Results from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), which included more than 10,000 people aged 35 and older, showed that higher intake of UPF was significantly associated with a faster rate of decline in executive and global cognitive function.
“These findings show that lifestyle choices, particularly high intake of ultraprocessed foods, can influence our cognitive health many years later,” coinvestigator Natalia Goncalves, PhD, University of São Paulo, Brazil, said in an interview.
The study was published online in JAMA Neurology.
The study’s findings were presented in August at the Alzheimer’s Association International Conference (AAIC) 2022 and were reported by this news organization at that time.
High sugar, salt, fat
The new results align with another recent study linking a diet high in UPFs to an increased risk for dementia.
UPFs are highly manipulated, are packed with added ingredients, including sugar, fat, and salt, and are low in protein and fiber. Examples of UPFs are soft drinks, chips, chocolate, candy, ice cream, sweetened breakfast cereals, packaged soups, chicken nuggets, hot dogs, and fries.
The ELSA-Brasil study comprised 10,775 adults (mean age, 50.6 years at baseline; 55% women; 53% White) who were evaluated in three waves approximately 4 years apart from 2008 to 2017.
Information on diet was obtained via food frequency questionnaires and included details 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 by use of a standardized battery of tests.
During median follow-up of 8 years, people who consumed more than 20% of daily calories from UPFs (quartiles 2-4) experienced a 28% faster rate of decline in global cognition (beta = –0.004; 95% confidence interval [CI], –0.006 to –0.001; P = .003) and a 25% faster rate of decline in executive function (beta = –0.003, 95% CI, –0.005 to 0.000; P = .01) compared to peers in quartile 1 who consumed less than 20% of daily calories from UPFs.
The researchers did not investigate individual groups of UPFs.
However, Dr. Goncalves noted that some studies have linked the consumption of sugar-sweetened beverages with lower cognitive performance, lower brain volume, and poorer memory performance. Another group of ultraprocessed foods, processed meats, has been associated with increased all-cause dementia and Alzheimer’s disease.
Other limitations include the fact that self-reported diet habits were assessed only at baseline using a food frequency questionnaire that was not designed to assess the degree of processing.
While analyses were adjusted for several sociodemographic and clinical confounders, the researchers said they could not exclude the possibility of residual confounding.
Also, since neuroimaging is not available in the ELSA-Brasil study, they were not able to investigate potential mechanisms that could explain the association between higher UPF consumption and cognitive decline.
Despite these limitations, the researchers said their findings suggest that “limiting UPF consumption, particularly in middle-aged adults, may be an efficient form to prevent cognitive decline.”
Weighing the evidence
Several experts weighed in on the results in a statement from the UK nonprofit organization, Science Media Centre.
Kevin McConway, PhD, with Open University, Milton Keynes, England, said it’s important to note that the study suggests “an association, a correlation, and that doesn’t necessarily mean that the cognitive decline was caused by eating more ultra-processed foods.”
He also noted that some types of cognitive decline that are associated with aging occurred in participants in all four quartiles, which were defined by the percentage of their daily energy that came from consuming UPFs.
“That’s hardly surprising – it’s a sad fact of life that pretty well all of us gradually lose some of our cognitive functions as we go through middle and older age,” Dr. McConway said.
“The study doesn’t establish that differences in speed of cognitive decline are caused by ultra-processed food consumption anyway. That’s because it’s an observational study. If the consumption of ultra-processed food causes the differences in rate of cognitive decline, then eating less of it might slow cognitive decline, but if the cause is something else, then that won’t happen,” Dr. McConway added.
Gunter Kuhnle, PhD, professor of nutrition and food science, University of Reading, England, noted that UPFs have become a “fashionable term to explain associations between diet and ill health, and many studies have attempted to show associations.
“Most studies have been observational and had a key limitation: It is very difficult to determine ultra-processed food intake using methods that are not designed to do so, and so authors need to make a lot of assumptions. Bread and meat products are often classed as ‘ultra-processed,’ even though this is often wrong,” Dr. Kuhnle noted.
“The same applies to this study – the method used to measure ultra-processed food intake was not designed for that task and relied on assumptions. This makes it virtually impossible to draw any conclusions,” Dr. Kuhnle said.
Duane Mellor, PhD, RD, RNutr, registered dietitian and senior teaching fellow, Aston University, Birmingham, England, said the study does not change how we should try to eat to maintain good brain function and cognition.
“We should try to eat less foods which are high in added sugar, salt, and fat, which would include many of the foods classified as being ultra-processed, while eating more in terms of both quantity and variety of vegetables, fruit, nuts, seeds, and pulses, which are known to be beneficial for both our cognitive and overall health,” Dr. Mellor said.
The ELSA-Brasil study was supported by the Brazilian Ministry of Health, the Ministry of Science, Technology and Innovation, and the National Council for Scientific and Technological Development. The authors as well as Dr. McConway, Dr. Mellor, and Dr. Kuhnle have disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.