Cancer risk factors in human studies.

The historical developments leading to the acceptance of the influence of dietary and behavioral aspects of our life-style on cancer are reviewed. However, present information is usually insufficient to permit description of the complex mechanisms involved that are unlikely to yield to classical epidemiologic approaches alone. Better integrated laboratory epidemiologic studies are required that use more advanced nonintervention techniques. Progress may be slow in the identification of such factors in view of the many parameters involved, the absence of a single predominant or avoidable cause in many cancers, and the lack of adequately developed laboratory techniques for epidemiologic application.