2026/05/18 Higher-Quality Plant-Based Diets Associated with Lower Dementia Risk in Large Multiethnic Study

A new study published in Neurology suggests that consuming a higher-quality plant-based diet may help reduce the risk of Alzheimer’s disease and related dementias (ADRDs), while diets rich in less healthy plant-based foods may increase dementia risk over time.
The study was conducted by researchers from the University of Hawaii at Manoa Cancer Center using data from the Multiethnic Cohort Study, one of the largest and most diverse long-term population studies in the United States. The analysis included 92,849 adults from Hawaii and California, including African American, Japanese American, Latino, Native Hawaiian, and White participants. At enrollment, participants were between 45 and 75 years old and were followed for more than a decade.
Researchers evaluated participants’ dietary habits using food frequency questionnaires and assessed three plant-based dietary patterns: an overall plant-based diet index (PDI), a healthful plant-based diet index (hPDI), and an unhealthful plant-based diet index (uPDI). Healthy plant-based foods included whole grains, fruits, vegetables, nuts, legumes, and vegetable oils, while unhealthy plant-based foods included refined grains, sugary foods, fruit juices, and heavily processed plant-based products.
During follow-up, more than 21,000 participants developed Alzheimer’s disease or related dementias. After accounting for age, physical activity, diabetes, and other health factors, researchers found that individuals with the highest adherence to overall plant-based diets had a 12% lower risk of dementia compared with those with the lowest adherence. Participants with the healthiest plant-based diets had a 7% lower risk, whereas those consuming the greatest amount of unhealthy plant-based foods had a 6% higher risk of dementia.
The study also examined long-term dietary changes among more than 45,000 participants who completed a second dietary assessment approximately 10 years later. Researchers observed that individuals whose diets shifted most strongly toward unhealthy plant-based eating patterns had a 25% higher risk of dementia. In contrast, participants who reduced their intake of unhealthy plant-based foods experienced an 11% lower risk.
Previous studies have shown that plant-based diets may help reduce the risk of chronic conditions such as diabetes and cardiovascular disease; however, evidence related to dementia prevention has been more limited. The current findings suggest that maintaining a higher-quality plant-based diet, while limiting unhealthy plant-based foods, may support cognitive health and lower dementia risk across diverse populations, regardless of age, racial or ethnic background, or APOE-ε4 genetic risk status.
 
https://www.neurology.org/doi/10.1212/WNL.0000000000214916