A study published on April 8, 2026, in Neurology^® found that eating a high-quality plant-based diet may be linked to a lower risk of Alzheimer’s disease and other forms of dementia—even when people adopt these eating habits later in life.

The study followed nearly 93,000 adults for an average of 11 years and included African American, Japanese American, Latino, Native Hawaiian, and White participants. They were an average age of 59 at the start. Over the course of the study, more than 21,000 participants developed Alzheimer’s disease or another form of dementia.

Researchers looked at different types of plant-based diets—not just whether people ate plant foods, but the quality of those foods. A healthful plant-based diet includes whole grains, fruits, vegetables, nuts, legumes, and vegetable oils, along with beverages like tea and coffee. An unhealthful plant-based diet has more refined grains, sugary foods and drinks, fruit juice, and potatoes, often eaten in fast foods or processed meals. The study did not focus on vegetarian or vegan diets.

After accounting for factors such as age, physical activity, and diabetes, researchers found that people who followed a healthful plant-based diet more closely had a lower risk of developing dementia. In contrast, those who ate a more unhealthful plant-based diet had a higher risk.

Importantly, the researchers also looked at how diet changes over time. During the course of the study, participants whose diets shifted toward more unhealthful plant-based foods had a higher risk of dementia. Those who moved away from unhealthful plant-based eating had a lower risk.

“Plant-based diets have been shown to be beneficial in reducing the risk of diseases like diabetes and high blood pressure, but less is known about the risk of Alzheimer’s disease and other dementias,” said study author Song Yi Park, PhD, of the University of Hawaii at Manoa. “Our study found that the quality of a plant-based diet mattered.”

The researchers note that the study shows an association, not proof that diet directly prevents dementia. Diet information was self-reported, which may also limit accuracy. Still, the findings suggest that choosing healthier plant foods and limiting heavily processed options may support better brain health as people age.

Key Takeaways

• In this study, healthful plant-based foods were linked to lower dementia risk, while unhealthful plant-based foods were linked to higher risk.
• Participants who improved their diet quality after age 60 were associated with lower dementia risk.
• This study does not prove that a higher quality plant-based diet causes a lower risk of dementia.

This article was medically reviewed by Sarah Song, MD, MPH, FAAN.