What Brain Scans Revealed About Ultra-Processed Foods

Think about an ordinary week of groceries, with a bag of chips, a box of sweet cereal, a few flavoured yogurt cups, and a frozen dinner for the night you are too tired to cook. A new study from McMaster University suggests that years of eating this way may leave marks on the brain that you would never feel, the kind that only an MRI can see.

Researchers scanned the brains of nearly 9,000 healthy Canadians between the ages of 35 and 69. The people who ate the most ultra-processed foods were about 40 percent more likely to show tiny areas of damage. The study shows a link rather than proof that the food caused it, and a follow-up that scans the same people again is already underway.

Key takeaways

In a McMaster University study of nearly 9,000 Canadians aged 35 to 69, the heaviest eaters of ultra-processed food were about 40 percent more likely to show silent damage on a brain MRI.

For the heaviest eaters, ultra-processed food made up about 45 percent of daily servings, compared with 16 percent for the lightest eaters.

The damage causes no symptoms, though doctors treat it as an early warning sign for stroke and memory problems later in life.

Researchers scanned each person once, so the study cannot prove the food caused the damage, and results from repeat scans should arrive in early 2028.

Budget-friendly swaps, such as plain yogurt with fruit or oats instead of sugary cereal, move a diet in the right direction.

What did nearly 9,000 brain scans actually show?

The research comes from a Canada-wide project that began in 2014 and enrolled middle-aged adults with no history of heart disease. As CTV News reported on October 15, every participant filled out a detailed food questionnaire and had an MRI, and the brain scans were read by neurologists who did not know what anyone ate.

The findings, published in JAMA Network Open the same day, compared the people who ate the most ultra-processed food with those who ate the least. The top group was about 40 percent more likely to show what researchers call vascular brain injury, which is damage tied to the small blood vessels that feed the brain. The link looked stronger in women, who in the top group were nearly twice as likely to show these changes.

The heaviest eaters got close to half of their daily servings from ultra-processed food, and whole foods shrank to make room.

Which packaged foods count as ultra-processed?

Ultra-processed foods are the heavily manufactured products that fill the middle aisles of the grocery store, built mostly from refined ingredients and additives you would rarely keep at home. Russell de Souza, the study's first author and a registered dietitian at McMaster, points to chips, sweet breakfast cereals, highly processed sweetened yogurts, and some frozen meals as everyday examples.

McMaster's announcement of the findings adds soft drinks, instant noodles, and packaged snack foods to the list. Plenty of packaged foods are perfectly ordinary, though, since a bag of frozen peas or a can of chickpeas has been processed without becoming ultra-processed. What matters is how far the food has travelled from something you would recognize as a plant or an animal.

What does a silent brain injury actually mean?

A silent brain injury is a small patch of damaged tissue that causes no symptoms at all, so a person can live with one for years without knowing. Dr. Sonia Anand, the study's senior author, told CTV News that the team found a mix of silent strokes and what she called a pre-stroke profile in some participants whose diets were more than 45 percent ultra-processed.

These changes matter because doctors treat them as early warning signs that can appear years before a stroke or memory problems begin. That is why researchers pay attention to them in people who otherwise feel healthy. The heaviest eaters in the study also carried more body fat, including more of the deep belly fat that researchers link to inflammation and blood vessel damage. If your own memory is already on your mind, the 10-minute memory test every adult should take is a simple place to start.

Can one study prove cause and effect?

Anand believes the food itself is responsible, telling CTV News that the team observed an independent effect of ultra-processed food on the damage seen in the scans. Even so, the study looked at each person only once, so it can show that heavy consumption and brain damage tend to travel together without proving cause and effect.

That gap is the reason for the next phase of the research. Some participants who volunteered six or eight years ago are now coming back for a second MRI. Those scans will let researchers track how each brain changes alongside the person's diet, with results expected in early 2028. The findings also fit earlier research on how what you eat could affect your memory even after early warning signs appear.

How common is a heavily processed diet in Canada?

The most uncomfortable part of this study may be how ordinary the high-risk group's eating looks. In 2025, the Heart and Stroke Foundation reported that nearly half of the food the average Canadian eats each day is ultra-processed, which puts a heavily processed diet close to the national norm.

None of this means a single bag of chips will harm your brain. What the study adds is a new kind of evidence, drawn from real brain scans of Canadians. It suggests that the overall pattern of what you eat across decades may matter for your brain as well as your heart and your waistline. Diet is one of several levers you control, and our guide to the risk factors for memory loss you can actually change covers the rest.

The researchers are honest about the catch, too. De Souza noted that with food prices where they are, affording whole-food meals is out of reach for some individuals and families, so eating better is far more complicated than a question of willpower.

What can you change on a tight grocery budget?

You do not need to overhaul your kitchen to make a start. De Souza's own advice is practical: eat at home as much as you can, buy local, and watch for sales at the supermarket, and every step below works on a normal grocery budget.

Swap the sweetened yogurt. Plain yogurt with fruit gives you the same creaminess without the added sugar and flavourings of a sweetened cup.

Trade sugary cereal for oats. Plain oats are usually cheaper per bowl and keep you full longer than most sweet breakfast cereals.

Batch-cook one meal a week. A pot of soup or chili portioned into the freezer can stand in for a few frozen dinners.

Read the ingredient list. A long list of ingredients you would never find in a home kitchen is a good sign that a product is heavily processed.

Change one thing at a time. Pick one or two swaps that fit your budget and your week, and add more once they feel normal.

Each swap keeps most of the convenience and drops much of the processing.

Frequently asked questions

Can ultra-processed food damage your brain?

A McMaster University study of nearly 9,000 Canadians found that people who ate the most ultra-processed foods were about 40 percent more likely to show silent damage on brain MRI scans. The study shows a link and cannot prove that the food caused the damage. Repeat scans of the same people, expected in early 2028, should help answer that question.

What counts as an ultra-processed food?

Ultra-processed food is made mostly from refined ingredients and additives you would rarely use at home, such as preservatives, sweeteners, and flavourings. Common examples include chips, sweet breakfast cereals, sweetened yogurts, soft drinks, instant noodles, and many frozen meals. Frozen vegetables, canned beans, and plain yogurt are processed too, although they stay much closer to the original food.

What is a silent brain injury?

A silent brain injury is a small area of damaged brain tissue that causes no noticeable symptoms, usually linked to problems in the tiny blood vessels that supply the brain. It is typically found only on an MRI done for another reason. Doctors treat these changes as early warning signs, because they can appear years before a stroke or memory problems.

How can I eat less processed food on a budget?

Cooking at home more often, buying local, and shopping the weekly sales are the steps the study's co-author recommends. Simple swaps help as well, such as plain yogurt with fruit instead of sweetened cups, oats instead of sugary cereal, and batch-cooked soup in place of some frozen dinners. A registered dietitian can build a plan around your budget.

Your next step

If you want help eating less processed food without blowing your grocery budget, a registered dietitian can build a plan around how you actually shop and cook. The Medimap Health Hub has more on food and brain health, and you can find and book a dietitian near you on Medimap.

Disclaimer: This article is for general information only and is not medical advice. It does not replace a conversation with a doctor or other qualified health professional who knows your history. If you think you are having a medical emergency, call 911 or go to the nearest emergency department.