Humans constantly produce cancer cells, which are quickly destroyed by healthy immune systems. Although many people do not realize it, cancer is a normal part of a healthy body. This normal process can get out of control, and cancer cells grow into dangerous tumors. If an immune system does not destroy these cells, it can spell doom for the victim Cancers are responsible for 25 percent of all deaths in the United States. Of these, three of every ten cases is from lung cancer. Billions of dollars are spent every year treating the diseases, making it one of the largest of all branches of medical care. Some critics charge the healthcare industry has the wrong idea about care. Many caretakers are looking at strengthening immune systems to reduce the rates of large cancers. This healthcare mindset is centered on prevention, encouraging the body to treat itself naturally.