Unit 13
Diet and Cancer

Cancer is a broad disease family covering over 170 types of cancer. Lifestyle factors contribute to many of them. This unit will focus on nutrition links to the leading types of cancer: lung, colon, rectal, and breast cancers. About 30% of all Canadian deaths are caused by cancer. Two-thirds of these cancers (20% of deaths) are caused by the top four cancers: lung (and respiratory organs), 26.4%; colon, rectum, and other digestive organs, 25.5%; breast cancer 7.7%; and prostate cancer, 5.7%. There is a perception that breast cancer is a leading cause of death for women, yet almost four times as many women die from heart disease as from breast cancer (see Study Guide, Table 11.1, Unit 11). Still, there are diet and lifestyle choices that will lower women’s risks for both breast cancer and heart disease.

Investigating the cause-and-effect relationship between diet and cancer is a complex undertaking, largely because the various dietary factors are highly interrelated. For example, populations that consume a low-fat/high-fibre diet have a low incidence of cancers that are common in the Western world. But is this a cause-and-effect relationship? It might be. On the other hand, this dietary pattern could simply be associated with the true protective factor. Possible protective factors might be exercise, a diet rich in plant foods, not smoking, or many other things.

Objectives

After completing this unit, you should be able to

1. identify the role of diet and obesity in causing cancer.
2. discuss how interpreting the results of research studies on the relationship between diet and risk of cancer is problematic.
3. discuss the role of fruit, vegetables, and whole grains in cancer prevention.
4. discuss dietary factors that help prevent colon cancer, and describe the known mechanisms by which this occurs.
5. discuss the relationship between diet, lifestyle, and breast cancer.
6. discuss the role of selenium and vitamin D in cancer.
7. describe the role of salt in the development of stomach cancer.