preservatives that you wouldn’t find in a home kitchen.
What scientists found is that for every 10% increase in ultra-processed food consumption ― roughly equivalent to adding a standard bag of chips to your daily diet ― there was a measurable decline in cognitive function and an increase in dementia risk factors.
It’s worth noting that the findings may not translate directly from Australia, where the study was conducted, to the United States. While Australians get about 42% of their daily calories from ultra-processed foods, the American average is 55%.
“I found the study compelling because it suggests that food processing itself may matter for brain health, not just the nutritional label,” Dr. Shaheen Lakhan, a neurologist who did not work on the study, told HuffPost. “What stood out most was that the association with attention persisted even among people who otherwise followed a Mediterranean-style diet.”
He believes we may need to look beyond categories like calories, fat, sugar and protein and pay attention to the effects of industrial processing on food and health as well.
“You can’t necessarily salad your way out of a heavily ultra-processed diet,” Lakhan said. “Healthy foods remain enormously important, but they may not completely offset the biological effects of highly processed products.”
Neuropsychologist Sanam Hafeez was similarly struck by the persistence of the association between ultra-processed foods and cognitive decline, even among people who generally ate well.
“That suggests food processing itself may have effects beyond simply lacking nutrients,” she noted. “I was also surprised by how relatively small increases in ultra-processed foods were linked to measurable differences in attention. Many people assume an occasional packaged snack is harmless, so these findings challenge that perception.”
There are multiple ways ultra-processed foods may harm the brain.
Experts say there are many different theories that may explain how ultra-processed foods can harm someone’s brain health.
“The brain is one of the most metabolically demanding organs in the body, so it is particularly vulnerable to chronic inflammation, vascular injury and metabolic dysfunction,” Lakhan explained. “Ultra-processed foods may contribute through several overlapping pathways. They are associated with obesity, hypertension, insulin resistance and cardiovascular disease, all of which are established risk factors for cognitive decline and dementia.”
“Beyond that, processing can alter the food matrix itself and introduce additives, emulsifiers and packaging-related chemicals that may affect the gut microbiome, inflammation and ultimately brain function,” he added.
Lakhan tells patients that the brain doesn’t simply consume nutrients but responds to biological signals, and that ultra-processed foods might send “the wrong signals repeatedly” over the years they’re eaten.
“High-temperature processing generates compounds known as advanced glycation end-products (AGEs), which have been implicated in damage to blood vessels and other tissues, including those of the nervous system,” noted Dr. Michael Stanley, a neurologist and assistant professor and Tufts University School of Medicine. “Certain chemicals, including bisphenol A, or BPA, can also migrate from plastic containers into food. Although the precise consequences remain under investigation, laboratory studies have raised concerns about their potential effects on neural tissue.”
He emphasized, however, that the full picture is cumulative rather than tied to a single mechanism.
“Diets rich in ultra-processed foods seem capable of sustaining a low-grade inflammatory state throughout the body,” Stanley said. “While less dramatic than the inflammation associated with infection or injury, this persistent background activity may, over time, contribute to neuronal damage and accelerate processes associated with aging of the brain.”
He also pointed to the role of vascular health in providing blood to the brain, which can be compromised by the high sodium content of ultra-processed foods. Meanwhile, lack of fiber and nutrients also contributes to less healthy blood flow and brain function.
There’s also an association between a diet high in ultra-processed foods and insulin resistance ― and the growing evidence that such metabolic disturbances can impact brain health and function.
“Finally, these foods may alter the ecology of the gut,” Stanley added. “The gastrointestinal tract houses a vast microbial community whose activities influence immune function, metabolism, and even aspects of cognition and mood. By disrupting this microbial balance, ultra-processed foods may affect the intricate dialogue that exists between the gut and the brain.”
Diet matters for brain health and for reducing dementia risk.
“Diet is one of the few dementia risk factors that people can meaningfully influence every single day,” Lakhan said. “We can’t change our genetics, but we can change what’s on our fork.”
This latest research adds to the increasingly long list of studies highlighting the relationship between diet and long-term brain health.
“My recommendation is simple: Eat foods that still resemble where they came from,” Lakhan said. “An olive should still look like an olive. A bean should still look like a bean. The further a food gets from its natural state, the more cautious I become.”
The experts who spoke to HuffPost pointed to the Mediterranean diet and the MIND diet as examples of whole food approaches linked to lower risk for Alzheimer’s and dementia.
“What’s good for the heart is good for the head,” Stanley said. “The Mediterranean diet focuses on eating lots of fruits, vegetables, whole grains, fish and olive oil, and has been shown to lower the risk of memory problems and dementia. The MIND diet takes this a step further by zeroing in on foods that are especially good for the brain ― particularly berries and green leafy vegetables like spinach and kale ― while also limiting red meat, fried foods, butter and sweets.”
Dr. Zaldy Tan, director of the Cedars-Sinai Health System Memory and Aging Program Neurology, noted that the new study actually reinforced the limits of even a healthy diet when ultra-processed food intake remains high.
“Diets that are rich in antioxidants, polyphenols, vitamins, minerals and healthy fats, like olive oil can decrease inflammation and be protective of the brain,” he said. “But even for people who have decent MIND diet scores, when they had high intakes of ultra-processed food, it still affected their attention.”
So even if you follow a generally healthy diet, it’s still not good for you to consume high amounts of ultra-processed foods. Eating healthy foods doesn’t simply cancel out all the unhealthy foods you had.
“For years, we’ve focused on what healthy foods to add. This study raises the possibility that what we remove may be just as important,” Lakhan noted. “Someone can have a salad for lunch and salmon for dinner, but if a substantial portion of their daily intake comes from ultra-processed foods, there may still be consequences. It’s a reminder that nutrition isn’t simply an accounting exercise where good foods cancel out bad ones. Biology is often more complicated than that.”
You can take these findings with you when you go to the supermarket.
“Stay on the outer aisles where it’s refrigerated because those are perishable items,” Tan said. “The ones in the center typically have very long shelf lives because they’re ultra-processed, with lots of preservatives, salt and sugar added. It’s important to tip the balance toward less processed foods rather than ultra-processed ones, and we’re all going to be better off in terms of our blood pressure, our sleep, our attention and long-term health.”
Of course, don’t get bogged down with guilt over every little food choice. It’s important to take a realistic approach to your diet backed by a healthy mindset.
“I encourage limiting highly processed foods rather than focusing on perfection,” Hafeez said. “I also think it’s important not to jump to conclusions from one study. There could be other factors involved that we do not fully understand. I think the finding raises some interesting questions about how diet affects the brain.”
She emphasized that the study shows a relationship between ultra-processed foods and cognitive decline, rather than proving cause and effect.
“This information is suggestive of an association, not necessarily causation,” Tan echoed. “It doesn’t mean that consuming ultra-processed foods is necessarily the cause of the findings because it could be that consumption of ultra-processed food is also tied to other unhealthy behaviors. And these types of studies are observational and based on food recall with frequency questionnaires, so there could be some inherent recall bias. So we have to take this information with a grain of salt.”
The study’s focus on attention is notable.
Experts say the study’s focus on attention, rather than memory, is significant.
“Attention is the brain’s gateway function,” Lakhan said. “If attention falters, memory, learning, decision-making and problem-solving often suffer downstream. A useful analogy is that memory gets most of the headlines, but attention is often the operating system running in the background.”
You can have an excellent memory, but if you aren’t able to pay attention, then you won’t take in the information you need to remember.
“Attention varies more from a day-to-day standpoint than memory does,” Tan said. “It can be affected acutely by, say, a rise in blood sugar ― you get that sugar rush and then crash. Memory doesn’t get affected as quickly. Also the participants were relatively young, so you don’t expect their memory to be significantly affected yet. But attention may be affected even in young people.”
So when should declining attention be a cause for concern? Experts say context matters.
“Occasional lapses in attention are normal and happen to everyone. Stress, poor sleep, anxiety and even multitasking can affect focus,” Hafeez said. “However, persistent changes in attention can sometimes signal a deeper issue. People should pay attention to whether concentration problems are becoming more frequent or interfering with daily life. Forgetting important information, struggling to follow conversations, or having difficulty completing familiar tasks are worth noting.”
While these symptoms don’t automatically mean you have dementia, you shouldn’t ignore them either. Be mindful of changes that family members and friends notice as well.
“Attention difficulties can sometimes precede more obvious cognitive symptoms,” Lakhan said. “People should pay attention to persistent changes such as increased distractibility, difficulty following conversations, trouble completing familiar tasks or needing substantially more effort to stay focused than before.”
Stanley recommended tracking patterns over time.
“People should pay attention to trends in chronicity, frequency, severity, and nature of their attentional problems to better characterize it and identify any triggers,” he said. “When in doubt, always ask your doctor.”
Otherwise, you can focus on general lifestyle factors like sleep, exercise, diet and social time. The study findings point to the importance of good health-promoting habits.
“The less food is engineered in a factory, the more likely it is to support the organ that makes us who we are,” Lakhan said.
He emphasized that what’s convenient for the food industry is not always convenient for our brains. And while we might sometimes have to make less healthy choices, that doesn’t change the overall goal.
“The biggest takeaway is that brain health is built meal by meal, year by year, often long before symptoms appear,” Lakhan said. “This study doesn’t mean that eating a bag of chips will cause dementia. What it suggests is that small, repeated dietary choices may accumulate over decades and influence how our brains age.”