Many people have a fear of cancer, perhaps because to them it is always an incurable disease. The facts do not support this idea. Countless numbers of Americans who are alive today have had cancer and are now considered to be cured. (“Cured” is defined here as being free of any evidence of the disease for 5 years or more.)

They may have the same life expectancy as others of the same age and sex who have never had cancer, and they can anticipate leading meaningful and productive lives. Despite such impressive statistics, cancer remains a serious disease.

Annually, cancer is diagnosed in more than a million people (excluding non-melanoma skin cancer) and is one of the most significant causes of mortality in the United States. There are more than 100 different types of cancer. Some cancers affect just one organ, and others are more generalized.

In each of its types, however, cancer is characterized by the uncontrolled growth and spread of abnormal cells. Why cancer develops in some people who are exposed to potentially cancer-causing agents but not in others is not fully understood.

But what is known is that many cancers develop slowly. It may be 5 to 40 years after exposure to a cancer-causing agent before there is any evidence of the disease. Cancer of the lung, for example, may not appear until 25 years or more after sustained exposure to tobacco smoke.

This long delay between exposure and development of the disease may partly explain why so many people ignore the warnings associated with smoking. The Nutrition-Cancer Connection During the past 30 years, research has shown that nutrition plays a significant role in the development of many cancers and that proper food choices might help to reduce the risk of cancer or even prevent it.

About a third of the 500,000 cancer deaths that occur each year in the United States can be attributed to dietary factors. The good news is that in addition to engaging in regular exercise and not smoking, people have control over this important factor in cancer development—their food choices. Any number of dietary factors may be related to the risk of cancer.

Biology of Cancer

A biomedical revolution is advancing knowledge of the causes of cancer, yielding new and more effective treatments and inspiring greater hope for cancer prevention. This revolution is built on scientific investigation of the basic processes that cause cancer. The body is a living, growing system that contains billions of individual cells.

These cells carry out all of the body’s functions, such as metabolism, transportation, excretion, reproduction, and locomotion. The body grows and develops as a result of increases in numbers of new cells and their changes into different types of tissue.

New cells are created through the process of cell division (mitosis). Different types of cells are created by a process called cell differentiation, by which they acquire specialized function. Cell division results in the normal pattern of human growth; cell differentiation makes possible the normal, orderly pattern of growth and development.

Unlike normal cells, cancer cells lack the control mechanisms that stop, or “switch off,” growth. They divide without restraint, displacing neighboring normal cells, affecting their normal function and growth, and competing with them for available nutrients.

These uncontrolled cells can grow into a mass called a tumor and invade and destroy nearby normal tissue. They also can migrate in a process called “metastasis,” spreading via the blood or lymph system to other parts of the body. Not all cells that have rapid or uncontrolled growth are cancerous.

Cells may amass as benign tumors, which do not invade or destroy surrounding tissues. Although science has yet to understand the processes by which all cells grow, divide, communicate, and differentiate, much has been learned about how normal cells are activated or altered into cancerous cells in both inherited and noninherited forms of cancer.

Causes of Cancer

Cancer is caused by factors that are external (chemicals, radiation, viruses, and diet) and internal (hormones, immune and metabolic conditions, and inherited [genetic] alterations). Some of these factors are avoidable; others are not. Scientists have identified many of the controllable risk factors that increase the chances of getting cancer.

A complex mix of these factors, acting together or in some cascade of events, promotes cancer cell growth. When the genetic programming of a normal cell is disrupted, its malignant potential is released. Everyone carries this malignant potential within them in normal genes known as proto-oncogenes.

Products of these genes perform useful functions, such as regulating cell division and cell differentiation. These functions, however, may be compromised with aging or by exposure to cancer-causing (carcinogenic) agents. When this happens, they may be activated to become oncogenes, coordinating the conversion of normal cells to cancer cells.

Nutrition can influence any of the steps involved in the development of cancer. The development of cancer (carcinogenesis) and its relationship to nutrition is a complex process. Isolating and proving dietary cause-and-effect relationships can be difficult.

In addition, studies can be confusing and sometimes show conflicting results. Nevertheless, the potential for nutrition to increase or decrease the risk of various cancers is compelling.