A large multiethnic cohort followed for about 11 years evaluated how quality of plant-based diets relates to dementia risk. Researchers assigned participants to five subgroups by plant-based diet scores, distinguishing overall plant food intake from healthful versus unhealthful plant components.
Across the full follow-up, the highest plant-diet quality group—those consuming the most plant foods and prioritizing healthful plant options—showed a 12% lower risk of dementia than the lowest group. When focusing on diet healthfulness, the top subgroup had a 7% lower dementia risk, while the lowest subgroup consuming the most unhealthy plant foods had a 6% higher risk.
In a subset followed for 10 years, shifts toward an unhealthy plant-based diet increased dementia risk by 25%, whereas adopting a less unhealthy plant-based pattern reduced risk by 11%. The effects were similar for individuals younger and older than 60 at baseline, suggesting potential dementia-related benefits from dietary changes later in life.
Uncertainty remains regarding causality and broader applicability beyond the study population, and exact mechanisms were not delineated in the reported data.
Quality Plant-Driven Patterns and Dementia Risk: Evidence from a Longitudinal, Multiethnic Cohort
The central question is whether the quality of plant-based eating—distinguishing healthful from unhealthful plant foods—modifies later dementia risk, and whether dietary improvements later in life can alter risk trajectories.
Nearly 93,000 adult participants with a mean age around 59 at baseline were recruited.
The cohort encompassed diverse racial and ethnic groups, including Caucasian, African American, Japanese American, Native Hawaiian, and Latino participants.
Participants were followed for an average of 11 years, with a subset extended to roughly 10 years for evaluating changes in diet over time.
A healthful plant-based diet emphasizes vegetables, fruits, whole grains, legumes, nuts, and seeds, with little or no animal protein.
In contrast, an unhealthful plant-based pattern is characterized by higher intake of ultra-processed plant foods, fried items, and foods high in added sugars and salt.
Additional analyses focused on dietary changes over time within a subset of participants.
This signal suggests that higher quantities of plant foods correlate with reduced dementia risk.
This indicates that unhealthy plant-based choices may offset potential benefits from plant-based eating.
Participants who shifted toward a less healthy plant-based pattern experienced a 25% increase in dementia risk over the observation period.
This finding suggests that making dietary improvements later in life may still impart measurable benefits for brain health.
The findings align with the notion that plant-forward patterns can influence brain aging, but emphasize that quality of plant foods matters, not merely the presence of plant-based components.
Residual confounding cannot be ruled out.
The report notes uncertainty about how broadly these findings apply outside the studied groups.