Summer’s unrelenting heat and humidity are physiological stressors, and they can dampen your brain’s ability to produce mood-elevating beta waves. But inhaling the sweet, tangy aroma of lemon, orange or any other citrus can kick-start beta wave production, raising your alertness and energy levels by 50 percent or more within two minutes, says Alan Hirsch, M.D., medical director of Chicago’s Smell and Taste Treatment and Research Foundation. Try it: Open a bottle of citrus essential oils (available in health food stores) and inhale deeply. Or enjoy a half cup serving of the fresh fruit! “Be sure to savor the citrusy smell while you eat, so the odor molecules can actually reach, and stimulate, your brain,” says Dr. Hirsch.