Researchers found that people who followed healthier plant-based diets had a lower risk of Alzheimer’s disease and related dementias.
Diet quality appeared to matter, with unhealthy plant-based foods linked to a higher dementia risk.
The findings suggest that even people who adopt healthier eating habits later in life may still benefit.
A growing body of research has explored how food choices affect long-term health, and now scientists are taking a closer look at how diet may influence brain health as people age.
A new study published in Neurology, the medical journal of the American Academy of Neurology, found that people who followed healthier plant-based diets were less likely to develop Alzheimer’s disease and other forms of dementia compared to those whose diets relied more heavily on less nutritious plant-based foods.
Researchers emphasized that the study only found an association and does not prove that diet directly prevents dementia. Still, the findings add to growing evidence that the quality of foods people eat may play an important role in healthy aging.
“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,” researcher study author Song-Yi Park, Ph.D. said in a news release.
“Our study found that the quality of a plant-based diet mattered, with a higher quality diet associated with a reduced risk, and a lower quality diet associated with an increased risk.”
The study
The study focused on several types of plant-based eating patterns. One measured overall plant-based eating, meaning participants ate more plant foods than animal products. Another focused specifically on healthier plant foods such as whole grains, fruits, vegetables, nuts, legumes, vegetable oils, tea and coffee. A third measured less healthy plant-based foods, including refined grains, fruit juice, added sugars and potatoes commonly eaten in processed or fast-food meals.
Importantly, the researchers were not studying vegetarian or vegan diets specifically. Instead, they looked at how much healthy and unhealthy plant-based food people consumed overall.
To conduct the study, researchers followed 92,849 adults with an average starting age of 59. Participants came from a variety of racial and ethnic backgrounds, including African American, Japanese American, Latino, Native Hawaiian and white adults. Over an average follow-up period of 11 years, 21,478 participants developed Alzheimer’s disease or another related dementia.
At the beginning of the study, participants completed detailed food questionnaires about their eating habits. Researchers then scored each participant based on how closely their diets matched the three plant-based eating patterns. Factors such as meat, dairy, eggs, seafood, healthy plant foods and less healthy plant foods were all included in the scoring process.
The research team also examined how people’s diets changed over time. A smaller group of more than 45,000 participants completed a second dietary questionnaire about 10 years later, allowing researchers to compare how shifts in eating habits related to dementia risk.
The results
After accounting for factors like age, exercise levels and diabetes, researchers found noticeable differences between dietary patterns.
People who consumed the highest amounts of plant foods overall had a 12% lower risk of dementia compared to those who consumed the least. Those who most closely followed a healthier plant-based diet had a 7% lower risk.
Meanwhile, participants whose diets contained the highest amounts of unhealthy plant-based foods had a 6% higher risk of dementia.
Researchers also found that dietary changes over time appeared to matter. People whose diets became more unhealthy over the 10-year period had a 25% higher risk of dementia, while those who moved away from unhealthy eating patterns had an 11% lower risk.
“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 study authors say the findings suggest that adopting healthier eating habits — even later in life — may still be associated with better brain health outcomes. However, they also noted an important limitation: the study relied on self-reported food questionnaires, meaning participants may not have remembered their diets perfectly.