A diet high in fast food is associated with both greater meat consumption and reduced milk consumption - increased consumption of red and processed meat has been shown to increase risk of cancers of the distal colon and rectum, while milk and calcium consumption have shown a protective effect against the subsites in which the rise in incidence was most prominent.

The researchers say it is possible that the emergence of unfavourable dietary patterns in children and young adults over the past three decades may have contributed to the increase in colorectal cancer rates among young adults and they suggest that the disparate increase in left-sided colorectal cancers warrants particular attention be given to studies to elucidate the behavioral and environmental risk factors responsible for this trend and potential prevention and early detection strategies.

The study appears in the June 2009 issue of Cancer Epidemiology Biomarkers and Prevention.