Garlic has long been used in cooking and in medicine. When a garlic bulb is cut or crushed, an amino acid byproduct called allicin is released. Allicin is responsible for garlic’s strong odor and medicinal properties.
Garlic reduces the normal clotting tendency of particles in the blood that help stop bleeding (platelets). Because garlic stops microorganisms (such as bacteria) from reproducing, it can be used as an antiseptic and antibacterial. In large doses, garlic can slightly reduce blood pressure, overactivity of the intestine, and blood sugar levels. Advocates suggest that garlic lowers levels of low-density lipoprotein (LDL)—the bad—cholesterol. However, at least one well-designed study did not support this beneficial effect. Most studies have used aged garlic extracts. Preparations formulated to have little or no odor may be inactive and need to be studied.
Garlic usually has no harmful effects other than making the breath, body, and breast milk smell like garlic. However, consuming large amounts can cause nausea and burning in the mouth, esophagus, and stomach.
Garlic may interact with drugs that prevent blood clots (such as warfarin), increasing risk of bleeding. Thus, garlic should not be eaten or taken as a supplement 1 week before surgery or before a dental procedure.