A large new study shows that diets high in ultra-processed foods are linked to an increased risk of stroke and cognitive decline in adults. This risk exists regardless of the overall quality of the diet, according to research published in the journal Neurology. The study analyzed data from over 30,000 adults in the United States, suggesting that food processing itself may affect brain health beyond traditional nutrition factors.
Ultra-processed foods make up most of the calories consumed in the U.S. These foods contain ingredients rarely used in home cooking, such as emulsifiers, artificial flavors, and stabilizers. They are designed to be highly tasty and convenient. Examples include packaged snacks, sugary drinks, processed meats, and ready-made meals.
Previous research has linked eating a lot of ultra-processed foods to problems like obesity, high blood pressure, and heart disease. Some studies hinted at a connection to worse brain health, but it was unclear if this was due to poor overall diet or the processing itself.
To clarify this, researchers studied whether eating ultra-processed foods predicted stroke or cognitive decline independently of following healthy diets. They compared it against three well-known healthy eating patterns: the Mediterranean diet, the DASH diet, and the MIND diet.
W. Taylor Kimberly, chief of Neurocritical Care at Massachusetts General Hospital and associate professor at Harvard Medical School, said, “Our group studies risk factors for stroke and cognitive problems, including early biomarkers that predict these diseases years ahead. We found some new biomarkers that were not explained by usual risk factors like high blood pressure, diabetes, smoking, or high cholesterol. This led us to look at other causes, and diet stood out as the strongest factor. We then found that the degree of food processing independently predicted stroke and cognitive decline.”
The study was part of the REGARDS project, which investigates why stroke rates vary across different regions in the U.S. It includes Black and White adults aged 45 and older enrolled between 2003 and 2007.
Participants reported their diets through a detailed questionnaire. Researchers classified foods by processing level using the NOVA system. They focused on unprocessed or minimally processed foods (NOVA1) and ultra-processed foods (NOVA4), measuring intake as a percentage of total food weight.
Two groups were followed over time: 14,175 people without cognitive problems at the start were tested for cognitive decline, and 20,243 people without a stroke history were monitored for stroke occurrence.
The researchers used models that adjusted for many factors like age, sex, race, income, education, blood pressure, diabetes, exercise, depression, and alcohol use. They also controlled for how closely participants followed the Mediterranean, DASH, and MIND diets to isolate the effect of food processing.
Results showed that higher consumption of ultra-processed foods raised the risk of both stroke and cognitive decline. For every 10% increase in ultra-processed foods by weight, the risk of cognitive decline rose by 16%, and stroke risk went up by 8%, even after accounting for other health and lifestyle factors.
Conversely, eating more unprocessed or minimally processed foods was linked to lower risks—a 12% drop in stroke risk and a similar reduction in cognitive decline risk.
Kimberly added, “Though this is not a randomized trial, the evidence suggests that changing diet can influence future brain health outcomes.”
He also noted plans for further research to identify which types of ultra-processed foods pose the greatest risks. “Ultra-processed foods offer benefits like convenience and longer shelf life, so not all carry the same risk. Our goal is to understand these differences to help policymakers make better decisions about the food supply.”
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