Cancer is a disease of genes, which are vulnerable to beneficial and harmful mutations, especially over the long human lifespan. Nutritional factors are important in determining the likelihood of some mutations, as well as in changing gene function even without mutation. Epidemiological and experimental evidence demonstrate that only a small proportion of cancers are inherited; environmental factors are the most important cause of genetic modification. These factors include smoking, infectious agents, radiation, industrial chemicals and pollution and medication. Nutrition, physical activity and body composition can also play a role. Essentially this is good news. It means that a healthy lifestyle can stop cancer before it starts.

In this context, nutrition represents an extraordinary tool to prevent cancer. It is already known that being overweight or obese increases the cancer risk; a healthy diet could reduce this. Furthermore, there is evidence to indicate that bioactives in the diet play an important role in promoting health. Validating health effects of foods and food components represents the new target of nutrition research together with understanding mechanisms through which diet factors could prevent disease.
However, healthy nutritional guidelines are partially known and poorly practiced, others could be established and implemented.