We all eat them - ultra-processed 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 percent of your daily calorie intake is ultra-processed 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 2000-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.
Men and women in the study who ate the most ultra-processed foods had a 25 percent faster rate of executive function decline and a 28 percent faster rate of overall cognitive impairment compared with those who ate the least amount of overly processed food.
"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 ultra-processed 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 ultra-processed 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 ultra-processed foods and cognitive decline disappeared, Katz said.
"Ultra-processed 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 ultra-processed foods and brain function abated."
A lot of ultra-processed foods
The study 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, was performed at the beginning and end of the study, and participants were asked about their diet.
"In Brazil, ultra-processed foods make up 25 percent to 30 percent 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," coauthor Dr Claudia Suemoto, an assistant professor in the division of geriatrics at the University of São Paulo Medical School, told CNN when the study abstract was released in August.
"Fifty-eight percent of the calories consumed by United States citizens, 56.8 percent of the calories consumed by British citizens, and 48 percent of the calories consumed by Canadians come from ultra-processed foods," Suemoto said.
Ultra-processed 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.
Those in the study who ate the most ultra-processed foods were "more likely to be younger, women, White, had higher education and income, and were more likely to have never smoked, and less likely to be current alcohol consumers," the study found.
It's not just the brain
In addition to the impact on cognition, ultra-processed foods are already known to raise the risk of obesity, heart and circulation problems, diabetes, cancer and a shorter life span.
"Ultra-processed 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.
Ulta-processed 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 ultra-processed 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 ultra-processed 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.
"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. That's the take-home message: Stop buying things that are super processed."
CNN
