Garlic: A Review of Its Medicinal Effects and Indicated Active Compounds

Abstract

Numerous clinical trials with garlic cloves and standardized garlic powder tablets leave little doubt that modest amounts of garlic have significant cardiovascular effects by reducing serum cholesterol, blood pressure, and platelet aggregation. Epidemiological and animal studies strongly indicate significant anticancer effects, particularly for the intestinal tract. Furthermore, its intestinal and topical antimicrobial activities have been its longest recognized effects. Identification of the compounds essential to the activity of garlic, mostly ascribed to its high content of sulfur compounds, has only been partially resolved. So far, the thiosulfinates, of which allicin is 70-80%, are the only compounds with reasonably proven activity at levels representing normal amounts of garlic consumption. They are clearly responsible for the antimicrobial effects. Several evidences also indicate that they are essential to most of the hypolipidemic, antithrombotic, antioxidant, and hypoglycemic effects of garlic, and for some of its anticancer effects. However, because the thiosulfinates are rapidly metabolized and since their active metabolites have not yet been identified, little is known about their mechanism of action. The compounds responsible for the hypotensive effects and much of the anticancer and immune effects of garlic remain unknown. Until they are known, it is best to consume garlic in whole form, fresh or dried.