Vitamin C is an antioxidant that aids in the formation of collagen and serotonin. It may help strengthen your immune system, boost energy levels, and even reduce Asthma symptoms as it plays a role in a variety of functions within the body. Our bodies cannot make vitamin C, so dietary and/or supplemental intake is necessary. Foods high in vitamin C include: citrus foods, bell peppers, strawberries, and kiwis.  While vitamin C has essential functions and vitamin C containing foods are delicious, be cautious of vitamin C overload as too much may cause diarrhea, kidney stones, or an increase in iron stores. When looking for a supplement look for 250 mg at one time as that is what is absorbed. Anything higher and it may be excreted.