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A recent study suggesting a link between ultraprocessed foods and cognitive decline further adds to the growing body of evidence showing that a nutritious diet can help support a healthy brain.
But just how much can a poor diet impact dementia, like Alzheimer’s disease? What exactly are ultraprocessed foods? And what type of diet boosts the brain?
Study linking ultraprocessed foods to cognitive decline
Let’s start with the study, which was published online in December 2022 by JAMA Neurology. It followed about 11,000 Brazilian public service workers (ages 35 to 74 at the study’s start) from 2008 to 2019. Researchers collected data about participants’ diets at the beginning of the study, then gave them cognitive tests up to three times a year every four years.
People whose diets had the highest levels of ultraprocessed foods (20% of calories or more) showed a 28% faster rate of overall cognitive decline, according to the researchers from the University of São Paulo, other universities in Brazil, and the Harvard T.H. Chan School of Public Health in Boston.
Those eating the highest levels of ultraprocessed foods (UPFs) also showed a 25% faster rate of executive function decline. (Examples of executive functions are judgment, decision-making, problem-solving, planning and self-control.)
The researchers also discovered that these high-UPF consumers seemed to be protected from overall decline if they scored high on overall healthy eating scores (based on the Mediterranean-DASH Intervention for Neurodegenerative Delay – or MIND – diet).
Do processed foods cause dementia?
While it’s possible a very poor diet can lead to cognitive issues all by itself, it’s unlikely to cause conditions like Alzheimer’s disease. However, it’s possible it will bring them on more quickly if you’re at risk, says Douglas Scharre, MD, director of the Division of Cognitive and Memory Disorders in the Department of Neurology at The Ohio State University Wexner Medical Center.
For example, if you’re at risk for other conditions linked to cognitive decline – such as heart disease, stroke, a genetic condition, diabetes, sleep apnea or cancer requiring chemotherapy – dementia could progress more quickly with a poor diet, Dr. Scharre says. And too much sugar and fatty foods and not enough fresh fruits and vegetables can further deteriorate a mind already being ravaged by Alzheimer’s disease.
“Your brain functions better with good nutrition,” Dr. Scharre says. “If you’re consistently having a bad diet, that doesn't help your brain process things as well, and if you're prone to one of these degenerative conditions that cause dementia, that's not going to help. It’s going to make cognitive issues and dementia come on faster and progress more quickly.”
The brain-nutrition link is also meaningful, Dr. Scharre adds, because it indicates that there may be a portion of cognitive decline that can be controlled, resulting in patients with more independence and a higher quality of life.
“I don’t doubt the significance of the impact of a brain healthy diet, because there are so many people who have dementia or cognitive issues as they get older. If you can control 5%, just for example, of your brain health with a healthy diet, your brain is going to function better and that means less care that other people have to do for you, and that’s less cost and you have less home health care and you have fewer medical appointments,” he says.
“I just have a strong feeling that the impact of something like this is a lot more than anyone really thinks.”
What are ultraprocessed foods?
According to the December study, 58% of the calories eaten by people in the U.S. are ultraprocessed foods.
The authors define them as “formulations of processed 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.” They list as examples “sweet and savory snacks, confectionery, breakfast cereals, ice cream, sugar-sweetened beverages, processed meats, and ready-to-eat frozen meals.”
More simply put, look at a product’s ingredient list and ask yourself, “If you had the recipe, could you buy all those ingredients and remake that product at home?” says Lori Chong, MBA, RDN, LD, a registered dietitian and certified diabetes educator at the Ohio State Wexner Medical Center. If the answer is no, there’s a good chance the product is an ultraprocessed food.
“I use the term ‘empty calorie.’ I typically recommend people keep those types of foods to less than 10% of calories,” Chong says. “It's important for us to not get the message that we can't eat this food, because then it's the forbidden fruit phenomenon and people want more. Those things just need to be a smaller part of our diet.”
Eating to limit ultraprocessed foods and protect the brain
The things that keep the rest of the body healthy keep our brains healthy, too, Chong explains, like fiber from whole grains, beans and lentils, vegetables, fruits, nuts and seeds and a limited amount of saturated fats and animal foods.
“Nutrition makes a difference in every area of your health, including your brain health and dementia prevention, and it's better to start early,” Chong says. “Use nutrition as a preventive strategy, whether we're talking about dementia prevention, cancer prevention, diabetes prevention or heart disease prevention. You're going to make a bigger difference if you're starting early and being fairly consistent. This just kind of goes back to ‘an ounce of prevention is worth a pound of cure.’”
Changing diet once we already have disease, she says, can require extreme measures to result in benefits.
The MIND diet, recommended for cognitive support, combines two diets to target cognitive decline: The Mediterranean diet and the DASH (Dietary Approaches to Stop Hypertension) diet. It recommends 10 healthy brain foods and places limits on five unhealthy brain foods.
Dr. Scharre says it’s always a good time to make a change toward a brain-healthy diet. Some damage, as long as it isn’t permanent from having had a stroke or disease that kills nerve cells, is reversible, especially if you pair nutrition with mental stimulation.
“Your brain’s very flexible,” he says. “There's plenty of evidence to suggest that cells are resilient. They’ll go back to working again. You can start to build up new synapses and new connections in the brain.”
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