A recent survey of over 2000 teens found that those who had a low intake of vitamin C found in fruit and a low intake of vitamin E found in vegetables and nuts were more likely to have asthma. In addition, those who ate foods with a lower intake of omega-3 fatty acids that is found in fish, walnuts and flax seed also had more lung problems. It appears that the antioxidant property of vitamins C and E and the anti-inflammatory effect of the fish oil help to protect the lungs. It is important that your teen has a good, balanced diet rich in fruits, vegetables and foods that contain omega 3 fatty acids.