A high-quality plant-based diet may lower the risk of dementia, while lower-quality plant foods might increase it, according to new research. Not all plant-based diets have the same impact on brain health.
The main question in preventive care is not just whether people follow plant-based diets, but specifically what those diets include.
“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’s Cancer Center. “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.”
Study Tracks Diet and Dementia Risk
Researchers followed 92,849 adults with an average age of 59 for approximately 11 years. The group included participants from multiple racial and ethnic backgrounds. During that time, 21,478 participants developed Alzheimer’s disease or another related dementia.
Participants completed food questionnaires at the start of the study. Researchers evaluated how closely diets aligned with three patterns: an overall plant-based diet, a healthful plant-based diet, and an unhealthful plant-based diet.
A healthful plant-based diet emphasized whole grains, fruits, vegetables, vegetable oils, nuts, legumes, tea, and coffee. An unhealthy version included refined grains, added sugars, fruit juices, and potatoes commonly consumed in processed or fast foods.
Healthier Choices Linked to Lower Risk
After adjusting for factors such as age, physical activity, and diabetes, differences across dietary patterns became clear.
Participants with the highest intake of plant-based foods overall had a 12 percent lower risk of dementia compared to those with the lowest intake. Those who most closely followed a healthful plant-based diet had a 7 percent lower risk. In contrast, those with the highest intake of unhealthful plant-based foods had a 6 percent higher risk.
Diet Changes Over Time Also Matter
A subgroup of 45,065 participants completed a second dietary assessment 10 years later, allowing researchers to examine how changes in eating habits affected outcomes.
Among this group, 8,360 participants developed dementia. Compared with individuals whose diets remained stable, those whose diets shifted most toward unhealthful plant-based foods had a 25% higher risk. Those who moved away from unhealthful patterns had an 11 percent 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,” Park said. “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.”
What the Findings Mean for Practice
The study suggests diet quality is important for long-term brain health.
The main takeaway for nurses and healthcare teams is that advising patients to focus on whole, minimally processed plant foods is more effective for brain health than simply recommending a general increase in plant-based intake. Prioritizing diet quality is key.
Limitations
Researchers noted that dietary data were based on self-reported questionnaires, which may not capture every detail accurately.
