Headlines that announce another study in which a common fruit or vegetable reduces the incidence of  cancer are becoming more and more common. This is happening as scientists are able to detect, isolate and concentrate minor constituents of foods that have anti-cancer properties. At the same time our understanding of how cancer develops and spreads is expanding. The development of cancer can be divided into several related but distinct stages. At each stage it appears that consumption of certain foods or food ingredients can slow or reverse the cancer.

Food or food ingredients  can act to suppress, block or to transform agents that can cause cancer. In the normal course of digestion and metabolism, compounds that start out as being safe and nutritious can be converted to procarcinogens or compounds  that have been shown to be capable of causing cancer. A food or food ingredient that prevents this conversion is called a suppressor.  Antioxidents such as vitamin C and vitamin E would be examples of  suppressors as they prevent the formation of free radicals that have been shown to cause cell damage that can lead to many cancers.

When procarcinogens are formed, they  have to be transported to the organ or tissue where they then attack  healthy cells and start the growth of the cancer. Some compounds, termed blockers, have been shown to be able to prevent the procarcinogens from locating where they can do their damage. The blocker reacts with the procarcinogen forming a product that can be quickly excreted from the body before it can become established.

Agents that act as transformers act in a similar way to blockers. Transformers  are able to react with or metabolize the procarcinogen into nontoxic products. Some blockers are enzymes systems that occur naturally in the body and are capable of  metabolizing a wide range of  compounds. The activity of these enzymes can be increased by changes in the diet, and this can provide protection when the body is exposed to procarcinogen or carcinogens.

Once a cancer has become established the cells that it has invaded lose their ability to stick together. The infected cells are then able to break away and circulate throughout the body via  the blood and lymph  systems. The appearance of cancer in organs and tissues distant from the initial site of disease results. Some food ingredients such as the flavones in orange,tangerine and grapefruit have been shown to be able to restore the adhesion between cells  that would prevent the spread of cancer cells in the body.

The many factors that cause cancer and allow it to grow and spread in the body are not all well understood. But it is becoming more and more evident that many foods contain components that can act against cancer cells at very particular stages of cancer initiation, growth, development and spread.