Basically, the stronger your immune system the healthier you are and, as a consequence, the more protected you are from environmental factors that lead to infection and sickness. If you eat foods that are rich in the nutrients your body needs it is able to keep you strong at a cellular level. You are giving the body the tools it needs to keep your immune system strong. A strong immune system supports individuals having fewer colds and viruses and they are better equipped to fight off illnesses at all levels, be that colds or chronic diseases.