Confirmatory Evidence of Cancer-Nutrition Link Remains Elusi... : Oncology Times
Confirmatory Evidence of Cancer-Nutrition Link Remains Elusive
SAN FRANCISCO-Although a link between nutrition and cancer was posited as long ago as ancient China, modern studies have been only partly successful in illuminating this association, explained Arthur Schatzkin, MD, DrPH, of the NCI's Nutritional Epidemiology Branch, speaking here at the American Society of Clinical Oncology Annual Meeting at a Scientific Symposium on Nutrition and Cancer.
Do we have hard, credible evidence that nutritional modification can truly affect the incidence of malignant disease in humans? The answer, in short, is a resounding maybe. We are getting there, but nutrition and cancer is a complex and difficult field. When it comes to nutrition, the evidence is softer and vulnerable to the results of the latest analysis or published paper.
The dearth of hard evidence coupled with inherent difficulties in conducting valid studies in this area has led to confusion and inconsistency about the role of nutrition in the risk of developing cancer.
Obstacles to conducting studies of nutritional epidemiology of cancer cited by Dr. Schatzkin include: exposure assessment error (is the right dietary factor being studied and are the right questions being asked?), inadequate range of exposure (many populations have narrow intake distributions for certain potentially cancer-related nutrients and foods), and confounding (people who follow a certain type of diet may also differ in biologic or lifestyle factors that are related to the risk of developing cancer).
Randomized, controlled trials largely circumvent the problem of confounding, and results from such studies are extremely compelling, Dr. Schatzkin continued. However, these studies are expensive and logistically complex to mount.
At present, Dr. Schatzkin said it is difficult to make recommendations with certainty regarding controversial areas such as the relationship of dietary fat intake and breast cancer; the role of dietary fiber and colorectal cancer; and the role of vitamins/supplements (i.e., beta carotene and lung cancer, lycopene, and prostate cancer, and folic acid and colorectal cancer). The hope is that future studies will help to resolve these issues.