What foodstuffs contain zero calories?

Zero or neg. calorie: Zero or negative calorie foods don’t lack calories, but they require more calories to digest than are consumed. Some examples include lettuce, onions, peppers, radish, spinach, turnips, zucchini, garlic, cucumbers, dandelions, endive, asparagus, beet roots, green cabbage, cauliflower, celery, cress, leeks, green beans, grapefruits, cantaloupe, rhubarb & honeydew melon.