Dementia and cognitive decline are becoming more of a public health issue as our population ages. Recent data show adults continue to consume too few fruits and vegetables; overall, 12.2% met fruit intake recommendations and 9.3% met vegetable intake recommendations during 2015. Consumption was lower among men, young adults, and adults with greater poverty. I may add that most of the favored choices of vegetables in the U.S. are potatoes (starchy) followed by tomatoes (not exactly green or leafy). Scientifically speaking the tomato is a fruit. However, FYI, Nix v. Hedden, 149 U.S. 304 (1893), was a decision by the Supreme Court of the United States that, under U.S. customs regulations, the tomato should be classified as a vegetable rather than a fruit.
A recent study published in Neurology reported that consuming more non-starchy leafy greens and cruciferous (broccoli and cauliflower) vegetables had a preventive effect on mental decline in an older population (average age was 81). However, any increase in any vegetable intake appears to be one of the smartest thing you can do for your heart and/or brain. It also helps to tailor your diet to a more plant-based approach.