Editor’s Note: Sign up for CNN’s Eat, But Better: Mediterranean Style. Our eight-part guide shows you a delicious expert-backed eating lifestyle that will boost your health for life.
We all eat them — ultraprocessed foods such as frozen pizza and ready-to-eat meals make our busy lives much easier. Besides, they are just darn tasty — who isn’t susceptible to hot dogs, sausages, burgers, french fries, sodas, cookies, cakes, candy, doughnuts and ice cream, to name just a few?
If more than 20% of your daily calorie intake is ultraprocessed foods, however, you may be raising your risk for cognitive decline, a new study found.
That amount would equal about 400 calories a day in a 2,000-calories-a-day diet. For comparison, a small order of fries and regular cheeseburger from McDonald’s contains a total of 530 calories.
The part of the brain involved in executive functioning — the ability to process information and make decisions — is especially hard hit, according to the study published Monday in JAMA Neurology.
In fact, men and women who ate the most ultraprocessed foods had a 28% faster rate of global cognitive decline and a 25% faster rate of executive function decline compared with people who ate the least amount of overly processed food, the study found.
“While this is a study of association, not designed to prove cause and effect, there are a number or elements to fortify the proposition that some acceleration in cognitive decay may be attributed to ultraprocessed foods,” said Dr. David Katz, a specialist in preventive and lifestyle medicine and nutrition, who was not involved in the study.
“The sample size is substantial, and the follow-up extensive. While short of proof, this is robust enough that we should conclude ultraprocessed foods are probably bad for our brains.”
There was an interesting twist, however. If the quality of the overall diet was high — meaning the person also ate a lot of unprocessed, whole fruits and veggies, whole grains and healthy sources of protein — the association between ultraprocessed foods and cognitive decline disappeared, Katz said.
“Ultraprocessed foods drag diet quality down, and thus their concentration in the diet is an indicator of poor diet quality in most cases,” Katz said. “Atypical as it seems, apparently some of the participants managed it. And when diet quality was high, the observed association between ultraprocessed foods and brain function abated.”
It’s not a lot of calories
The study, presented Monday at the 2022 Alzheimer’s Association International Conference in San Diego, followed over 10,000 Brazilians for up to 10 years. Just over half of the study participants were women, White or college educated, while the average age was 51.
Cognitive testing, which included immediate and delayed word recall, word recognition and verbal fluency were performed at the beginning and end of the study, and participants were asked about their diet.
“In Brazil, ultraprocessed foods make up 25% to 30% of total calorie intake. We have McDonald’s, Burger King and we eat a lot of chocolate and white bread. It’s not very different, unfortunately, from many other Western countries,” said coauthor Dr. Claudia Suemoto, an assistant professor in the division of geriatrics at the University of São Paulo Medical School.
“Fifty-eight percent of the calories consumed by United States citizens, 56.8% of the calories consumed by British citizens, and 48% of the calories consumed by Canadians come from ultraprocessed foods,” Suemoto said.
Ultraprocessed foods are defined as “industrial formulations of food substances (oils, fats, sugars, starch, and protein isolates) that contain little or no whole foods and typically include flavorings, colorings, emulsifiers, and other cosmetic additives,” according to the study.
“People who consumed more than 20% of daily calories from processed foods had a 28% faster decline in global cognition and a 25% faster decline in executive functioning compared to people who ate less than 20%,” said study coauthor Natalia Gonçalves, a researcher in the department of pathology at the University of São Paulo Medical School.
It’s not just the brain
In addition to the impact on cognition, ultraprocessed foods are already known to raise the risk of obesity, heart and circulation problems, diabetes, cancer and a shorter life span.
“Ultraprocessed foods in general are bad for every part of us,” said Katz, president and founder of the nonprofit True Health Initiative, a global coalition of experts dedicated to evidence-based lifestyle medicine.
Ultaprocessed foods are usually high in sugar, salt and fat, all of which promote inflammation throughout the body, which is “perhaps the most major threat to healthy aging in the body and brain,” said Dr. Rudy Tanzi, professor of neurology at Harvard Medical School and director of the genetics and aging research unit at Massachusetts General Hospital in Boston. He was not involved in the study.
“Meanwhile, since they are convenient as a quick meal, they also replace eating food that is high in plant fiber that is important for maintaining the health and balance of the trillions of bacteria in your gut microbiome,” Tanzi added, “which is particularly important for brain health and reducing risk of age-related brain diseases like Alzheimer’s disease.”
What to do
How can you keep this from happening to you? If you include ultraprocessed foods in your diet, try to counter these by also eating high-quality, whole foods such as fruits, vegetables and whole grains.
“The conclusion suggested here is that ultraprocessed foods are, indeed, an important ‘ingredient,’ but the exposure that should be the focus of public health efforts is overall diet quality,” Katz said.
One easy way to ensure diet quality is to cook and prepare your food from scratch, Suemoto said.
“People need to know they should cook more and prepare their own food from scratch. I know. We say we don’t have time but it really doesn’t take that much time,” Suemoto said.
“And it’s worth it because you’re going to protect your heart and guard your brain from dementia or Alzheimer’s disease,” she added. “That’s the take-home message: Stop buying things that are superprocessed.”