What causes cancer?
It is rarely possible to find the cause of a cancer in an individual, but studies on groups of people with cancer have shown specific risk factors to be associated with specific cancers. This suggests that different types of cancer probably have different causes. These studies also indicate that cancer formation is a multi-step process, and that for most cancers the time from a cancer-causing exposure to a clinically diagnosable cancer averages about 20 years. Among the known risk factors for cancer, tobacco stands out. Cigarette smoking is associated with lung cancers, and with a substantial proportion of cancers of the bladder, mouth and throat, stomach, pancreas and others. Diet is also a risk factor; higher cancer rates are seen in people who eat a diet high in fat and low in fresh vegetables and fruits. It is estimated that diet and tobacco together account for approximately two out of three cancers.
We are not sure what specifically causes cancer. However, we do know that several factors can contribute to cancer development. These factors may be external such as exposure to chemical substances, or internal such as a genetic predisposition to developing cancer. Anyone is at risk for developing cancer, however most cases occur in adults who are middle-aged or older, those who have a family history of cancer, or those who participate in potentially cancer causing behaviors like using tobacco products or getting too much sun.
There is no single causal relationship for cancer. In experimental animals many agents, including chemicals, hormones, viruses and radiation, have produced cancer. There is a casual relationship between tobacco consumption and head and neck cancers. According to the W.H.O., 90% of the people who suffer from head and neck cancers have used tobacco in some form or the other.
There are many causes of cancer, and for some cancers there may be no known cause. Activities such as tobacco smoking and excessive alcohol consumption can increase the risk of developing cancers. Tobacco use is linked with increased risk of cancers of the mouth, throat, lungs, bladder, kidneys as well as other sites. Not everyone who smokes will develop a cancer, and not everyone who does not smoke or drink alcohol will be spared from developing a cancer. Exposure to radiation (x-rays) can cause cancer. The x-rays used by your physician or dentist are relatively low in energy, and are well regulated when used, so that these procedures are very safe. Too much exposure to sunlight without any protection can cause skin cancer. There are many dietary issues that have been show to have an effect on increasing the risk of developing some forms of cancer, such as excessive eating of animal fat with an increased risk of colon cancer.
We do not know all of the risks and causes of cancer. However, there are a number of chemical, physical and biological agents that have been shown to trigger the mistakes in the cell blueprint that cause cancer. These are called carcinogens and include tobacco, ultraviolet radiation and asbestos. A number of cancers share risk factors: • one in nine cancers, and one in five cancer deaths, are due to smoking • about 3% of cancers are related to alcohol consumption • many cancers occur as a direct result of dietary influences, from infectious agents or exposure to radiation (especially skin cancers from ultraviolet radiation) • some cancers result from inherited ‘faulty’ genes • cancer is NOT caused by injury or stress.
