Case‐control study of dietary etiological factors: The Melbourne colorectal cancer study

Abstract

As part of a large‐scale investigation of colorectal cancer (CRC) incidence, etiology, and survival, a case‐control study was conducted to identify dietary factors associated with the risk of CRC. The study compared 715 cases with 727 age‐ and sex‐matched community controls. A quantitative diet history, assessed to be the most representative of the previous 20 years, was obtained from each subject and analyzed for both food groups and nutrients. The combination of a high‐fiber and high‐vegetable intake was found to be protective against large bowel cancer. Cruciferous vegetable intake was also found, although with less certainty, to be protective. Dietary vitamin C was protective for estimated intakes greater than 230 mg/day. Dietary β‐carotene had no separate association with the risk of CRC. Beef intake was a risk factor in males but not in females. Fat intake was a risk factor for both males and females. A low intake of milk drinks was a risk for both males and females. A high intake of pork and fish was protective. The use of vitamin supplements was highly protective. A risk score, which was calculated as the number of risk factors an individual has in his or her diet, showed an increasing mono‐tonic relationship with risk of CRC. The effects of the dietary variables were similar for colon and rectal cancer and, with the exception of beef, were similar for males and females.