Cancer is the second leading cause of death in the US, killing 1 in 4 Americans each year. Diet may be linked to as much as one-third of cancer deaths, and components in plants called phytochemicals may decrease cancer risk. Garlic contains the phytochemical allicin which may reduce cancer risk by helping enzymes destroy cancer-causing substances. The document recommends including garlic in your diet several times per week to help decrease cancer risk.