The globe artichoke, also known by the names French artichoke and green artichoke, is a variety of thistle cultivated as food. The edible portion of the plant consists of the flower buds before the flowers come into bloom. The budding artichoke flower-head is a cluster of budding small flowers, together with many bracts, on an edible base. Once the buds bloom, the structure changes to a coarse, barely edible form. Artichokes are frequently prepared by removing all but 5–10 mm of the stem. To remove thorns, which may interfere with eating, around a quarter of each scale can be cut off. To cook, the artichoke is boiled or steamed. A cooked, unseasoned artichoke has a delicate flavour. Salt may be added to the water if boiling artichokes. Placing them in water slightly acidified with vinegar or lemon juice can prevent the discoloration. Artichokes have a high antioxidant content that may help prevent cancer, manage weight, and control blood sugar and diabetes. They are a good source of fiber and other nutrients. In addition, artichoke nutrition contains some vitamin A, vitamin E, choline, betaine, omega-3 and omega-6.