August 01, 2022
More research suggests that eating a diet high in ultraprocessed foods (UPFs) is harmful for the aging brain.
Results from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), which included participants aged 35 and older, showed that higher intake of UPF was significantly associated with a faster rate of decline in both executive and global cognitive function.
"Based on these findings, doctors might counsel patients to prefer cooking at home [and] choosing fresher ingredients instead of buying ready-made meals and snacks," co-investigator Natalia Goncalves, PhD, University of Sao Paulo Medical School, Brazil, told Medscape Medical News.
Presented at the Alzheimer's Association International Conference (AAIC) 2022, the findings align with those from a study published last week in Neurology. As reported at the time by Medscape Medical News, that study linked a diet high in UPFs to an increased risk for dementia.
Increasing Worldwide Consumption
UPFs are highly manipulated, are packed with added ingredients, including sugar, fat, and salt, and are low in protein and fiber. Examples of UPFs include soft drinks, chips, chocolate, candy, ice cream, sweetened breakfast cereals, packaged soups, chicken nuggets, hotdogs, fries, and many more.
Over the past 30 years, there has been a steady increase in consumption of UPFs worldwide. They are thought to induce systemic inflammation and oxidative stress and have been linked to a variety of ailments, such as overweight/obesity, cardiovascular disease, and cancer.
UPFs may also be a risk factor for cognitive decline, although data are scarce as to their effects on the brain.
To investigate, Goncalves and colleagues evaluated longitudinal data on 10,775 adults (mean age, 50.6 years; 56% women; 55% White) who participated in the ELSA-Brasil study. They were evaluated in three waves (2008–2010, 2012–2014, and 2017–2019).
Information on diet was obtained via food frequency questionnaires and included information regarding consumption of unprocessed foods, minimally processed foods, and UPFs.
Participants were grouped according to UPF consumption quartiles (lowest to highest). Cognitive performance was evaluated using a standardized battery of tests.
Using linear mixed effects models that were adjusted for sociodemographic, lifestyle, and clinical variables, the investigators assessed the association of dietary UPFs as a percentage of total daily calories with cognitive performance over time.
During a median follow-up of 8 years, UPF intake in quartiles 2 to 4 (vs quartile 1) was associated with a significant decline in global cognition (P = .003) and executive function (P = .015).
"Participants who reported consumption of more than 20% of daily calories from ultraprocessed foods had a 28% faster rate of global cognitive decline and a 25% faster decrease of the executive function compared to those who reported eating less than 20% of daily calories from ultraprocessed foods," Goncalves reported.
"Considering a person who eats a total of 2000 kcal a day, 20% of daily calories from ultraprocessed foods are about two 1.5 oz bars of KitKat, or five slices of bread, or about a third of an 8.5-oz package of chips," she explained.
Goncalves noted that the reasons UPFs may harm the brain remain a "very relevant but not yet well-studied topic."
Hypotheses include secondary effects from cerebrovascular lesions or chronic inflammation processes. More studies are needed to investigate the possible mechanisms that might explain the harm of UPFs to the brain, she said.
'Troubling but Not Surprising'
Commenting on the study for Medscape Medical News, Percy Griffin, PhD, director of scientific engagement for the Alzheimer's Association, said there is "growing evidence that what we eat can impact our brains as we age."
He added that many previous studies have suggested it is best for the brain for one to eat a heart-healthy, balanced diet that is low in processed foods and high in whole, nutritional foods, such as vegetables and fruits.
"These new data from the Alzheimer's Association International Conference suggest eating a large amount of ultraprocessed food can significantly accelerate cognitive decline," said Griffin, who was not involved with the research.
He noted that an increase in the availability and consumption of fast foods, processed foods, and UPFs is due to a number of socioeconomic factors, including low access to healthy foods, less time to prepare foods from scratch, and an inability to afford whole foods.
"Ultraprocessed foods make up more than half of American diets. It's troubling but not surprising to see new data suggesting these foods can significantly accelerate cognitive decline," Griffin said.
"The good news is there are steps we can take to reduce risk of cognitive decline as we age. These include eating a balanced diet, exercising regularly, getting good sleep, staying cognitively engaged, protecting from head injury, not smoking, and managing heart health," he added.
Past research has suggested that the greatest benefit is from engaging in combinations of these lifestyle changes and that they are beneficial at any age, he noted.
"Even if you begin with one or two healthful actions, you're moving in the right direction. It's never too early or too late to incorporate these habits into your life," Griffin said.
The study had no specific funding. Goncalves and Griffin have reported no relevant financial relationships.
Nutrition and Healthy Eating Resources
Medscape, August 01, 2022.
Alzheimer's Association International Conference (AAIC) 2022: Abstract 63301. Presented August 1, 2022.