The Green Group includes broccoli, arugula, brussel sprouts, Chinese cabbage, Bok Choy, and Horseradish. When you bite into these vegetables you release a chemical called Isothiocyanate, which is a poison with a sharp bitter taste. It is stored in the plant as glucosinolate, which is harmless. When you or a small animal bites into the plant, an enzyme called myrosinase breaks down the glucosinolates to release the poisonous isothiocyanate. In Peru, the Incas would plant broccoli around their potatoes to keep guinea pigs from eating the potatoes. The poison activates a family of enzymes on your liver that protect you from many other toxins in the foods you eat. This is an example of "what doesn't kill you makes you stronger!" This primitive defense mechanism found in 450 different plant species helps our defenses against toxic substances in our diet. Research supports eating vegetables from this group at least three times per week.