A new study links ultra-processed food consumption to brain changes that may increase the risk of stroke and memory problems later in life.
Ultra-processed food has been tied, study after study, to extra body fat, diabetes and heart disease. What it does to the brain has been far less clear. A new set of brain scans suggests the brain belongs on that list too, well before old age.
The heaviest eaters of packaged snacks, sugary cereal, soft drinks and ready meals were about 40% more likely to have small patches of damaged tissue in the brain. These were healthy adults between 35 and 69 with no symptoms, and their memory and thinking scores matched everyone else’s.
Russell de Souza, an associate scientist at the Population Health Research Institute in Hamilton, Ontario, led the study with Sonia Anand. The institute is run jointly by McMaster University and Hamilton Health Sciences. Researchers measured everyone once, so they could identify a connection between diet and brain damage but could not establish whether one caused the other.
“I would not have expected this finding, frankly. We studied middle-aged Canadians who had no heart problems and reported no other health concerns,” de Souza said. “Usually, this kind of damage is associated with conditions we hear about and treat at a much older age.”
Ultra-processed foods linked to brain damage
The team used scans and diet records from 8,783 adults across Canada with no history of heart disease. All of them had joined one of two long-running health projects. One was the Canadian Alliance for Healthy Hearts and Minds, and the other was the Canadian part of PURE-MIND, a brain study inside the global PURE project.
Each participant had filled out a questionnaire about what they ate over the previous year. Neurologists who knew nothing about anyone’s diet then read the brain scans.
They were looking for two things: small strokes that had happened without anyone noticing, and damaged patches in the brain’s wiring, the white matter. Either one counted as damage.
About 9% of the whole group had it. Among the quarter who ate the least ultra-processed food, 8.1% did. Among the quarter who ate the most, 11.3% did. The gap held after the researchers accounted for age, income, smoking, exercise, and existing conditions like high blood pressure and diabetes.
Brain damage goes beyond abdominal fat
The heaviest eaters also carried more belly fat. Their body fat ran about 1.7 percentage points higher than the lightest eaters’. The fat packed deep inside the abdomen, around the organs, measured about 0.2 fluid ounces (5.7 milliliters) more on their scans, a little over a teaspoon. Fat in the liver did not differ.
The pattern was strongest in people with obesity, and it didn’t appear at all in people of normal weight.
Researchers suspect deep abdominal fat may help explain the connection between diet and brain health because it contributes to inflammation and blood vessel damage. Yet when they included fat measurements in their calculations, the link barely changed, suggesting that something about the food itself may also play a role.
Brain damage appears without memory loss
Every participant took two short tests of memory, attention and processing speed. The heaviest eaters scored the same as the lightest.
The group as a whole scored high, which may have left the tests little room to show a difference. The researchers also said brief tests like these may not be sensitive enough to catch early changes in a middle-aged brain.
Anand, the study’s senior author, put it this way.
“Our findings suggest that the link between diet and brain health may be detectable before people experience noticeable problems with memory or thinking,” Anand said. “This adds to the growing evidence that what Canadians eat in their 30s, 40s, 50s, and 60s shapes their brain health later in life.”
Brain damage link emerges mainly in women
When the researchers compared men and women, they found that the link between diet and brain damage was strongest in women.
Women who ate the most ultra-processed food had about 1.8 times the odds of silent brain damage compared with those who ate the least. The researchers compared the highest and lowest quarters of food consumption. For men, the two groups looked the same.
The researchers did not plan these comparisons in advance and called them exploratory. Possible reasons, such as hormones, could not be tested here.
Packaged foods take up more of the diet
In the top quarter, ultra-processed items made up 45% of everything eaten, counted by servings. In the bottom quarter they made up 16.5%. Fresh and minimally processed foods, such as fruit, vegetables, and grains, showed the opposite pattern. They accounted for 68.6% of servings among those who ate the least ultra-processed food, compared with 41.5% among those who ate the most.
The heaviest eaters weren’t eating fewer vegetables, though. They ate slightly more vegetables, whole grains, and dairy each day. They also consumed about 300 more calories overall. But as a share of the plate, everything else shrank.
“People who ate more ultra-processed foods weren’t simply eating more on top of their usual diet. These foods appeared to crowd out healthier whole foods,” de Souza said.
The heaviest eaters were also more likely to have lower incomes and less schooling.
“For many Canadians, ultra-processed food is often a convenient and affordable option. But our findings suggest that diets high in these foods may be linked to brain changes that may lead to memory loss and stroke as Canadians grow older,” Anand said.
Can changing diets protect brain health?
Everything in this study was measured at one visit, and the diet questionnaire covered one year, while damage of this kind likely builds over far longer.
The researchers also found that the brain result depended on how they counted intake. Measured as servings per 2,000 calories, it held. Measured as a share of total calories or of total servings, it faded, which they said is a reason for caution.
Whether cutting back on ultra-processed food would change what shows up on a scan is the question this study can’t answer.
“We need longer-term studies that track people over time with repeated MRI scans to find out whether reducing ultra-processed food intake can slow or prevent these brain changes,” de Souza said. “Such follow-up is ongoing.”
Repeat scans of the same people could show whether the damage gets worse over time, and whether it tracks with what they eat.
The full study was published in the journal JAMA Network Open.
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