Scientists have studied many foods and dietary components for possible associations with increasing or reducing cancer risk.
Credit: National Cancer Institute
Many studies have looked at the possibility that specific dietary components or nutrients are associated with increases or decreases in cancer risk. Studies of cancer cells in the laboratory and of animal models have sometimes provided evidence that isolated compounds may be carcinogenic (or have anticancer activity).
But with few exceptions, studies of human populations have not yet shown definitively that any dietary component causes or protects against cancer. Sometimes the results of epidemiologic studies that compare the diets of people with and without cancer have indicated that people with and without cancer differ in their intake of a particular dietary component.
However, these results show only that the dietary component is associated with a change in cancer risk, not that the dietary component is responsible for, or causes, the change in risk. For example, study participants with and without cancer could differ in other ways besides their diet, and it is possible that some other difference accounts for the difference in cancer.
When evidence emerges from an epidemiologic study that a dietary component is associated with a reduced risk of cancer, a randomized trial may be done to test this possibility. Random assignment to dietary groups ensures that any differences between people who have high and low intakes of a nutrient are due to the nutrient itself rather than to other undetected differences. (For ethical reasons, randomized studies are not generally done when evidence emerges that a dietary component may be associated with an increased risk of cancer.)
Scientists have studied many additives, nutrients, and other dietary components for possible associations with cancer risk. These include:
Excerpt from:
Risk Factors: Diet - National Cancer Institute
