Key Takeaways

  • Researchers examined the association between the consumption of ultra-processed foods—items that contain additives and preservatives such as snacks and sweets—and rates of stroke and cognitive impairment
  • They found that the increased consumption of these foods was associated with a higher risk of both stroke and cognitive decline, and the risk was even more elevated in Black patients
  • Even modest cutbacks in the consumption of ultra processed foods were associated with positive health benefits

BOSTON – Long-term consumption of ultra-processed foods (UPFs)—foods altered with additives and preservatives, which have become staples in the diets of countless Americans—are associated with an increased risk of stroke and cognitive impairment, researchers at Massachusetts General Hospital (MGH), a founding member of the Mass General Brigham healthcare system, have found.

According to research published online in Neurology®, the medical journal of the American Academy of Neurology, the team also found that eating more minimally processed or unprocessed foods was associated with commensurate improvements in brain health and reductions in serious neurological outcomes.

“It’s important for individuals to pay attention to not just what foods they eat, but how those foods are processed before they eat them,” says W. Taylor Kimberly, MD, PhD, chief of the Division of Neurocritical Care at MGH, and senior author of the study.

“We’ve shown that increased intake over time of ultra-processed foods can impact the two most common and significant causes of neurological disability -- stroke and cognitive impairment. The good news is that even modest cutbacks in consumption of UPFs are associated with meaningful brain health benefits.”

The majority of caloric intake by consumers in the United States can be tied to ultra-processed foods, which in recent decades have become ubiquitous in grocery and convenience stores. They are foods to which fats, starches, sugars, salts, and hydrogenated oils have been added to enhance their taste, flavor, and shelf-life. Common examples include ready-to-eat snacks and meals, sugary beverages, sweetened breakfast cereals, and cured meats. Concurrent with their marketplace growth has been an expanding body of clinical evidence linking UPFs to adverse health conditions, such as cardiovascular disease, obesity, and diabetes.

In its study, the MGH team explored the association between these highly processed foods and the risk of incident stroke and cognitive impairment. Findings were based on an analysis of roughly 10 years of data from REGARDS, a research project managed by the University of Alabama at Birmingham (UAB) School of Public Health, designed to assess the cause of stroke in a geographically dispersed population of over 30,000 adults.

Researchers found that increased consumption of UPFs resulted in a higher risk of stroke (9 percent increased risk) and accelerated cognitive decline (12 percent increased risk), and that the association between UPFs and stroke was greater among Black participants (15 percent increased risk), possibly reflecting this group’s higher incidence of hypertension.

Researchers also looked at specific diets like Mediterranean, DASH (Dietary Approaches to Stop Hypertension), and MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) that encourage fresh fruits and vegetables while minimizing red and processed meats. “We found these diets were independently associated with reduced risk of stroke and cognitive decline,” notes lead author Varun Bhave of Harvard Medical School.

“We also found that the degree of food processing not only plays an important role in overall brain health, but also provides complementary information to other dietary patterns doctors often recommend, such as Mediterranean, DASH and MIND.”

The next step for the MGH and UAB teams is to better understand the biological mechanisms that link UPF intake to brain health, including the role of the gut microbiome in metabolizing the foods we eat. As Kimberly points out, this pathway could lead to the development of biomarkers in the blood that assess UPF intake and could potentially be used as part of personalized medicine plans to help individuals gauge if changing their diet is putting them on the road to improved brain health.

“While our study clearly sounds a warning, it also provides hope that there are things we can do as individuals and which policymakers can do on a national scale to reduce UPFs from our daily diets,” says Kimberly. “As we found, even incremental changes are associated with a significant difference in improving our brain health, along with lowering our risk for stroke and cognitive decline.”

Kimberly is a critical care neurologist and associate professor of Neurology at Harvard Medical School. Bhave is a Harvard Medical School student. Co-authors include M. Ryan Irvin, PhD, with the Department of Epidemiology, University of Alabama at Birmingham, and Carol Oladele, PhD, MPH, director of the Equity Research and Innovation Center at Yale School of Medicine.

The study was funded by the National Institute of Neurological Disorders and Stroke (NINDS).