Harvard Study Links Ultra-Processed Foods to 58 Percent Higher Dementia Risk in Older Adults
A Harvard study published in the American Journal of Public Health found that older adults with the highest intake of ultra-processed foods had a 58 percent higher risk of developing dementia and a 46 percent higher risk of cognitive impairment. Those who ate the most whole foods had a 41 percent lower dementia risk.
Older adults who eat the most ultra-processed foods have a 58 percent higher risk of developing dementia and a 46 percent higher risk of cognitive impairment without dementia, according to a study published June 3, 2026, in the American Journal of Public Health.
Harvard researchers analyzed data from 5,370 older adults with an average age of 64, following them for nearly nine years. The study found a clear pattern: higher consumption of ultra-processed foods was tied to worse cognitive outcomes, while higher intake of whole, minimally processed foods was tied to better ones.
People with the highest intake of whole foods had a 41 percent lower risk of dementia and a 24 percent lower risk of cognitive impairment without dementia compared to those who ate the least whole foods.
Researchers say ultra-processed foods may affect the brain through several pathways. High levels of refined sugars, additives, and saturated fats can promote systemic inflammation and oxidative stress, which are linked to neurodegeneration. These foods are also tied to obesity, hypertension, diabetes, and high cholesterol, all established risk factors for cognitive decline.
Some researchers also point to the gut-brain axis, suggesting that ultra-processed foods may alter gut bacteria in ways that promote neuroinflammation.
A separate study of Dutch older adults published in the European Journal of Nutrition in February 2026 found no association between ultra-processed food intake and cognitive decline over 10 years, highlighting that findings in this area remain mixed across different populations.
Experts say the overall body of evidence supports reducing ultra-processed food consumption as part of a strategy to protect brain health.
