Could Your Diet Be Affecting Your Brain? New Harvard Research Links Ultra-Processed Foods to Dementia Risk
What if one of the biggest risk factors for cognitive decline isn't just aging, but what's on our plates?
A new study led by researchers at the Harvard T.H. Chan School of Public Health is adding to growing evidence that diets high in ultra-processed foods may significantly increase the risk of dementia and cognitive impairment. The findings are especially concerning because ultra-processed foods now make up an estimated 60% to 70% of the average American diet.
What the Study Found
Researchers followed more than 5,300 Americans aged 50 and older over nearly a decade. After accounting for factors such as age, education, smoking, physical activity, and alcohol use, they found that participants with the highest consumption of ultra-processed foods had:
58% higher risk of developing dementia
46% higher risk of developing cognitive impairment
Even moderate consumption was associated with increased risk compared with those who ate the least.
The good news? Participants who consumed the greatest amount of minimally processed foods—including fruits, vegetables, whole grains, fish, beans, and unprocessed meats—had substantially lower risks of cognitive decline.
What Are Ultra-Processed Foods?
Ultra-processed foods (UPFs) are industrially manufactured products that typically contain ingredients not found in a home kitchen, such as artificial flavorings, emulsifiers, preservatives, colorings, and high-fructose corn syrup.
Common examples include:
Sugary breakfast cereals
Packaged cookies and snack cakes
Potato chips
Hot dogs and processed deli meats
Soft drinks and energy drinks
Frozen ready-made meals
Instant noodles
Candy
While these foods are often convenient and inexpensive, they also tend to be high in added sugar, sodium, unhealthy fats, and additives while providing relatively little nutritional value.
Why Might They Affect the Brain?
Scientists are still investigating exactly why ultra-processed foods appear to be linked to poorer brain health, but several explanations are emerging.
These foods are associated with higher rates of obesity, Type 2 diabetes, cardiovascular disease, and high blood pressure—all established risk factors for dementia. Researchers also believe that chronic inflammation, changes to the gut microbiome, and certain food additives may contribute independently to declining cognitive health.
Importantly, this was an observational study, meaning it found an association rather than proving that ultra-processed foods directly cause dementia. Nevertheless, the findings are consistent with a growing body of research linking highly processed diets to poorer health outcomes, including heart disease, diabetes, depression, and earlier mortality.
What Can You Do?
No one needs to eliminate every processed food overnight. Small, sustainable changes can make a meaningful difference.
Public health experts recommend:
Eating more locally grown fruits and vegetables
Choosing whole grains over refined grains
Including beans, nuts, and legumes regularly
Selecting fresh or minimally processed proteins
Cooking at home more often, avoid fast food
Reading ingredient labels and limiting foods with long lists of additives
Replacing sugary drinks with water or unsweetened beverages
Rather than focusing on perfection, experts encourage gradually shifting the balance of your diet toward whole and minimally processed foods.
Brain Health Starts Long Before Old Age
Dementia is influenced by many factors, including genetics, education, physical activity, cardiovascular health, sleep, and diet. While no single food determines brain health, research increasingly suggests that the dietary choices we make throughout adulthood may have lasting effects on our cognitive well-being.
For New Hampshire families—and for communities everywhere—the message is simple: healthy eating isn't just good for the heart. It may also be one of the best investments we can make in protecting our brains as we age.