A new study from the British Medical Journal showed that cognitive decline-a decrease in memory and reasoning capacity-can start to affect our brains as early as 45! Give yourself a mental boost now with these four foods. 

Leafy Greens 

A study in Neurology showed that people who ate two or more daily servings of vegetables, especially leafy greens, had the mental focus of people five years their junior. Have a big salad for lunch; serve some sautéed spinach at dinner. 

Whole Grains 
Studies show that eating a breakfast of whole grains helps sustain mental focus better than a morning meal of refined carbohydrates or no breakfast at all. Two to try: whole-grain cereal with milk or eggs with whole-wheat toast. 

Coffee 
It might come as no surprise that coffee can help your mind feel sharper (goodbye, morning brain fog!), but did you know that coffee affects men and women differently? Men actually feel more alert more quickly than women do after drinking a caffeinated beverage, according to research from the University of Barcelona. In the study, men reported feeling less drowsy after only 10 minutes and sustained the mental boost for a half hour. Women got a "kick" from the espresso, too, but rated it weaker than the men did. But women, it turns out, are more influenced by the placebo effect when it comes to caffeine. Just anticipating the stimulating effects of caffeine may be enough to feel them. When the same researchers had participants drink decaf, women reported feeling significantly more alert than men, who reported just a slight boost. 

Gum 
It's not technically a food, but a recent study found that people who chewed gum during a stressful task were more alert afterwards than when they did the task without gum.