Cooking protein-rich foods like meats and eggs at high temperatures releases a chemical called PhIP, which is thought to be cancer-causing.It could be behind the link between increased incidence of breast cancer among women who eat large quantities of meat, although fat and caloric intake and hormone exposure may also play a role in this increased risk.
Diallyl sulphide (DAS), a flavour component of garlic, has been shown to inhibit the effects of PhIP that, when biologically active, can cause DNA damage or transform substances in the body into carcinogens.
Ronald Thomas and a team of researchers at Florida A&M University in Tallahassee suspected that PhIP enhances the metabolism of the enzymes linked to carcinogenesis. They tested whether diallyl sulphide derived from garlic could counter this activity.
"We treated human breast epithelial cells with equal amounts of PhIP and DAS separately, and the two together, for periods ranging from three to 24 hours," said Thomas, presenting the study at the American Association for Cancer Research's Frontiers in Cancer Prevention Research meeting in Baltimore (abstract 2543).
"PhIP induced expression of the cancer-causing enzyme at every stage, up to 40-fold, while DAS completely inhibited the PhIP enzyme from becoming carcinogenic."
The finding demonstrates for the first time that DAS triggers a gene alteration in PhIP that may play a significant role in preventing cancer, notably breast cancer, induced by PhIP in well-done meats.
Consumption of garlic, chives, and other allium vegetables has previously been associated with a reduced risk of prostate cancer too.