By naturopath Margaret Jasinska

A new study has found high consumption of ultra processed food is associated with poor attention and an elevated risk for dementia in middle aged and older adults. Interestingly the association remained strong even after adjusting for adherence to a Mediterranean diet. Eating junk food harms your brain even if you also eat healthy food as well.

Researchers studied nearly 2,200 Australian adults between the ages of 40 and 70 (average age 57). None had dementia at the start of the study, and participants were recruited as part of the Healthy Brain Project from 2016 to 2023. Most participants were women (75%).

To understand what people were eating, participants completed a detailed food survey covering 130 different foods and drinks, describing their typical eating habits over the past year. The research team used these responses to score how closely each person followed a Mediterranean diet — an eating pattern rich in fruits, vegetables, whole grains, fish, and healthy fats.

Participants also completed a series of computerized cognitive tests measuring things like how quickly they could process information, how well they paid attention to visual details, and how effectively they could hold and use information in short-term memory. These scores were combined into two broader measures: an attention score and a memory score.

Finally, the researchers estimated each person’s risk of developing dementia later in life using an established tool that factors in cardiovascular health and ageing.

To make sure the results were as accurate as possible, the team accounted for other factors that could influence brain health, including age, gender, exercise habits, smoking, and any history of heart or metabolic conditions like diabetes. In the most detailed version of their analysis, they also factored in body weight (BMI) and how closely someone followed the Mediterranean diet.

What the research found: ultra-processed foods and brain health

Researchers looked at how eating ultra processed foods; things like packaged snacks, ready meals, and factory-made drinks affects the brain as we age. Here’s what they discovered:

The most commonly eaten ultra processed foods were dairy-based sweet treats and drinks (flavoured yoghurts and milkshakes), followed by soft drinks, fruit-flavoured beverages, and other sugary drinks.

Higher ultra processed food consumption was linked to a greater risk of dementia. People who ate more junk food had higher scores on a scale used to measure dementia risk, and this held true even among people who otherwise followed a healthy Mediterranean-style diet.

So that means the vegetables you eat for dinner are not going to undo the junk food you snacked on throughout the day.

Eating more junk food was also linked to worse attention. For every 10% increase in the proportion of ultra processed foods in someone’s diet, their ability to focus and pay attention dipped measurably. People whose diet was made up of more than 28% junk food by weight had noticeably worse attention than those who kept these foods below 13% and this was true regardless of how healthy the rest of their diet was.

Cutting back on ultra processed foods may be worth considering for long-term brain health.

According to the lead author of the study, “to put our findings in perspective, a 10% increase in ultra processed foods is roughly equivalent to adding a standard packet of chips to your daily diet. For every 10% increase in junk 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”.

There is a lot you can do to improve your brain health. The brain damage of dementia usually starts in a person’s 40s. Learn how you can protect your brain in Dr Cabot’s book Alzheimer’s: What you must know to protect your brain.

Reference: https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/dad2.70335