Could your diet be making your brain fog worse?

New research suggests that eating more ultra-processed food is associated with poorer attention and slower mental processing – even among people with otherwise healthy diets.

There are days when your brain just doesn’t seem to be working properly. You read a sentence and immediately forget it. Sometimes you walk into a room and can’t remember why. You struggle to find the right word, lose your train of thought or stare at your to-do list without knowing where to begin.

We often call it brain fog — that frustrating feeling of mental fuzziness, sluggishness or difficulty concentrating.

And we tend to look for someone or something to blame: too little sleep, too much stress, hormones. Frequently we blame our phones, too.

But what if part of the picture is on our plates?

New research suggests that eating more ultra-processed foods (UPFs) may be associated with poorer attention and slower mental processing. That could be the case even among people who otherwise eat a healthy diet.

Researchers from Monash University, the University of São Paulo and Deakin University analysed dietary and cognitive data from more than 2,100 middle-aged and older Australian adults who did not have dementia. Their findings, published in Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring, add to growing evidence that what we eat may influence how well our brains function.

A surprising link with focus

The researchers found that even relatively modest increases in ultra-processed food consumption were associated with measurable declines in attention and mental processing speed.

Lead author Dr Barbara Cardoso, from Monash University’s Department of Nutrition, Dietetics and the Victorian Heart Institute, puts the finding into everyday perspective:

“To put our findings in perspective, a 10 percent increase in UPFs is roughly equivalent to adding a standard packet of chips to your daily diet,” Dr Cardoso said.

“For every 10 percent increase in ultra-processed food a person consumed, we saw a distinct and measurable drop in a person’s ability to focus.

“In clinical terms, this translated to consistently lower scores on standardized cognitive tests measuring visual attention and processing speed.”

The participants were getting around 41 per cent of their daily calories from ultra-processed foods — almost exactly the Australian national average of 42 per cent.

That is significant because UPFs aren’t necessarily foods we think of as an occasional treat. They can be part of everyday life: packaged snacks, soft drinks, ready meals, biscuits and other products that have undergone extensive industrial processing.

It’s not just about eating an unhealthy diet

Perhaps the most intriguing finding was that the association between UPFs and poorer attention remained even among participants who generally followed a healthy, Mediterranean-style diet.

That suggests the issue may not simply be that people eating more UPFs are failing to eat enough nutritious food. The degree of processing itself could matter.

“Food ultra-processing often destroys the natural structure of food and introduces potentially harmful substances like artificial additives or processing chemicals,” Dr Cardoso said.

“These additives suggest the link between diet and cognitive function extends beyond just missing out on foods known as healthy, pointing to mechanisms linked to the degree of food processing itself.”

What does this mean for brain fog?

The study doesn’t prove that ultra-processed food causes brain fog. It was observational, meaning the researchers identified an association rather than establishing cause and effect. Nor did it find a direct link between UPFs and memory loss.

But attention is a fundamental part of cognition. We need it to learn, solve problems, follow conversations and take in information. If our ability to focus is compromised, it can affect how effectively we function throughout the day — and may contribute to that familiar sense of mental sluggishness we describe as brain fog.

The researchers also found that higher UPF consumption was associated with recognised dementia risk factors, including obesity and high blood pressure. Again, this doesn’t mean that eating processed food causes dementia, but it adds another reason to consider the potential long-term consequences of a heavily processed diet.

A gentler way to think about focus

None of this means we need to panic about the occasional packet of crisps, or eliminate every processed food.

Instead, the research offers an invitation to look at the bigger picture.

We often treat concentration as a matter of willpower: try harder, get organised, put the phone away. But perhaps focus is also something we support — through sleep, movement, rest, stress management and, potentially, the food we eat.

So if you’ve been feeling a little foggy lately, the answer may not be as simple as pushing yourself harder.

It might be worth looking at what’s on your plate, too.

Words: Lucy Rawlinson, Images: Shutterstock.