- Researchers investigated the effects of ultra-processed foods such as pizza, white bread, and chocolate on cognitive performance in older adults.
- They found that ultra-processed foods are linked to reduced language and executive function in older adults without chronic illness.
- They noted that reducing consumption of ultra-processed foods may prevent cognitive decline and reduce dementia risk.
Ultra-processed foods (UPF) are increasingly replacing traditional diets based on minimally-processed and unprocessed foods worldwide.
In the United States, UPFs comprise 57% of the energy intake among the adult population and 67% among children and adolescents.
Processed foods typically include two or three ingredients and include:
- canned vegetables
- salted nuts
- cheese
- plain yogurt
UPFs contain no whole foods, undergo several industrial processes, and contain ingredients including flavorings, colorings, and cosmetic additives. Examples include:
- packaged snacks
- chocolate
- pre-prepared dishes such as pizza and pasta
- breakfast cereals
Increased consumption of UPFs is linked to reduced nutritional quality of diets, and chronic conditions, including obesity, metabolic conditions, and cardiovascular disease (CVD).
Knowing more about how UPFs impact overall health could help shape dietary recommendations to improve public health.
Recently, researchers investigated the effects of UPFs on cognitive performance in older adults.
They found that UPF consumption was linked to worse performance in language and executive function cognitive tests among those without chronic conditions. They noted that decreasing UPF consumption may help improve impaired cognition among older adults.
The study was published in the European Journal of Nutrition.
Animal fluency test
For the study, the researchers examined data from 2,713 individuals aged 60 years and older from the U.S. National Health and Nutrition Examination Survey (NHANES) 2011- 2014.
Researchers subjected the participants to various cognitive tests and assessed their dietary intake via two 24-hour diet recalls.
In the end, the researchers found no significant link between overall cognitive test scores and UPF intake.
However, UPF consumption was linked to worse performance in Animal Fluency tests, which assess language and executive function, only among those without pre-existing chronic health conditions, including CVD and diabetes.
Animal fluency tests consist of naming as many animals as possible in a short period of time, usually taking around a minute.
Underlying mechanisms
To explain their findings, the researchers noted that over the last few years, many studies have linked diets commonly rich in UPFs with cognitive dysfunction.
They wrote that underlying mechanisms might include systematic metabolic changes that lead to low-grade inflammation, impairment of the blood-brain barrier, and neuroinflammation.
They further noted that consuming high levels of UPFs may disrupt the microbiome and the gut-brain axis, as consuming them instead of whole foods may lead to a lack of essential nutrients and bioactive compounds with anti-inflammatory and antioxidant properties.
When asked what may explain the effects of UPF consumption on cognitive performance, Prof. Kaarin Anstey, scientia professor of psychology at the University of South Wales and senior principal research scientist at Neuroscience Research Australia (NeuRA), who was not involved in the study, told Medical News Today that UPFs, in theory, may worsen cognitive performance through several mechanisms.
“[U]nhealthy fats and sugars, which comprise [ultra-processed] foods, have independently been shown to impact brain health. [C]onsuming these foods [also] replaces the potential consumption of healthier foods which are more nutrient dense and associated with better cognitive health.”
— Prof. Kaarin Anstey
Prof. Antsey added that “UPF can increase obesity and type 2 diabetes, and both these conditions increase the risk of cognitive decline. In addition, the contribution of the many food additives in these foods to cognitive decline is not yet known.”
The researchers concluded that reducing UPF consumption may be a way to mitigate age-associated cognitive decline and reduce dementia risk.
Some limitations
When asked about the study’s limitations, one of the study’s authors Dr. Barbara Cardoso, senior lecturer in nutrition dietetics and food at Monash University, told MNT that causality can not be inferred from the study, as its participants were only assessed on one occasion.
As impaired cognition tends to develop over several years, a longer-term study would thus be necessary to draw stronger conclusions.
She further noted that 24-hour dietary recalls might not accurately represent usual dietary intake.
“Further, as we understand that people with chronic diseases are recommended to change dietary habits, it is possible that reverse causality could dilute the studied associations,” she said.
“The battery of cognitive tests was small, and it is possible that associations would have been found with other tests. […] Finally, while the study does sample different racial groups, there was a higher proportion of non-Hispanic whites in the sample and lower proportions of other racial groups than reflected in the general U.S. population,” Dr. Anstey also pointed out.
Despite the limitations, Dr. Cardoso noted that this is the first study to investigate the link between UPFs and cognitive decline and that it may pave the way for future research.
Optimal diet to prevent cognitive decline
When asked what people should eat more of to prevent cognitive decline, Dr. Cardoso said current research suggests a Mediterranean-style diet may have cognitive benefits.
“Research indicates that diets that follow a Mediterranean diet style, recognized by the high proportion of foods with anti-inflammatory and antioxidant properties, are associated with a reduced risk of age-associated cognitive decline and dementia. Foods consumed as part of these diets include fish, nuts, olive oil, and vegetables.”
— Dr. Barbara Cardoso
Dr. Anstey agreed with Dr. Cardoso and highlighted that a specific version of the Mediterranean diet known as the ‘MIND diet’ has been linked to a reduced risk of Alzheimer’s disease and dementia.
“The MIND diet emphasizes eating green leafy vegetables daily, nuts, as well as berries a couple of times per week,” she noted.
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