What ultra processed foods can do to the brain
Roughly 60% of the calories in the average American diet come from highly processed foods. We’ve known for decades that eating such packaged products — like some breakfast cereals, snack bars, frozen meals and virtually all packaged sweets, among many other things — is linked to unwelcome health outcomes, like an increased risk of diabetes, obesity and even cancer. But more recent studies point to another major downside to these often delicious, always convenient foods: They appear to have a significant effect on our minds, too.
Research from the past 10 or so years has shown that the more ultraprocessed foods a person eats, the higher the chances that they feel depressed and anxious. A few studies have suggested a link between eating UPFS and increased risk of cognitive decline.
What’s so insidious about these foods, and how can you avoid the mental fallout? Scientists are still working on answers, but here’s what we know so far.
Which items qualify?
In 2009, Brazilian researchers put food on a four- part scale, from unprocessed and minimally processed ( like fruits, vegetables, rice and flour) to processed ( oils, butter, sugar, dairy products, some canned foods, and smoked meats and fish) and ultraprocessed. “Ultraprocessed foods include ingredients that are rarely used in homemade recipes — such as high- fructose corn syrup, hydrogenated oils, protein isolates and chemical additives” like colors, artificial flavors, sweeteners, emulsifiers and preservatives, said Eurídice Martínez Steele, a researcher in food processing at University of Sao Paulo in Brazil. This classification system is now used widely by nutrition researchers.
UPFS make up a majority of the packaged foods you find in the frozen food aisles at grocery stores and on the menu at fastfood restaurants — 70% of the packaged foods sold in the United States are considered ultraprocessed. They’re increasingly edging out healthier foods in people’s diets and are widely consumed across socioeconomic groups.
“Ultraprocessed foods are carefully formulated to be so palatable and satisfying that they’re almost addictive,” said Dr. Eric M. Hecht, a public health researcher at the Schmidt College of Medicine at Florida Atlantic University. “The problem is that in order to make the products taste better and better, manufacturers make them less and less like real food.”
The effect on mental health
Recent research has demonstrated a link between highly processed foods and low mood. In one 2022 study of over 10,000 adults in the United States, the more UPFS participants ate, the more likely they were to report mild depression or feelings of anxiety. “There was a significant increase in mentally unhealthy days for those eating 60% or more of their calories from UPFS,” Hecht, the study’s author, said. “This is not proof of causation, but we can say that there seems to be an association.”
New research has also found a connection between high UPF consumption and cognitive decline. A 2022 study that followed nearly 11,000 Brazilian adults over a decade found a correlation between eating ultraprocessed foods and worse cognitive function ( the ability to learn, remember, reason and solve problems). “While we have a natural decline in these abilities with age, we saw that this decline accelerated by 28% in people who consume more than 20% of their calories from UPFS,” said Natalia Gomes Goncalves, a professor at the University of São Paulo Medical School and the lead author of the study.
It’s possible that eating a healthy diet may offset the detrimental effects of eating ultraprocessed foods. The Brazilian researchers found that following a healthy eating regimen, like the MIND diet — rich in whole grains, green leafy vegetables, legumes, nuts, berries, fish, chicken and olive oil — greatly reduced the dementia risk associated with consuming ultraprocessed foods. Those who followed the MIND diet but still ate UPFS “had no association between UPF consumption and cognitive decline,” Goncalves said, adding that researchers still don’t know what a safe quantity of UPFS is.
It’s unclear why ultraprocessed foods might have this effect. “Many high- quality, randomized studies have shown the beneficial effect of a nutrientdense diet on depression, but we still do not fully understand the role of food processing on mental health,” said Melissa Lane, a researcher at the Food & Mood Centre at Deakin University in Australia. However, there are some clues.
Much of the research has focused on how poor gut health might affect the brain. Diets that are high in ultraprocessed foods are typically low in fiber, which is mostly found in plantbased foods like whole grains, fruits, vegetables, nuts and seeds. Fiber helps feed the good bacteria in the gut. Fiber is also necessary for the production of short- chain fatty acids, the substances produced when it breaks down in the digestive system, and which play an important role in brain function.