People who ate one serving of green, leafy vegetables performed better on learning/memory tests and showed an equivalent of being 11 years younger cognitively than people who rarely ate them. This was an observational study so causation cannot be established. However, this study accounted for other factors that may affect brain health including seafood and alcohol consumption, smoking, high blood pressure, obesity, education level and amount of physical and cognitive activities. Additionally, randomized controlled trials with certain compounds such as lutein, which is enriched in dark leafy greens, have shown that cognition is improved after supplementing with lutein.