A long-term study found that healthier dietary patterns were associated with a lower risk of dementia among older adults.
The strongest findings were linked to diets with lower inflammatory potential, particularly in people with biological markers associated with Alzheimer's disease.
While the research cannot prove cause and effect, it suggests that healthy eating may remain an important part of brain health, even for those already at elevated risk.
What we eat has long been linked to overall health, but growing research suggests it may also play a role in keeping the brain healthy as we age.
A new study from researchers at the Karolinska Institutet in Sweden adds to that evidence, finding that older adults who more closely followed healthier eating patterns were less likely to develop dementia over time — even if blood tests indicated they were already at increased biological risk for Alzheimer's disease.
The findings are especially notable because many dementia prevention studies focus on the general population. This research instead examined whether diet might still make a difference among people with elevated levels of biomarkers linked to Alzheimer's disease and other forms of neurodegeneration.
Researchers found that the most consistent benefits were associated with dietary patterns that have lower inflammatory potential, suggesting that reducing inflammation through diet may be one piece of the puzzle for maintaining brain health.
"Our findings suggest that diet quality, and particularly dietary patterns with inflammatory potential, may be relevant for dementia prevention in people who already show biological signs of increased risk," corresponding author Anja Mrhar, Ph.D. student from University of Ljubljana, Slovenia, said in a news release.
How the researchers studied the connection
The study followed 1,865 adults in Sweden who were at least 60 years old and did not have dementia when the research began. Participants were followed for an average of 8.4 years, with some tracked for nearly 16 years. During that time, 240 participants developed dementia.
Researchers evaluated participants' eating habits using three well-established measures of diet quality: the Alternate Mediterranean Diet (AMED), the Alternative Healthy Eating Index (AHEI), and the reversed Empirical Dietary Inflammatory Index (rEDII), which estimates how inflammatory a person's diet may be.
Blood samples were also analyzed for biomarkers associated with Alzheimer's disease and broader neurodegenerative processes, including phosphorylated tau (p-tau217), neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP). The researchers then examined whether diet quality influenced dementia risk across different levels of these biomarkers.
What the findings mean for consumers
Overall, the researchers found that healthier diets were associated with a lower risk of developing dementia.
The clearest and most consistent results involved dietary patterns with lower inflammatory potential. Among participants with elevated biomarker levels, greater adherence to a less inflammatory diet was linked to a lower risk of dementia, with some groups experiencing up to about a 30% lower relative risk compared with those whose diets were more inflammatory.
The study was observational, meaning it cannot prove that diet directly prevents dementia. However, the findings suggest that healthy eating may still be beneficial even for older adults who already have biological signs associated with Alzheimer's disease.
According to the researchers, these results support the idea that diet could remain an important part of strategies aimed at reducing dementia risk, while reinforcing the need for additional research to better understand the relationship.
"These findings move us closer to precision nutrition, suggesting that different dietary patterns may be particularly beneficial for different groups of older adults," researcher Adrián Carballo-Casla said in the news release.