Scientists have proved a link between high-fat diets and colon cancer, an association long-suspected by researchers.

Molecular scientists are discovering a complicated interaction between genetic and environmental factors which is certainly the cause of colon cancer, and which may point the way to other malignancies as well.

It would also explain why some members of the same family, presumably eating the same diet, are more susceptible to cancer than others.

Scientists from the Jefferson Cancer Institute in Philadelphia have discovered that the difference may lie in "modifier" genes; their interaction with mutant genes can determine whether someone will develop cancer or not. The modifier genes and a gene that instructs intestinal cells to produce an enzyme involved in fat digestion were the same.

The scientists hypothesized that high levels of the enzyme in the intestine in some way counter potentially harmful effects of dietary fatty acids.

Their findings tie in with earlier research showing that diets with a high saturated fat content are linked to intestinal anaerobic bacteri, which are suspected of producing toxins that encourage polyp formation and increase tumour growth.

Scientists have also discovered that other cancers such as cancers of the lung and bladder have patterns of repetitive "junk" DNA, which may serve as a marker for malignancies (JAMA, August 2, 1995).