A substance found in soybeans may reduce colon cancer risk, suggests animal research conducted by Alfred Merrill at Emory University and the Karmanos Cancer Institute.
The cancer-protective substance is a sphingolipid (a type of lipid or fat that, in the body, is primarily used as a constituent of nerve tissue) called soy glucosylceramide. Sphingolipids found in milk have already been shown to inhibit the formation of tumors in laboratory animals exposed to carcinogens known to cause colon cancer. While the sphingolipids found in soy differ structurally from those found in milk, the soy compounds had comparable effects.
When laboratory animals exposed to a carcinogen were given a diet containing 1% soy glucosylceramide, the proliferation of colon cancer cells dropped by 56%. When the same diet was given to a strain of animals bred to spontaneously develop colon cancer, the rate at which tumors formed dropped 37%.
Soy sphingolipids provided this protection by affecting the expression of 96 different genes in the cells that form the lining of the intestines, increasing 32 and decreasing 64. Soy's effects on these genes resulted in a decrease in the production of two factors associated with cancer initiation and promotion: hypoxia-induced factor 1 alpha and transcription factor 4.
While other plants also contain sphingolipids, soy contains relatively high amounts of glucosylceramide, which researchers think may be one reason for the cancer-preventive effects of eating soy foods.