It is possible to affirm that, with certainty, in the coming decade, cancer will be the first cause of death in countries with medium or high development. The main reason that justifies this affirmation can be found in the sustained increase in survival observed in these countries, fundamentally due to an improvement in the living conditions of the population and the undoubted medical progress. Cancer development is a long-term process produced by the accumulation of genomic damage, which is why the increase in survival works in its favour.
Data generated globally in recent decades show that eating habits, smoking, exposure to occupational pollutants and infection constitute a significant percentage of the causes of risk of contracting cancer. In this way, lifestyles, an essentially reversible causal element, have become the subject of intense research and are currently predominant factors in cancer prevention. This was suggested in the class today sic work by Doll and Peto of 1981, which, to date, remains valid.
How is the nutritional factor capable of modulating tumour development?
In different ways. An element associated with a diet that has shown a relevant impact on cancer prevention is the decrease in caloric intake (calorie restriction), which has also been shown to have a significant effect on life extension. This statement is based on the recognised fact that tumour cells have a demanding metabolic requirement for their proliferation and growth and that, in addition, they show a worse adaptation to a restrictive caloric regimen compared to a normal cell. Research carried out in experimental animals, and human observational studies have reaffirmed this option.
On the opposite side, we find the case of obesity.
This pathology is attributed to responsibility for a growing percentage of cancer mortality, and that has promoted both weight loss and a physical exercise regimen to become practical preventive elements of neoplastic disease. Not all forms of cancer are equally affected by obesity; however, the most recent data suggest that obesity is a critical risk factor for at least 13 types. By the way, the mechanisms by which obesity affects carcinogenesis may be different; the influence of obesity on colon cancer is not the same as on breast cancer. However, it seems that the systemic inflammatory phenomenon that generates obesity is at the base of the development of many forms of cancer.
Is there a diet that prevents or enhances tumour development?
Here the answer is less definite, fundamentally, because the generic recommendation of a healthy diet typically entails a decrease in caloric intake, which can put that recommendation under the category mentioned above of caloric restriction. However, there are examples of types of food that -according to the evidence- would have a responsibility in the development of some types of cancer. This is the case of the consumption of red meat associated with colorectal cancer. Consistent epidemiological data show that this type of tumour is highly prevalent in countries that are high consumers of red meat, as is the case in Uruguay. The association between the high incidence of gastric cancer in Japan (and also China) has been attributed to the consumption of salty foods that contain nitrosamines, either endogenously or produced during cooking. These compounds increase their carcinogenic potential in the presence of salt. It has been proposed that this interaction results from culinary practices typical of these countries. However, other highly prevalent factors, such as infection with Helicobacter Pylori and the widespread smoking habit in this population, make the association of dietary factors with gastric cancer somewhat less evident. Excessive alcohol consumption has also been associated with various forms of cancer, such as oral cavity, pharynx, oesophagus, colon, liver, larynx, and breast in women.
The possibility of a protective diet against cancer has pointed to the high consumption of fruits and vegetables. In studies that include large populations of consumers, it has been found that a diet rich in vegetables prevents the appearance of a wide range of cancers in humans. There is also a certain consensus that more than a specific component of the diet rich in vegetables, it is the synergistic combination of many of them that act as a protective element.
In summary, the accumulated evidence supports that a growing percentage of tumours in adults can be prevented by maintaining a healthy lifestyle that includes nutrition, exercise and fitness, and avoiding harmful habits of tobacco and alcohol consumption.