Ultraprocessed foods contain little, if any, whole foods and are typically high in calories, fatty, salty, sugary and contain numerous additives.Yulia337/Getty Images/iStockphoto
An enormous amount of evidence has linked ultraprocessed foods to an increased risk of many chronic diseases, including hypertension, coronary heart disease, Type 2 diabetes, obesity and depression.
More recently, though, research has raised concerns about the harmful effects of ultraprocessed foods on brain health.
Several studies have tied these foods to poorer cognitive performance and accelerated cognitive decline.
Now, new research published April 23 suggests that higher daily intakes of ultraprocessed food – even a small amount– can worsen thinking skills and increase dementia risk.
Here’s what to know about the latest study.
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What are ultraprocessed foods?
Ultraprocessed foods (UPFs) are formulations of ingredients, typically made by deconstructing whole foods, altering and recombining them with additives to flavour, sweeten, bleach, colour, emulsify, texturize and preserve. They contain little, if any, whole food.
The processing of UPFs strips away vitamins, minerals, fibre and protective phytochemicals while, at the same time, adding unhealthy fats, added sugars and sodium.
The Nova food classification system, introduced in 2009, categorizes foods based on their level of processing from group 1 (least processed) to group 4 (most processed).
The top contributors to Canadian’s ultraprocessed food intake are sugar-sweetened drinks, packaged snacks (chips, crackers, pretzels) and baked goods (cookies, cakes, pastries), sweetened breakfast cereals and desserts, ready-to-eat or ready-to-heat meals and processed meats.
The new research
The study, published in the journal Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, investigated the association of ultraprocessed food consumption with cognitive performance and dementia risk.
The researchers examined the diets and cognitive health of 2,192 Australian adults, aged 40 to 70, who were free of dementia.
Participants’ diets over the previous 12 months were assessed and their intake of UPFs was classified using the Nova system. The researchers also calculated their Mediterranean diet scores to account for overall diet quality.
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Participants underwent cognitive testing to measure processing speed (how fast the brain works when doing a mental task) and visual attention (the brain’s ability to focus on and quickly respond to what you see). Together, these scores were used to generate an overall attention score. A separate memory score was also determined.
Researchers used a validated risk score to estimate participants’ likelihood of developing dementia later in life, based on age, sex, education, blood pressure, blood cholesterol, body weight and physical activity.
They also looked specifically at the modifiable components of this score – blood pressure, cholesterol, weight, physical activity – to better understand how diet might influence aspects of dementia risk that are within a person’s control.
Small daily increase in UPFs linked to poorer attention
Participants consumed, on average, 41 per cent of their daily calories from ultraprocessed foods – similar to Canadian adults (about 44 per cent).
The most commonly consumed ultraprocessed foods were dairy-based desserts, sugar‑sweetened beverages, packaged salty snacks and potato products, processed meats and ready‑to‑heat meals.
For every 10 per cent increase in ultraprocessed foods – roughly 150 grams per day, about a small bag of potato chips – participants had consistently lower scores on cognitive tests measuring attention.
A higher intake of UPFs was also linked to a higher dementia risk score, largely explained by modifiable risk factors such as blood pressure, cholesterol, body weight and physical activity.
This finding underscores the importance of maintaining metabolic health to protect brain health.
Notably, these associations persisted regardless of overall diet quality (Mediterranean diet score), suggesting that the degree of food processing – not just lower intakes of beneficial nutrients – may play a role in cognitive decline.
No association was found between ultraprocessed food intake and memory.
Because attention is central to cognitive functions such as learning, problem solving and memory, the researchers speculated that early changes in attention may precede broader cognitive decline.
Strengths, limitations
The study’s strengths include its large sample size and use of validated cognitive testing.
As well, the researchers adjusted for overall diet quality, which helps distinguish the effects of food processing itself from simply having a less healthy diet overall.
However, the study looked at diet and cognition at a single point in time and relied on self‑reported diet information.
As a result, it found an association between UPFs and cognition; it didn’t prove that UPFs directly affect brain health.
Still, the new findings add to growing evidence that diets higher in UPFs are linked to poorer cognitive performance, even after accounting for overall diet quality.
How UPFs may harm brain health
There are several plausible ways these foods may affect cognition.
The loss of beneficial nutrients and phytochemicals in UPFs, along with the addition of potentially harmful additives, may promote inflammation and other processes that could affect brain health.
UPFs are also linked to a higher risk of hypertension, elevated blood cholesterol, obesity and Type 2 diabetes, key contributors to dementia risk.
As well, some additives in UPFs may disrupt the gut microbiome, possibly weakening the gut barrier and allowing inflammatory substances to enter the bloodstream which, over time, could affect brain function.
What to do?
It’s impossible to completely avoid UPFs.
The goal, instead, is to limit their consumption by eating more whole and minimally processed foods.
Gradually replace ultraprocessed foods with real ones.
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan.
