Take a tablespoon of lemon juice at least one hour before each meal to relieve asthma. Vitamin C is an antioxidant nutrient. It supports immune system function and helps protect your cells from damage caused by free radicals. According to the National Cancer Institute, free radicals are charged atoms or groups of atoms with an odd number of electrons, which can be formed when oxygen interacts with certain molecules. Once formed, they can react with important components within cells, such as DNA and cell membranes, impairing their function.