Veggies such as spinach, kale, arugula, and Swiss chard are all great sources of folate, or Vitamin B9, which is shown to improve cognition in older adults. Folate helps ward off depression (a common dementia side-affect) by contributing to serotonin levels. Vitamin E in leafy green vegetables has also shown positive effects on the brain. At least two servings a week can help, and researchers found six or more servings a week provide the greatest brain benefits.
In a 2018 study involving adults who were 58 years to 99 years old, eating green leafy vegetables was associated with the equivalent of being 11 years younger cognitively. Other studies published in 2005 found a reduced risk of dementia in those with higher levels of folate which is found in leafy green vegetables.