The nutritional causes of colorectal cancer: an introduction to the Melbourne study

The Melbourne study has shown that dietary factors and alcohol are important in the cause and prevention of colorectal cancer (CRC). A high intake of fat and beef probably causes CRC, and a high intake of beer possibly causes rectal cancer. The beef and beer effects were both independent of other dietary variables, but further research is indicated to explore the mechanisms of their actions. Foods of plant origin protected against CRC, and the "plant food hypothesis" now replaces the dietary fiber hypothesis. Further study is needed on the interrelationships between various foods of plant origin. Vitamin supplements were protective, and again clarification is needed on the mechanism of action. In high-risk populations, nutritional risk and causal factors are likely to be difficult to find, whereas protective factors are likely to be found with greater ease. Further analysis of the Melbourne data will reveal the importance of diet in CRC causation, relative to the other hypothesized causal and protective factors.