Diet and cancer

 Obesity increases the risk of developing cancer. Particular dietary practices often explain differences in cancer incidence in different countries (e.g. gastric cancer is more common in Japan, while colon cancer is more common in the United States). Studies have shown that immigrants develop the risks of cancer predominant in their new country, suggesting a link between diet and cancer.

 Despite frequent reports of particular substances (including foods) having a beneficial or detrimental effect on cancer risk, few of these have an established link to cancer. These reports are often based on experiments on animals.

 Epidemiologists studying diet habits observed that high levels of beta-carotene, a precursor to vitamin A, were associated with a protective effect, reducing the risk of cancer. This phenomenon was particularly strong in lung cancer.