High intake of ultra-processed foods linked to greater dementia risk in older adults

A recent study published in the American Journal of Public Health suggests that older adults who consume high amounts of ultra-processed foods face a greater risk of developing dementia and other forms of cognitive decline. The findings provide evidence that replacing industrially manufactured foods with fresh, unprocessed alternatives tends to offer a protective benefit for maintaining brain health in later life.

Ultra-processed foods are items produced in industrial settings that contain chemical additives, artificial flavors, and preservatives. These ingredients are designed to make the products taste better and last longer on store shelves. Examples include sugary sodas, packaged sweet snacks, sweetened breakfast cereals, and mass-produced frozen meals. These foods tend to be high in added sugars, sodium, and saturated fats while lacking important dietary fiber.

In the United States, these highly processed items account for a large portion of the daily calorie intake for many adults. Their convenience and widespread availability have led to an increase in consumption, particularly among older populations. High intake of these foods is already linked to physical health conditions like obesity, diabetes, and heart disease.

In recent years, scientists have turned their attention to the potential effects of a highly processed diet on the human brain. Some evidence hints that poor diet quality plays a role in cognitive decline, but past studies have produced mixed findings regarding milder cognitive issues. One prior American longitudinal study actually found no significant association between ultra-processed diets and general cognitive impairment.

That previous work, however, did not measure food intake by weight, a method that often provides a more accurate picture of how much of a person’s diet consists of these items. The authors of the new paper sought to fill this gap in the literature. They wanted to examine how the sheer volume of ultra-processed food consumed relates to specific health outcomes, including full dementia and milder forms of cognitive impairment.

To explore this relationship, the researchers analyzed data from the Health and Retirement Study. This is a large, nationally representative longitudinal survey of older Americans. The final sample included 5,370 adults aged 50 and older. To ensure they were observing new cases of cognitive decline, the scientists excluded anyone who already had a dementia diagnosis or memory problems at the start of the data collection period.

Participants completed a detailed food frequency questionnaire in 2013, reporting how often they ate various items over the previous year. The researchers then categorized these foods based on their level of industrial processing. They calculated the percentage of each person’s total daily diet that came from ultra-processed foods, adjusting the measurements by weight in grams rather than just counting daily caloric servings.

The scientists broke the ultra-processed items down into thirteen mutually exclusive subgroups. These categories included whole grains, dairy, fats and oils, processed meats, snacks and sweets, and sugar-sweetened beverages. Sugar-sweetened beverages and other drinks ended up being the largest contributors to the total ultra-processed food intake among the participants.

To track brain health, the participants underwent cognitive assessments every two years between 2014 and 2020. These tests involved tasks such as counting backward, remembering a list of words immediately and after a delay, and subtracting numbers in a series. Based on a twenty-seven-point scoring system, participants were classified as having normal cognitive function, cognitive impairment without dementia, or full dementia.

Cognitive impairment without dementia refers to a noticeable decline in mental abilities, such as memory and thinking skills, that is not severe enough to interfere entirely with daily life. People with this condition are at a higher risk of eventually developing full dementia. The researchers used a composite category that combined both of these conditions for parts of their statistical analysis.

The researchers tracked the participants for an average of nearly nine years. During that time, they identified 266 new cases of dementia, 1,191 cases of cognitive impairment without dementia, and 1,310 cases of the composite category. They then compared the cognitive outcomes of the individuals who ate the highest amounts of ultra-processed foods to those who ate the least.

Adults in the highest one-fifth of ultra-processed food consumption had a 58 percent higher risk of developing dementia compared to those in the lowest one-fifth. The highest consumers also faced a 46 percent higher risk of developing cognitive impairment without dementia. The researchers observed these elevated risks even after adjusting for factors like age, gender, race, education, wealth, physical activity, and smoking habits.

When analyzing specific types of ultra-processed items, the authors found that processed meat was the only individual category significantly linked to higher risks across all cognitive outcomes. Unprocessed or minimally processed foods, such as fresh fruits, vegetables, and plain grains, showed the exact opposite pattern. Higher consumption of these natural foods was associated with a significantly lower risk of both dementia and milder cognitive impairment.

The scientists also explored whether social factors influenced this relationship. They created a social isolation score based on whether participants lived alone, were unmarried, or had infrequent contact with friends, family, and social clubs. The association between poor diet and cognitive impairment tended to be stronger among older adults who experienced social isolation, suggesting this demographic might be particularly vulnerable.

While the study provides extensive evidence linking diet and brain health, it does have some limitations. The food questionnaire relied on participants remembering and reporting their own eating habits, which can sometimes lead to unintentional inaccuracies. Because the survey was not explicitly designed to track industrial food processing, the researchers may have underestimated the true amount of ultra-processed foods people consumed on a daily basis.

Additionally, the cognitive outcomes were based on survey-based mental tests rather than official clinical diagnoses from neurologists. Although these tests are widely used and validated in population research, they may occasionally misclassify a person’s true cognitive status. The study design also leaves open the possibility of unmeasured lifestyle factors subtly influencing both dietary choices and brain health over time.

There is also a chance that early, undetected changes in the brain could influence eating habits before a formal cognitive issue is recognized. People experiencing early memory problems might shift toward eating more convenient, packaged meals out of necessity. The researchers attempted to account for this by excluding individuals who developed cognitive impairment within the first two years of the study, but some reverse causation might still exist.

The biological reasons behind these findings require further investigation. The authors suggest that high consumption of industrial additives and sugars might alter gut bacteria, increase oxidative stress, and promote chronic inflammation in the body. These physical responses could theoretically disrupt the biological pathways that maintain healthy brain tissue and support cognitive function.

Future research could focus on longer tracking periods and more precise dietary logging methods, such as daily food diaries. Health professionals could use this expanding body of evidence to encourage older adults to prioritize fresh foods in their daily routines. Public health policies might also support these individual choices by making minimally processed ingredients more accessible and affordable in communities.

The study, “Ultraprocessed Foods and the Risk of Cognitive Impairment and Dementia in Older US Adults: 2013–2020 Health and Retirement Study,” was authored by Heejin Lee, Claire T. McEvoy, Euridice Martinez Steele, Neha Khandpur, Steven G. Heeringa, Lindsay H. Ryan, Kenneth M. Langa, Julia A. Wolfson, and Cindy W. Leung.