Factors involved in cancer

The risk of cancer is affected by:

Genetic factors: People who have a family history of a particular cancer are more likely to develop it themselves.

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Environmental factors: A range of environmental factors affect the development of a large proportion of cancers to varying degrees. Examples are tobacco smoke, diet, alcohol, some chemicals, and many other aspects of lifestyle, e.g., physical activity and body weight.

Hormonal Factors: The risk of some cancers, e.g., some breast cancers, is linked to levels of certain hormones in the body.

Environmental factors and cancer

A large proportion of cancers are influenced by environmental factors. Research has been done to compare the most common types of cancers in different groups of people. This has shown that:

  • Some forms of cancer are more common in countries that have particular habits, e.g., stomach cancer is more common in parts of China where there is a high consumption of salted foods.
  • People who move from one country to another have a greater risk of the cancers more commonly seen in the country they move to (after a period of time); this is probably due to changes in diet and lifestyle.
  • Groups of people who have a very different lifestyle from others in a community tend to have different patterns of cancer, e.g., religious groups.

These types of studies do not show that a particular factor causes cancer, but they suggest links between aspects of lifestyle and cancer. These links are often examined in more detail by studying people with cancer.

Diet and cancer

Diet has a greater influence on some types of cancer than others. The strongest links are with some cancers of the gastrointestinal tract, including those of the mouth, throat, stomach, and large bowel (colon), and some hormone-related cancers, such as breast cancer.

Approximately 30% of cancers could be prevented by dietary means in Western countries. It is estimated that a one-fifth to one-third of the incidence of some of the most common cancers could be prevented by maintaining a healthy body weight and being physically active.