First, you IBS is probably not tied to these foods. Also, not to be a nit-picker, but corn is a grain, not a vegetable, and zucchini is a fruit, also not a vegetable. The importance of this is in both your IBS and the nutrients you might not be getting by not eating true vegetables. Corn can be a troublesome food for many, as it's a common allergen and also contains a lot of sugar. Carrots are great cooked and raw -- cooked they have more carotenoids, raw more fiber.