One of the biggest predictors of mental decline as we age is obesity, unfortunately. A new study suggests (not the best study) that green tea extract improves attention and memory in elderly with mild cognitive impairment.
I drink green tea (unsweetened) every day. It appears to suppress appetite and facilitate weight loss. When I was starting on my weight loss, and got hungry in between meals, I would first drink a cup of green tea and try to wait 30 min before eating. Many times, 30 min later, I was no longer hungry!