A University of Missouri-Columbia researcher has shown that estrogen may protect against colon cancer, and that soy protein may help minimize the number and size of tumours that do occur.

Ruth MacDonald, professor of food science, fed female mice five different diets, and then followed their progress for a year. Diet one was made with milk protein, and diet two contained soy protein. Both diets were lacking any kind of estrogen. The other three diets contained soy protein with the addition of an estrogen component. Diet three contained soy protein and genistein, an estrogen-like compound found in soy. Diet four contained a commercial product with a mixture of soy-derived compounds including genistein, and diet five contained estrone, a naturally occurring human estrogen.

MacDonald found that while all the soy/estrogen diets gave some protection, the diet containing estrone was the most effective in preventing colon cancer. The researcher also discovered that those mice that ate soy protein and did develop colon cancer had fewer and smaller tumours than those mice that did not eat soy protein.

“We know that soy protein may be helpful in the prevention of heart disease, but this work suggests it may also be beneficial in the prevention and control of colon cancer. The good news is that there are many ways to add soy to your diet now and we know of no harmful side-effects to eating soy protein.”

University of Missouri-Columbia, Feb 4, 2004