Eating a high-quality plant-based diet might lower your risk of Alzheimer's disease and other dementias. However, eating an unhealthy plant-based diet could raise this risk. This is according to a new study published in Neurology, the medical journal of the American Academy of Neurology.
The study found a connection, but it doesn't prove that a healthy plant-based diet directly prevents dementia.
The Quality of Plant-Based Diets Matters
Researchers looked at three types of plant-based diets. An "overall plant-based diet" meant eating more plant foods than animal products like meat, milk, and eggs. This didn't consider how healthy the plant foods were.
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Start Your News DetoxA "healthful plant-based diet" focused on foods like whole grains, fruits, vegetables, vegetable oils, nuts, legumes, tea, and coffee. An "unhealthful plant-based diet" included foods such as refined grains, fruit juices, potatoes, and added sugars. The study did not specifically look at vegetarian or vegan diets.
Song-Yi Park, PhD, a study author from the University of Hawaii at Manoa’s Cancer Center, explained that plant-based diets are known to help reduce risks for diseases like diabetes and high blood pressure. However, less is known about their effect on Alzheimer's. Park noted that their study showed the quality of the plant-based diet was important. A higher quality diet was linked to a lower risk, while a lower quality diet was linked to a higher risk.
Tracking Diet and Dementia Risk
The study followed 92,849 adults, with an average age of 59 at the start. Participants came from various ethnic backgrounds, including African American, Japanese American, Latino, Native Hawaiian, and white adults. Over about 11 years, 21,478 participants developed Alzheimer’s disease or another type of dementia.
At the start, participants filled out food questionnaires. Researchers then scored how closely each person's diet matched the three plant-based diet patterns. These scores included healthy and less healthy plant foods, as well as animal fats, meat, dairy, eggs, fish, and seafood.
After considering factors like age, physical activity, and diabetes, researchers found interesting results. Participants who scored highest for the overall plant-based diet had a 12% lower risk of dementia. Those with the highest scores for the healthful plant-based diet had a 7% lower risk. In contrast, people who ate the most unhealthy plant-based foods had a 6% higher risk of dementia.
Long-Term Diet Changes and Brain Health
The study also looked at a smaller group of 45,065 participants who reported their diets again after 10 years. Among them, 8,360 later developed dementia.
The findings showed that people whose diets shifted more towards unhealthy plant-based foods had a 25% higher risk of dementia. This was compared to those whose diets stayed about the same. On the other hand, participants who moved away from unhealthy plant-based eating had an 11% lower risk.
Park emphasized that adopting a plant-based diet, even later in life, and avoiding low-quality plant-based diets were linked to a lower risk of dementia. The study highlights that it's crucial not just to follow a plant-based diet, but to make sure it's a high-quality one.
One limitation of the study is that diet information came from self-reported questionnaires. These might not always perfectly reflect what people actually ate.
Deep Dive & References
Plant-Based Dietary Patterns and Risk of Alzheimer Disease and Related Dementias in the Multiethnic Cohort Study - Neurology, 2026
