Unit 7
Diet and Cancer

Overview

Investigating the cause and effect relationship between diet and cancer is a complex undertaking. A major reason for the complexity is that the various dietary factors are highly interrelated. For instance, populations that consume a low-fat/high-fibre diet have a low incidence of the Western cancers. But is this a cause and effect relationship? It might be; but on the other hand, it could be that this dietary pattern is associated with some other factor, the true protective factor. Possible protective factors might be exercise, a diet rich in plant foods, not smoking, or a thousand and one other things. In this unit, we explore the fascinating, but confusing, relationship between diet and cancer.

Based on a variety of evidence, there is a consensus that about thirty-five to forty per cent of cancer deaths can be attributed to diet. A great number of chemicals are thought to pose a risk of cancer, and many of these substances can enter our bodies through our food. However, this unit will focus on what are probably the most important aspects of our diet. Areas not covered here include food additives, pesticides, smoked meat and fish, and industrial pollutants in the food chain.

Objectives

After completing this unit, you should be able to

1. discuss the possible role of fat in cancer of the colon and breast, and of dietary fibre in cancer of the colon.
2. describe the possible protective action of beta-carotene, selenium, and vitamins C and E against various types of cancer.
3. describe the general protective action of fruit and vegetables against cancer.
4. discuss the possible role of excess energy intake as a cause of cancer.
5. discuss the association of salt with stomach cancer.
6. discuss the different research techniques used to elucidate the role of diet in cancer.