Vegetables, fruits, and colorectal cancer risk: what should we believe?

Among dietary factors implicated in the development of colorectal cancer (CRC), the inverse relationship between vegetable and fruit consumption and CRC risk has long been believed to represent the strongest epidemiologic evidence. However, recently published large prospective studies have produced conflicting results and the results of one randomized intervention human trial do not support the protective role of vegetable and fruit consumption in colorectal carcinogenesis. Conflicting data with regard to the effect of dietary factors, including vegetables and fruits, on CRC risk likely reflect inherent, probably irresolvable, limitations of currently available tools to detect a real beneficial or harmful effect associated with these factors.