Eating a diet high in ultraprocessed foods is associated with an increased risk of dementia, according to new research, adding to the growing list of health problems linked to foods such as packaged cookies, hot dogs and chips.
In a study published Wednesday in the American Journal of Public Health, the group of people who reported eating the highest amount of ultraprocessed foods had a 58% higher risk of later developing dementia and a 46% increased risk of developing cognitive impairment than those who said they ate the least.
The study involved more than 5,300 U.S. adults ages 50 and older and followed them for almost nine years, on average. The researchers, from the Harvard T.H. Chan School of Public Health and other institutions, aimed to home in on the impact of ultraprocessed foods by accounting for a range of other factors that affect health, including education, income, smoking, physical activity and alcohol use.
The results add to a body of scientific evidence linking diets high in ultraprocessed foods to health problems including obesity, cardiovascular disease and Type 2 diabetes. The Trump administration has made a series of moves under the direction of Health and Human Services Secretary Robert F. Kennedy Jr. to nudge people away from many foods considered ultraprocessed. The administration issued new dietary guidelines that advise Americans to avoid highly processed foods with added sugars and salt, such as packaged chips, cookies and candy.Nutrition researchers generally define ultraprocessed foods as items containing ingredients that wouldn’t generally be found in a home kitchen, such as emulsifiers—used to improve the texture of food—and high-fructose corn syrup.
The new study found that diets high in minimally processed foods, such as fresh fruits, vegetables, whole grains, fish and unprocessed meats, were linked to a decreased risk of dementia and cognitive impairment. People who ate the most minimally processed foods had a 41% lower risk of dementia compared with those who ate the least.
Many ultraprocessed foods are unhealthy because they are high in added sugars, sodium and saturated fat. But those factors alone don’t seem to fully explain their links to health problems, nutrition researchers say.
The risks weren’t only for people who ate the most ultraprocessed foods in the new study. Those who had more moderate levels of consumption also had a higher risk of dementia and cognitive impairment compared with the group who had the lowest.
“Just to say, ‘well, I don’t eat all my calories from ultraprocessed foods, I’m safe.’ It really shows there may not be a safe level,” said Cindy W. Leung, associate professor of public health nutrition at Harvard T.H. Chan and a co-author of the new study. The paper was part of a special edition of the American Journal of Public Health devoted to ultraprocessed foods.
The scientists analyzed the impact of specific types of ultraprocessed foods. They found that processed meats, such as bacon, hot dogs and sliced ham, were linked to the highest risk of dementia and cognitive impairment.
In the study, the group that ate the most ultraprocessed foods had an average intake of nearly a kilogram a day of such products, more than four times as high as those who ate the least.
Because the research is observational, it can’t prove that ultraprocessed foods cause dementia and cognitive impairment.
One likely explanation for the link is that diets high in ultraprocessed foods are associated with obesity, Type 2 diabetes and cardiovascular disease, and those illnesses raise the risk of dementia, said Dr. Alex Henney, an endocrinologist at the University of Liverpool who has studied ultraprocessed foods and dementia.
Emerging research is revealing more direct potential reasons for the link between ultraprocessed foods and dementia, said Dr. Dariush Mozaffarian, a cardiologist and director of the Food Is Medicine Institute at Tufts University.
Certain additives common in ultraprocessed foods, like emulsifiers, can alter the gut microbiome in a way that might cause inflammation. Inflammation has been implicated in many health problems, including dementia.
Nitrites, used as preservatives in processed meats, can also drive inflammation. And in animal studies, artificial sweeteners such as aspartame have been shown to cause problems with learning and memory, Mozaffarian notes.
Write to Andrea Petersen at andrea.petersen@wsj.com
