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Energy Booster
In a 2013 study, subjects reported a 38 percent decline in fatigue and a 31 percent increase in energy after eating two gold kiwis a day for six weeks. A single serving provides more than 100 percent of your recommended dietary allowance (RDA) for vitamin C, which may account for the fruit's rejuvenating properties; the vitamin is required in order to activate key enzymes involved in energy production and brain function.

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Focus Finder
Plenty of foods can help boost cognition in the long term, but blueberries may keep your brain working well right now. Researchers from the University of Reading found that people performed better on memory and concentration tests five hours after drinking a smoothie made with about one and a half cups of blueberries than they did after downing a blueberry-free concoction. Scientists believe that the berry's flavonoid compounds improve alertness by increasing oxygen flow to the brain.

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Stress Buster
Nibbling on a handful of walnuts may help you keep your cool during anxiety-inducing situations, according to a study in the Journal of the American College of Nutrition. After consuming a daily dose of walnuts (and walnut oil) for six weeks, participants' blood pressure was 2 to 3 points lower when they were asked to give a speech compared with the BP of subjects who hadn't eaten the nuts. Walnuts are rich in fiber, antioxidants and omega-3 fatty acids—all nutrients that may help temper your vascular reaction to stress.

Illustrations: LuLu

Happiness Helper
Consuming edamame might aid in beating the blues, thanks to the B vitamin folate. (One cup delivers more than 100 percent of your RDA.) In one study, women with the highest folate levels were 63 percent less likely to report significant symptoms of depression than those with the lowest. Falling short on folate may interfere with the production of feel-good chemicals like serotonin.