Title: Risk Factors for Cancer - Cancer - Merck Manuals Consumer Version
Headings: Risk Factors for Cancer
Risk Factors for Cancer
Family history
Genes and chromosomes
Age
Environmental factors
Geography
Diet
Drugs and medical treatments
Table
Some Carcinogens
Infections
Inflammatory disorders
Drugs Mentioned In This Article
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Content: Many other substances have been investigated as possible causes of cancer, but more study is needed to identify those chemicals that increase the risk of cancer. Geography
The risk of cancer varies according to where people live, although the reasons for the geographic differences are often complex and poorly understood. This geographic variation in cancer risk is probably multifactorial: a combination of genetics, diet, and environment. For example, the risk of colon cancer and breast cancer is low in Japan, yet in Japanese people who immigrate to the United States, the risk increases and eventually equals that of the rest of the American population. In contrast, the Japanese have extremely high rates of stomach cancer. When these people immigrate to the United States and eat a Western diet, the risk declines to that of the United States, although the decline may not be evident until the next generation. Diet
Substances consumed in the diet can increase the risk of cancer. For instance, a diet high in unsaturated fat, and obesity by itself, have been linked to an increased risk of colon, breast, and possibly prostate cancer. People who drink large amounts of alcohol are at much higher risk of developing head and neck cancer and esophageal cancer.