Stop a common culprit with yogurt. Ice cream, popsicles, sodas– indulging in sweet, sugary summer treats can lead to an over-growth of yeast in the digestive tract, which produces waste products that can dampen alertness and energy levels, explains Elson Haas, MD, director of the Preventative Medical Center of Marin in California. Give yogurt a try. Sugar-free yogurt is made with live bacterial cultures. Studes suggest this is enough to wipe out trouble-makers in 67% of women. Add your favorite summer berries!