Diet, folate, and colon cancer.

Evidence emerging from many different types of experimental designs continues to support the concept that dietary habits and nutritional status play important roles in determining the risk of colorectal cancer. This field of investigation is nevertheless very confusing, particularly because longstanding hypotheses, such as the presumed protective effects of fruits, vegetables, and fiber, have recently been challenged by well-designed prospective trials. The search for individual components in the diet that convey protection continues: calcium, folate, selenium, and omega-3 fatty acids are the leading candidates in this regard. There is also growing interest in other plant-based compounds, so-called phytochemicals, although our understanding of their effects is quite rudimentary at present. Although the inconsistencies in this field make it tempting to minimize its import, there is little question that diet has a major impact on colorectal cancer risk; diligent attention to the rigorous conduct of studies and their interpretation will likely clarify these relationships over the next decade, much to the benefit of public health.