Scientists recognise that many cancers can be prevented by modifying what people eat and their level of physical activity. To this end, the World Cancer Report Fund and the American Institute for Cancer Research produced a report in 2007 identifying the preventable causes for many cancers. This report provides strong evidence for ascribing cancers to certain substances in the environment as well as the level of physical activity.
Cancer of the lung is the chief cause of cancer death worldwide. Three-quarters of lung cancers occur in men. It is almost always fatal. The principal cause of this cancer is smoking tobacco. So lung cancer is prevented by not smoking either actively or passively. Arsenic in drinking water and beta-carotene supplements actually increase the risk of this cancer in smokers.
Prostate cancer is the sixth most common cause of death in men worldwide. As screening becomes more available, more men present with this condition. The report highlights the probable link between men with diets high in calcium and prostate cancer. There is limited evidence that processed meats, milk and dairy products are a cause of prostate cancer. On the other hand, foods containing lycopene (such as cooked tomatoes), legumes, soya, soya products, and foods containing vitamin E are likely to be protective against prostate cancer.
Stomach cancer is the second most common cause of cancer deaths worldwide. In Jamaica, the rate of this cancer is lessening as our economy grows. Salt and salt-preserved foods are probable causes while infection with Helicobacterium pylori is recognised as the cause. Carcinogens are also produced in the stomach from nitrates in foods. These environmental factors plus ageing and hereditary factors result in changes in the stomach lining leading to gastritis and stomach cancer. Non-starchy vegetables, fruits, allium vegetables (garlic), legumes and foods with selenium probably protect against stomach cancer.
Cancers of the colon and rectum are the cause of a fourth of all cancer deaths worldwide. It is relatively uncommon in Africa and Asia but increases as a country becomes more industrialised. Men are more likely than women to develop this cancer. There is evidence that the risks of these cancers increase with the intake of red meat, processed meat and alcoholic drinks.
Men who are obese, especially with increased abdominal fat are at increased risk of colon and rectal cancer. There is convincing evidence that physical activity protects against these cancers, in particular, colon cancer. Foods containing dietary fibre, as well as garlic, milk and calcium are probably protective.
There is overwhelming evidence that the following recommendations will reduce the risk of cancers in the population:
1. Be as lean as possible within the normal range of body weight.
2. Be physically active as part of everyday life.
3. Avoid sugary drinks.
4. Eat mostly foods of plant origin.
5. Limit intake of red meat and avoid processed meat.
6. Limit alcoholic drinks.
7. Avoid smoking.
8. Limit consumption of salt.