Summary: It’s not enough to simply eat more plants — the type of plant foods matters. A large, long-term study following nearly 93,000 people for about 11 years examined how different plant-based diets relate to the risk of Alzheimer’s disease and other dementias.
Researchers found that higher overall plant intake was linked with lower dementia risk, but diets that emphasized low-quality plant foods — refined grains, potatoes, fruit juices and added sugars — were associated with a greater risk. The findings indicate that moving toward a higher-quality plant-based diet, even in middle age or later, may meaningfully protect brain health over time.
Key Facts
- Healthful plant-based diet benefit: Participants scoring highest for a healthful plant-based diet had a 7% lower risk of dementia compared with those scoring lowest.
- Unhealthful plant-based diet risk: Participants who ate the most unhealthy plant foods showed a 6% higher risk of dementia.
- Diet changes matter: Among people whose diets changed over a decade, those who shifted away from unhealthy plant foods reduced their risk by 11%, while shifts toward unhealthy plant patterns increased risk by 25%.
- Later-life benefit: The average age at the start was 59, showing that dietary improvements in middle age and beyond can still provide measurable protection.
- Diverse study population: The study included African American, Japanese American, Latino, Native Hawaiian and white participants, improving the relevance of findings across groups.
Source: AAN
Overview
Published April 8, 2026 in Neurology, this observational study links higher-quality plant-based eating patterns with a lower risk of Alzheimer’s disease and related dementias. Because it is observational, the research demonstrates association, not proof of cause and effect.
Investigators evaluated three plant-based diet patterns: an overall plant-based diet that emphasizes eating more plant foods than animal products without distinguishing quality; a healthful plant-based diet that prioritizes whole grains, fruits, vegetables, vegetable oils, nuts, legumes, tea and coffee; and an unhealthful plant-based diet defined by refined grains, fruit juices, potatoes and added sugars. The study did not specifically assess vegetarian or vegan diets.
Lead author Song-Yi Park, PhD, of the University of Hawaii at Manoa’s Cancer Center, noted that while plant-based patterns are known to help prevent conditions such as diabetes and high blood pressure, their relationship to Alzheimer’s and other dementias has been less clear. This analysis shows that diet quality within plant-based patterns is a key factor linked with dementia risk.
The cohort included 92,849 adults who averaged 59 years old at baseline and represented multiple racial and ethnic groups. Participants completed food-frequency questionnaires at the start, and researchers scored each person on the three plant-based diet indexes based on consumption of healthy and less healthy plant foods and of animal products. Scores for each index were divided into five groups for analysis.
Over an average follow-up of 11 years, 21,478 participants developed Alzheimer’s disease or related dementia. After adjusting for age, physical activity, diabetes and other relevant factors, the group with the highest overall plant-based diet score had a 12% lower risk of dementia compared with the lowest group. For the healthful plant-based diet index, the highest-scoring group had a 7% lower risk. For the unhealthful plant-based diet index, the highest-scoring group experienced a 6% higher risk.
A subset of 45,065 participants repeated dietary questionnaires after about 10 years; among them, 8,360 later developed dementia. Analysis of dietary change found that people who moved most toward unhealthy plant-based eating faced a 25% higher dementia risk, whereas those who moved away from unhealthy plant patterns reduced their risk by 11% compared with people whose diets remained stable.
The authors emphasize that adopting a higher-quality plant-based diet, even when started later in life, was associated with reduced dementia risk. At the same time, diets high in refined carbohydrates and added sugars may raise the risk.
Study limitations include reliance on self-reported food questionnaires, which can introduce recall error. The analysis adjusted for multiple confounders, but residual confounding is possible.
Funding: Supported by the National Institute on Aging and the National Cancer Institute at the National Institutes of Health.
Key Questions Answered:
A: The study suggests that an unhealthful plant-based pattern—heavy in refined grains, potatoes and added sugars—was linked with a higher dementia risk. Eating plant-based helps brain health when the emphasis is on whole, nutrient-dense foods rather than processed or high-sugar plant items.
A: No. Participants who shifted their diets toward healthier plant-based patterns later in life showed a measurable reduction in dementia risk, indicating that dietary changes in middle age and beyond can still provide benefits.
A: The study reports an association. Other research suggests refined carbohydrates and sugars can contribute to blood sugar spikes, metabolic stress and inflammation, which may negatively affect brain health over time.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context provided by staff.
About this exercise and neuroscience research news
Author: Renee Tessman
Source: AAN
Contact: Renee Tessman – AAN
Image: Image credited to Neuroscience News
Original Research: Findings published in Neurology