Protocol for a study of nutritional factors and the low risk of colon cancer in Southern retirement areas.

Colon cancer shows a distinct geographic pattern in the United States, with mortality rates in the Northeast exceeding those in the South by about 50%. The North-South gradient remains even after adjustment for differences in urbanization and socioeconomic status. Those counties in the South that attract large numbers of retirees from the North retain the low colon mortality rates characteristic of the South, even at older ages. This observation implies either that certain life-style changes associated with migration at retirement rapidly reduce the risk of colon cancer or that individuals migrate selectively, based on some correlate of health. A specific hypothesis related to the former possibility is that consumption of fruits and vegetables, and the associated vitamin C, carotene, and fiber, is elevated in the South and related to the reduced risk of colon cancer. A protocol is presented for a case-control interview study in Southern retirement areas to assess these possible explanations. A detailed residential history, as well as information on frequency of consumption of specific foods, food groups, and micronutrients, will be collected by interview and will be complemented by selected serum micronutrient determinations and fecal mutagenicity assays.