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Middle-age people who ate more ultra-processed foods -- white bread, candy bars, cookies, frozen meals, and soda, for example -- were modestly more likely to have subsequent cognitive decline, a prospective study in Brazil showed.

Adults who got 20% or more of their daily calories from ultra-processed foods (UPFs) showed a 28% faster rate of global cognitive decline over 8 years, albeit with a small linear association (β -0.004, 95% CI -0.006 to -0.001, P=0.003), reported Natalia Gomes Gonçalves, PhD, of the University of São Paulo Medical School in Brazil, and co-authors.

That group also showed a 25% faster rate in executive function decline, again with a small linear correlation (β −0.003, 95% CI -0.005 to 0.000, P=0.01), the researchers wrote in .

"Intact cognitive function is key to successful aging," they wrote. "Therefore, despite the small effect size of the association between UPF consumption and cognitive decline, our findings are meaningful to cognitive health."

The results echoed findings published earlier this year that linked ultra-processed foods with dementia risk. Notably, risk was projected in that study to drop sharply when swapping junk food for unprocessed or minimally processed foods.

"Middle age is an important period of life to adopt preventive measures through lifestyle changes, since the choices we make at this age will influence our older years," Gomes Gonçalves said in an email to MedPage Today.

"This does not mean that older adults will not have benefits if they adopt a healthier lifestyle," she added. "Research has shown over and over again that we benefit from healthy choices at any age."

A diet of 20% or more of ultra-processed foods is common, she noted. "Considering a person who eats a total of 2,000 kcal a day, 20% of daily calories from ultra-processed foods are about two 1.5-ounce Kit Kat bars, or five slices of bread, or about a third of an 8.5-ounce package of chips," Gomes Gonçalves wrote.

In the U.S., come from ultra-processed foods. In the U.K. and Canada, that figure is 47-48%; in Brazil, it's 30%.

Gomes Gonçalves and colleagues analyzed ultra-processed food consumption at baseline and subsequent cognitive decline among 10,775 people in the Brazilian Longitudinal Study of Adult Health (). Participants were public servants ages 35 to 74 recruited in six Brazilian cities from 2008 to 2019.

The researchers assessed food and drink intake over the 12 months prior to baseline with a that included 114 items. Foods were classified by their extent of industrial processing using the system.

Cognitive evaluations included immediate and delayed word recall, word recognition, phonemic and semantic verbal fluency tests, and the Trail-Making Test part B, which were conducted over a median follow-up of 8 years. Individuals were tested up to three times every 4 years.

Mean age at baseline was 51.6 years. About 55% of participants were women, 53% were white, and 57% had at least a college degree. Total daily calorie intake averaged 2,856 kcal, with 27% (785 kcal) from ultra-processed foods. The researchers grouped the percentage contribution of ultra-processed food into quartiles (0-19.9%, 20-26.7%, 26.8-34.1%, and 34.2-72.7%), comparing the lowest-intake group against all others combined.

Age modified the effect between ultra-processed foods and cognitive function. People younger than 60 who ate 20% or more of their daily calories as ultra-processed foods showed faster global cognition decline than their same-age counterparts who consumed less junk food (β -0.006, 95% CI -0.009 to -0.003, P<0.001).

"The interesting thing about the NOVA classification system is that it classifies foods based on the industrial processing they go through," Gomes Gonçalves observed. "To make healthier choices, one can dedicate more time to cooking meals from scratch at home."

"For example, instead of buying frozen pizza, one could buy separate ingredients, make homemade dough, and use fresh ingredients as toppings," she noted. "It's possible to make healthier food choices within our means even if our access to healthy food is limited. We just need to dedicate the time and energy."

Attrition is a concern for a long-term study, the researchers acknowledged. People under age 55 didn't have a cognitive assessment during their second visit due to study design. The findings relied on self-reported data from food frequency questionnaires, which may be subject to bias and misreporting.

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