The potato is a perennial plant of the Solanaceae, or nightshade, family, grown for its starchy tuber. Potato plants have a low-growing habit and bear white to purple flowers with yellow stamens. In recent centuries potatoes have become the world's most important tuber crop and its fourth most important source of food energy (after rice, wheat, and maize): farmers and gardeners grow them worldwide. Potatoes are often broadly classified as “high” on the glycemic index (GI) and; thus, are frequently excluded from the diets of individuals trying to follow a “low GI” eating regimen. In fact, the GI of potatoes can vary considerably depending on the type (i.e., red vs. russet vs. white vs. Prince Edward), origin (i.e., where it was grown), preparation methods (i.e., cooking method, whether it is eating hot or cold, whether it is mashed or cubed or consumed whole, etc), and what it is consumed with (i.e., the addition of various high fat or high protein toppings). Potatoes contain glycoalkaloids, toxic compounds, of which the most prevalent are solanine and chaconine. Cooking at high temperatures partly destroys these.