April 22, 2026
Experts encourage a plant-based diet for better overall health, including the health of the brain. But not all plant-based diets are equally healthy, according to a new report. The study found that some plant foods are better for the brain than others, and that it’s never too late to start eating in ways that may help to lower your risk of developing Alzheimer’s disease.
“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 of the University of Hawaii at Manoa’s Cancer Center in Honolulu. “Our study found that the quality of a plant-based diet mattered. A higher quality diet was associated with a reduced risk, and a lower quality diet associated with an increased risk.”
For the study, published in Neurology, Dr. Park and his colleagues began by looking at 92,849 men and women whose average age was 59. They included a diverse mix of ethnicities: African American, white, Japanese American, Latino, and Native Hawaiian.
At the start of the study period, participants completed detailed questionnaires about their typical diets, including how closely they adhered to a general plant-based diet. Such a diet prioritizes fruits, vegetables, olive oil and other plant-based foods over animal-based products like meat or butter. The researchers did not consider whether someone followed a strict vegetarian or vegan diet, but rather how their general eating patterns incorporated plant foods into their daily routines.
The researchers then considered the quality of their plant-based diets. High-quality plant-based foods are generally considered to be better for overall health and include foods like whole grains, fruits, vegetables, vegetable oils, nuts, legumes and tea and coffee. The unhealthful plant-based diet includes less healthy plant foods like refined grains, added sugars, fruit juices and potatoes that tend to be eaten as part of fast foods or processed food products.
Researchers followed the participants for an average of 11 years. During that time, 21,478 people developed Alzheimer’s disease or another form of dementia.
After adjusting for factors like age, physical activity and diabetes, researchers found that those who ate the most plant foods overall had a 12 percent lower risk of dementia compared to those who ate the least. Eating more healthful plant-based foods was associated with lower dementia risk, while eating less healthful plant foods was associated with an increased risk. The study showed only an association and cannot prove cause and effects, but the findings bolster growing evidence that a plant-based diet promotes brain health.
The researchers also looked a smaller subset of 45,065 participants who had completed a second dietary questionnaire 10 years after the first. Among that group, 8,360 later developed dementia.
The researchers found that compared to those whose diet didn’t change over that period, those who cut many of the unhealthy plant-based foods from their diet had a 11 percent lower risk of Alzheimer’s or other forms of dementia. The older adults who increasingly ate more unhealthy plant-based options, such as refined grains and foods with added sugars, on the other hand, were about 25 percent more likely to develop some type of dementia.
“We found that adopting a plant-based diet, even starting at an older age, and refraining from low-quality plant-based diets were associated with a lower risk of Alzheimer’s and other dementias,” said Dr. Park. “Our findings highlight that it is important not only to follow a plant-based diet, but also to ensure that the diet is of high quality.”
The findings also underscore it’s never too late to start. Choose whole grains over refined ones. Think more fruits, vegetables, nuts and seeds and less red meat and eggs. Opt for an apple or orange over fruit juice, and olive oil over butter. Even small changes now, no matter your age, may lead to sizable brain benefits years down the road.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Song-Yi Park; Veronica Wendy Setiawan; Eileen M. Crimmins; et al: “Plant-Based Dietary Patterns and Risk of Alzheimer Disease and Related Dementias in the Multiethnic Cohort Study.” Neurology, April 8, 2026
