Flavonoids, vitamin e, and vitamin c all help the lungs function at their best. apples are rich in all of these and those who eat several a week have healthier lungs. apples are rich in antioxidants which can help keep your lungs healthy. 9. grapefruit. naringin, a flavonoid in grapefruit, inhibits the activation of a cancer-causing enzyme. In healthy people without chronic lung disease, even at maximum exercise intensity, we only use 70 percent of the possible lung capacity. ” why is lung capacity important? lung capacity predicts health and longevity. a 29-year study published in chest concluded that lung capacity is a long-term predictor of respiratory mortality, and should be. Home Lung Function Test How To Test Your Lung Function How to increase lung capacity: simple exercises. Vital capacity is the maximum amount of air the volunteers could exhale from their lungs. the researchers concluded that deep breathing, even for just a few minutes, was beneficial healthy capacity lu...