What Causes Cancer?

Cancer is not one disease, but more than 200 that develop similarly. At the genetic level, something goes wrong with cell reproduction. Instead of dividing normally, cells that become cancerous reproduce wildly, producing abnormal growths (tumors). Tumor cells spread (metastasize) around the body, growing additional tumors. If tumor growth can’t be stopped, it interferes with vital body processes, and eventually, the person dies.

What Causes Cancer?

• Genetics. All cancers affect our genes. But some families have genes that are pre-programmed to turn cells cancerous. Some cancers have strong genetic components, for example, breast, ovarian, and colorectal. In high-risk families, many members develop the disease, and get diagnosed unusually early in life. But any family history of cancer raises your risk somewhat.

• Smoking. About one-third of cancers are caused by smoking, according to the ACS. Smoking vastly increases the number of highly reactive oxygen ions (free radicals) in the bloodstream. Free radicals cause cell damage including damage to DNA, the complex molecule in the chromosomes of cell nuclei that stores genetic information. The body’s immune system can usually repair free-radical damage, but after decades of smoking, the steady onslaught of free radicals overwhelms the body’s repair mechanisms, and DNA damage may express itself as cancer.

• High-fat, low-fiber diet. Approximately one-third of cancers are caused by a high-fat, low-fiber diet, says Marion Nestle, Ph.D., professor and chair of the Department of Nutrition and Food Studies at New York University. A high-fat diet, particularly one high in animal fat, introduces free radicals into the bloodstream. A low-fiber diet means few plant foods. Plant foods are the source of antioxidant nutrients, among them, vitamins A, C, and E, and the mineral, selenium that help prevent free-radical damage and promote cell repair. “After smoking, diet is the single biggest cancer risk factor we can control,” Dr. Nestle explains. “The research is overwhelming that cancer risk can be reduced substantially through good diet.” Good diet also helps treat cancer.

• Exposure to environmental carcinogens. Exposure—usually but not always prolonged exposure—to many industrial chemicals, toxic wastes, drugs, and pesticides can increase cancer risk. Radiation from nucelar weapons and nuclear power plants can also cause cancer.