Carcinogen

A carcinogen is a substance that causes a normal cell to change into a cancerous cell. The word "car cinogen" is derived from Greek and means in English, cancer-causing. Carcinogens fall into two broad categories, naturally occurring substances that are found in food or soil, or artificial substances created by chemists for various industrial purposes. Although the way carcinogens cause cancer is still not completely understood, cancer researchers believe that humans and other animals must be exposed to a carcinogen for a certain period of time and at a high enough concentration for cancer to occur.

Cancer is a group of diseases in which cells grow abnormally. Like all living things, normal cells grow, reproduce, and die. These processes are controlled by chemicals and reactions within the cell, which are in turn controlled by the cell's genetic material within its nucleus. In a cancerous cell, the genetic material is altered, and the genes which encode and direct the chemical reactions within the cell are mutated, or changed. Cancerous cells grow uncontrollably, forming a large mass of cells called a tumor, which invades tissues and kills non-cancerous cells. Sometimes cancerous cells "break off" from a tumor and enter the bloodstream, traveling to other parts of the body and infecting other organs and tissues in a process known as metastasis. In this way, a cancer can spread from an isolated tumor to the entire body.

Several agents, such as viruses, medication, and synthetic carcinogens can cause mutations within a cell's genetic material. Some kinds of cancers are caused by viruses. For example, a special kind of virus called a retrovirus causes a rare form of leukemia (cancer of the white blood cells). Radiation from naturally-occurring radioactive substances (such as uranium) can disrupt a cell's genetic material and bring about cancer. Synthetic carcinogens are found in processed foods and industrial chemicals.

It is recommended that people eat a varied diet high in fresh fruits and vegetable and avoid excess consumption of foods high in nitrites. While it is not possible to completely eliminate one's exposure to carcinogens, it is possible to avoid the concomitant risk factors that may lead to cancer. Avoiding smoking, eating a varied, balanced diet that includes fiber, and limiting alcohol consumption are all associated with a lowered cancer risk.