To further explore this association and to evaluate individual nutrients in green leafy vegetables, researchers conducted another prospective study, which was published in 2018 in the journal Neurology.
The study sample consisted of 960 participants of the Rush Memory Aging Project, an ongoing prospective cohort study of older adults in the Chicago area.
Participants were an average age of 81 years, 95% white and 74% female.
They completed a baseline food frequency questionnaire, which asked about the following green leafy vegetables: cooked spinach (½ cup), cooked kale/collards/greens (½ cup), and raw lettuce salad (1 cup).
Participants were followed for up to 10 years (mean follow up = 4.7 years) and evaluated annually with a battery of 19 cognitive tests, which assessed five cognitive domains.
Cognitive scores for the overall sample declined steadily with time.
After adjusting for education, participation in cognitive and physical activities, smoking, alcohol consumption and seafood consumption, consumption of green leafy vegetables was positively and significantly associated with a slower rate of cognitive decline.
The rate of cognitive decline in participants who consumed a median of 1.3 servings of green leafy vegetables per day was slower than those who rarely or never consumed green leafy vegetables, by an effect size that was equivalent to being about 11 years younger.
Analysis of individual nutrients in green leafy vegetables indicated that higher intake of folate, phylloquinone and lutein were each linearly associated with slower cognitive decline.
These nutrients may exert independent mechanisms of action and also work synergistically within green leafy vegetables to confer protective cognitive effects.
The conclusion of this study is simple: eating at least one serving of green leafy vegetables per day may be a simple way for aging adults to slow cognitive decline.
