Add a Little Flavor to Your Life
By: Clinical Nutrition Department, M. D. Anderson Cancer Center

Garlic is a great spice for adding flavor to your favorite dishes. It is a relative of the leek, onion, and other related spices with the aromatic sulfur based compounds that give the characteristic odor and taste. The bulbs of these plants have been used for centuries as a remedy for numerous medical afflictions. More recently garlic has been used for the prevention and treatment of atherosclerosis (hardening of the arteries), hypertension (high blood pressure), and cancer.

Health Claims

The research regarding garlic's anticancer properties is inconclusive. There is some evidence indicating that garlic may enhance immune function, act as an antioxidant by increasing enzyme activity that blocks carcinogens, and inhibit the growth of malignant cells. Epidemiological studies in China and Italy found fewer cases of stomach cancer among those who consumed vegetables, such as garlic, onions, leeks, and shallots, than among those who consumed little or none of these foods. However, the questionable design of those studies makes conclusions impossible. Animal studies have found that garlic compounds can inhibit many types of cancer including lung, breast, skin, colon, and esophageal. Garlic may also lower LDL cholesterol (bad cholesterol) and triglycerides and raise HDL cholesterol (good cholesterol). It is important to remember, however, that none of the research on garlic's anticancer properties has been done in individuals with genetic cancer predispositions. Thus, more research will need to be done to determine if garlic protects against cancer in individuals with conditions such as HNPCC and FAP.

Precautions

Because of their ability to inhibit platelet aggregation (blood clot formation), garlic supplements should be avoided by those taking aspirin or anticoagulants and those who have other health problems that affect blood coagulation. Heat and acid destroy allicin, the compound in garlic thought to be responsible for garlic's pharmacological activities. Too much garlic may cause nausea, vomiting, flatulence, decreased blood glucose, heartburn, and body/breath odor.

Dose

For prevention of heart disease, several sources recommend garlic supplements that are coated to allow their passage through the stomach before digestion. Such supplements usually contain 4000 milligrams of garlic standardized to an allicin yield of at least 5000 milligrams daily, the equivalent of about one clove of fresh garlic. The dose required for cancer protection is unknown at this time. One warning, however: heating garlic in the peel destroys the enzyme that activates garlic's potential anticancer compounds. Animal studies indicate that peeling the garlic clove and waiting 15 minutes before cooking it will activate the enzyme and allow it to work.