The findings indicate that prioritising whole grains, fruits, vegetables and other nutritious plant-based foods in midlife — and even when adopted at older ages — may help protect cognitive function as people age.

The study, published on 8 April, 2026, found that adults who emphasised healthy plant foods over refined carbohydrates, added sugars and highly processed items had lower rates of dementia in later life. Those who improved the quality of their diet over a decade also showed reduced risk, while people whose diets became poorer had increased risk.

Researchers defined a healthful plant-based diet as one rich in whole fruits and vegetables, whole grains, legumes, nuts, vegetable oils, tea and coffee. In contrast, less healthy plant-based diets included large amounts of refined grains, sugary products and certain processed foods. In the cohort analysed, individuals with higher intake of healthy plant foods had notably lower dementia risk compared with those eating mostly less-healthy plant options.

Although the research highlights an association rather than a direct cause-and-effect relationship, experts say it reinforces broader evidence that diet quality matters for brain health. Even those who begin dietary changes later in life may gain cognitive benefits, the study suggests.

The results add to a growing body of evidence emphasising plant-forward eating as part of lifelong health, with other studies linking such dietary patterns to lower risks of cardiovascular disease and overall mortality.