Eating ultra-processed foods is not linked to faster mental decline, study finds

A recent study suggests that eating ultra-processed foods does not lead to faster cognitive decline in older adults over a ten-year period. The research, published in the European Journal of Nutrition, provides evidence that overall diet quality may matter more for maintaining brain health as we age than the specific level of food processing. These findings help clarify the complex relationship between what people eat and how their brains change over time.

As the global population ages, the number of people living with dementia is expected to increase dramatically in the coming decades. Because there is currently no cure for dementia, identifying lifestyle factors that can prevent or delay cognitive decline is highly important. Scientists are particularly interested in the role of diet, as healthy eating patterns have consistently been linked to better brain function.

Ultra-processed foods are items made from ingredients that have been heavily modified by chemical processes. They are typically assembled into ready-to-eat products that taste highly appealing, often using artificial flavors, colors, and cosmetic additives. Common examples include packaged cookies, ice cream, sugary drinks, hot dogs, and mass-produced breads.

In recent years, the amount of these heavily processed items in the average daily diet has increased significantly around the world. Scientists conducted the new study because the impact of these foods on brain health remains unclear. Some previous research links diets high in ultra-processed products to a higher risk of dementia and memory loss, while other studies find no such connection.

“Our study was motivated by growing concerns about the health effects of ultra-processed foods. While higher intake of these foods has been linked to various chronic diseases, evidence on cognitive ageing remains limited and inconsistent, particularly in European populations. We therefore examined whether ultra-processed food intake was associated with cognitive decline over time using several validated cognitive tests in a large sample of older Dutch adults,” said study author Hanneke Wijnhoven, an assistant professor in the Department of Health Sciences at Vrije Universiteit Amsterdam.

Because a healthy overall diet tends to protect the brain, scientists wanted to test whether the degree of food processing itself plays a distinct role in cognitive aging. To answer this question, researchers examined data from 1,371 older adults participating in the Longitudinal Aging Study Amsterdam.

The participants were all 55 years of age or older, with an average age of about 67. The researchers analyzed data from a detailed dietary questionnaire that had been administered to these individuals between 2014 and 2015 as part of the broader ongoing study. This survey asked participants to recall how often and how much they ate 238 specific food items over the previous four weeks.

The scientists then categorized every food item from the survey based on its level of processing using a standard system called the NOVA classification. This system divides food into four categories, ranging from completely unprocessed items like fresh vegetables to heavily modified ultra-processed foods. They calculated the total daily intake of ultra-processed foods for each person by weight in grams rather than by calories.

This approach allowed the researchers to account for non-nutritional processing additives and zero-calorie items like artificially sweetened beverages. The participants were divided into four equal groups based on the percentage of ultra-processed foods in their daily diets. On average, ultra-processed items made up about 20 percent of the total food weight consumed by the participants each day.

To track brain health, the researchers looked at cognitive test scores that had been collected from the participants four different times over a ten-year period. The original ongoing project used five separate tests to evaluate different areas of brain function. These areas included global cognition, which is a general measure of overall brain health assessed through a common screening tool.

The dataset also included scores for information processing speed using a coding task, which tracks how quickly a person can understand and react to new information by matching symbols to letters. The records also contained tests of episodic memory, which involves the ability to remember specific past events or learn new lists of words. To measure this, participants in the original project had been asked to memorize and recall a list of fifteen words after a short delay.

Finally, the dataset included measurements of executive function, which covers mental skills like planning, focusing attention, and juggling multiple tasks at the same time. This had been tested by having participants list as many animals as they could think of in one minute and asking them to repeat sequences of numbers backwards. The current scientists then used statistical models on all this gathered information to look for patterns over time.

During this analysis, the researchers adjusted for various lifestyle factors that might affect brain health. These factors included age, sex, education, partner status, total energy intake, physical activity, body mass index, alcohol consumption, smoking, depression, and the presence of chronic diseases. They also factored in a score representing overall diet quality in a separate analysis, ensuring they could isolate the specific impact of ultra-processed foods on the brain.

The researchers found no link between the amount of ultra-processed food consumed and a person’s cognitive abilities over time. They also found no connection between a highly processed diet and faster cognitive decline as the participants aged.

Even the individuals in the group eating the highest percentage of ultra-processed foods experienced the same rate of mental aging as those in the group eating the lowest percentage. The researchers ran an additional test that excluded bread from the ultra-processed category, as Dutch adults eat a lot of mass-produced bread. This secondary analysis yielded the exact same results.

“In this group of older adults, we did not find clear evidence that higher consumption of ultra-processed foods based on the NOVA classification was associated with faster cognitive decline over a 10-year period,” Wijnhoven told PsyPost. “A possible explanation is that overall diet quality may be more important for cognitive health than the level of food processing. In previous analyses within the same cohort, we found that greater adherence to healthy dietary patterns, including the EAT-Lancet reference diet, was associated with less cognitive decline.”

As with all research, the study has some limitations. A primary limitation is that dietary habits were measured using a self-reported survey, which relies heavily on human memory. People might forget exactly what they ate or underreport less healthy food choices, which can affect the accuracy of the data.

Another potential misinterpretation is the idea that all ultra-processed foods are equal in nutritional value. Some processed foods might be fortified with vitamins and minerals, while others are entirely composed of empty calories.

“The NOVA classification has been criticized for not distinguishing between nutritionally poorer (such as sugar-sweetened beverages and processed meats) and more favourable ultra-processed foods (such as some whole-grain breads and certain fortified breakfast cereals), which may partly explain the largely null findings,” Wijnhoven noted.

Future research could focus on examining the exact nutritional profiles of different ultra-processed foods over longer periods of time. Scientists might also track how specific types of processed ingredients, rather than broad categories, interact with brain health over a person’s lifespan. By looking more closely at these individual components, researchers can gain a clearer understanding of how modern diets impact the aging brain.

The study, “Ultra-processed food intake and cognitive decline in older adults,” was authored by Chantal Buis, Mary Nicolaou, Marjolein Visser, Margreet R Olthof, and Hanneke A H Wijnhoven.