Research into colorectal cancer is hampered by the fact that studies must take a very long time to produce results and be very large if the development of a cancer is the endpoint. Therefore alternative methods of quantifying the risk of developing a cancer are required so trials can be a realistic size and be completed in a realistic time frame. The investigators have previously identified several candidates for these 'biomarkers'. The next stage in proving or disproving these as useful biomarkers is to test their response to a dietary agent that the investigators know reduces the risk of colon cancer.