Eating a high-quality plant-based diet is associated with a lower risk of Alzheimer’s disease and other related dementias compared to eating a lower-quality plant-based diet, according to a study published in the journal Science on April 8, 2026. Neurology®Medical Journal of the American Academy of Neurology. Although this study shows an observational association, it does not prove that a high-quality plant-based diet reduces the risk of dementia.
Researchers investigated three plant-based diets. A holistic plant-based diet prioritizes plant foods over animal products such as meat, milk, and eggs, regardless of quality. A healthy plant-based diet prioritizes healthy plant foods such as whole grains, fruits, vegetables, vegetable oils, nuts, legumes, and tea and coffee. An unhealthy plant-based diet includes less-healthy plant foods such as refined grains, fruit juices, potatoes, and added sugars. The researchers did not look at vegetarian or vegan diets.
“Plant-based diets have been shown to be beneficial in reducing the risk of diseases such as diabetes and high blood pressure, but less is known about the risk of Alzheimer’s disease and other dementias,” said study author Son-Yi Park, Ph.D., of the University of Hawaii at Manoa Cancer Center in Honolulu. “Our study found that the quality of plant-based diets is important, with high-quality diets associated with reduced risk and poor-quality diets associated with increased risk.”
The study involved 92,849 participants with an average age of 59 years at the start of the study. African American, Japanese American, Latino, Native Hawaiian, and Caucasian participants were included. They were followed for an average of 11 years. During that time, 21,478 people developed Alzheimer’s disease or other related dementias.
Participants completed a dietary questionnaire at the beginning of the study. Researchers determined how similar people’s diets were to an overall plant-based diet, a healthy plant-based diet, and an unhealthy plant-based diet by considering how much animal fat, meat, dairy, eggs, fish, and seafood they ate, as well as healthy and unhealthy plant foods. Participants were each given three scores based on how closely they followed three plant-based diets.
The researchers then ranked the participants into five subgroups on each of the three dietary scores.
After adjusting for factors such as age, physical activity and diabetes, researchers found that when people were compared based on their overall plant-based diet score, the top subgroups who consumed the most plant foods had a 12% lower risk of dementia compared to the lowest subgroups. When people were compared based on their healthy plant-based diet scores, the highest subgroup had a 7% lower risk compared to the lowest subgroup. And when compared based on unhealthy plant-based diet scores, the top subgroups who ate the least healthy plant foods had a 6% higher risk of dementia than the lowest subgroups.
Of the small group of 45,065 participants who reported eating again 10 years later, 8,360 participants later developed dementia. Researchers observed changes in diet over time. Compared to people whose diet remained unchanged, those who made the most dietary changes toward unhealthy eating habits had a 25% higher risk of dementia, and those who made the most dietary changes away from unhealthy eating habits had an 11% lower risk.
“We found that adopting a plant-based diet and avoiding low-quality plant-based diets even at later ages is associated with a lower risk of Alzheimer’s disease and other dementias,” Park said. “Our findings highlight the importance of not only following a plant-based diet, but also ensuring that the diet is of high quality.”
A limitation of the study was that the researchers assessed diets based on dietary questionnaires completed by participants, who may not remember all the details of their meals accurately.
This research was supported by the National Institutes of Health’s National Institute on Aging and the National Cancer Institute.
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American Academy of Neurology
