Junk food may be giving us brain damage, from ‘silent strokes’ to higher dementia risk

From hot dogs to soft drinks, white bread to sugar cereals, ultraprocessed foods have saturated the modern diet like grease through a paper takeout bag.

We know these foods aren’t particularly nutritious, but a growing body of evidence suggests they may be damaging our brains. Studies have linked ultraprocessed foods with heightened dementia risk, diminished cognitive function and even what’s known as “silent strokes.”

“There are many, many studies now,” said Dr. Sonia Anand, a professor of medicine and epidemiology at McMaster University. In October, she and her team published a paper linking ultraprocessed food consumption with vascular brain injury. “There are huge population implications.”

Today, the average Canadian gets nearly half their daily calories from such foods, whose ingredient lists often include difficult-to-pronounce additives and are high in sugars, fats and sodium but lacking in vitamins, minerals, fibre and other nutrients.

That may not be by choice. Ultraprocessed foods are often cheap, easily accessible and require minimal preparation. For a growing number of Torontonians facing food insecurity, who may be limited in money, time and access to a kitchen, these foods are the only option.

A new report from Daily Bread published Tuesday morning found Toronto food bank visits have soared 333 per cent since 2019, with 4.1 million visits logged from April 1, 2025 to March 31, 2026.

“They simply do not have the funds to move away from ultraprocessed foods,” said Neil Hetherington, CEO of Daily Bread. “The average food bank user has about $8.33 per day to pay for everything, after they’ve paid for rent.”

The U of T study found that nearly one in five of the more than 2,000 children they followed over a five-year-long study was overweight by age five.

The U of T study found that nearly one in five of the more than 2,000 children they followed over a five-year-long study was overweight by age five.

One in eight children in Toronto now rely on food banks — nearly double the rate in 2022. Some experts worry about what this could mean for kids’ development, as ultraprocessed foods have been linked with ADHD in children and may rewire their reward pathways.

Here’s what you need to know.

Will junk food give you brain damage?

Anand and her team at McMaster scanned the brains of more than 8,700 Canadians with no history of heart disease, and found those who consumed the most processed food were 40 per cent more likely to show signs of “silent strokes” — tiny spots of damage that produce no obvious symptoms, but may contribute to neurological issues later in life.

“We see an area of the brain tissue that has basically died,” Anand said. “The more you have of those, the lower your cognitive abilities — or abilities to think well. And it’s an early sign that an individual is at risk of a future clinical stroke and dementia.”

Participants who ate the most ultraprocessed foods — consisting of 45 per cent of their daily food servings — were nearly twice as likely to show signs of brain injury than those who ate the least, about 16 per cent of their daily servings.

Whether they know it or not, most Americans don’t go a day — or often a single meal — without eating ultraprocessed foods.

Whether they know it or not, most Americans don’t go a day — or often a single meal — without eating ultraprocessed foods.

In comparison, the average Canadian gets about 46 per cent of their daily calories from ultraprocessed foods, according to the 2015 Canadian Community Health Survey.

In recent years, researchers have linked higher ultraprocessed food consumption with deficits in memory, executive function and overall cognition.

In 2022, a major longitudinal study of more than 10,000 individuals over eight years linked high consumption of ultraprocessed foods with a 28 per cent faster rate of cognitive decline and a 25 per cent faster decline in executive functioning. That same year, another paper found that increasing our consumption of these foods by 10 per cent was linked to a 25 per cent higher dementia risk.

What exactly are ultraprocessed foods?

Not all ultraprocessed foods are equally unhealthy. They are classified based on their level of processing, not their nutritional quality or biological effects, noted Sara Mahdavi, a registered dietitian and adjunct professor of nutritional sciences at the University of Toronto.

“Emerging research suggests that specific (ultraprocessed food) categories, rather than total consumption alone, may be driving some associations,” she said. “We need to understand whether the risk comes from nutritional composition, industrial additives, altered food structure or the healthier foods being displaced.”

Evidence suggests it’s not just a lack of nutrients that’s leading to these results. Studies that accounted for nutritional differences between ultraprocessed and whole foods arrived at the same conclusion, said Anthea Christoforou, an assistant professor of nutritional epidemiology and food policy at McMaster. “What else is in these foods that’s causing this problem?”

MONTREAL - Children in Canada are exposed to more than 4,000 ads for food on their mobile devices every year, with the vast majority promoting…

MONTREAL - Children in Canada are exposed to more than 4,000 ads for food on their mobile devices every year, with the vast majority promoting…

In her research, Christoforou found Canadians who ate more ultraprocessed foods displayed more markers of inflammation. “That suggests something in these foods may be prompting a low-grade inflammatory response, almost as if the body is treating some of their components less like food and more like something foreign,” she said. “We still need to pin down what’s driving that, but additives and processing-related changes are strong candidates.”

Food additives like bisphenol A, tartrazine and erythrosine have been linked to hormonal disruption and gut inflammation. Ultraprocessed foods may also contain potentially harmful contaminants from packaging materials, such as bisphenols, phthalates or microplastics.

The price of healthy food

Food insecurity is a deepening problem as Canada’s cost of living continues to rise, and experts say its root causes should be addressed.

“We need to make sure there’s affordable housing built, and that people on fixed incomes like disability have an income that is at least at the poverty line,” Hetherington said. “We’re also seeing a rise in precarious employment, which means a rise in food-insecure Canadians.”

The government could provide subsidies to make healthy foods more affordable while raising taxes on junk foods, Anand suggested. It could restrict the marketing of these foods to children. And it could improve labelling, like California’s recent move to prominently label non-ultraprocessed foods.

Health Canada’s recent move to introduce front-of-package labelling on foods high in saturated fats, sugar or sodium is a good step forward, experts say, but more can be done. Canada’s food guide, which serves as the basis for much of the nation’s food procurement policies, could take a harder stance against ultraprocessed foods — like introducing national targets to reduce our consumption, said Christoforou.

“The education is helpful, but it’s only helpful for somebody who has choice,” Hetherington said. “What I see every single day at the food banks across the city of Toronto is that these individuals don’t have choice.”