Brassica vegetables are members of the Brassica genus of plants and include the related plants broccoli, cauliflower, and kale. Cabbage, Brussels sprouts, and turnips are also part of this group. These vegetables are low in calories and are generally very nutritious, especially green brassica vegetables such as broccoli, kale, and Brussels sprouts. These plants in particular are excellent sources of vitamins A and C and also provide some of the B vitamins and some necessary minerals. Other members of this group of vegetables are collard and mustard greens as well as bok choy.
Being made mostly of water, brassica vegetables are excellent sources of nutrition considering the few calories they contain. Cooked servings of these vegetables usually have only about 30 or fewer calories. This makes them a good choice not only for reduced-calorie diets, but also for most diets in general. They contain very little fat, with the calories coming from carbohydrates and protein. Many are also good sources of fiber.
Green vegetables in this group are a good source of vitamin A in the form of beta carotene. One half cup of cooked broccoli contains about 25 percent of the recommended daily allowance (RDA) for vitamin A. About 3.5 ounces (100 g) of cooked kale provides more than 250 percent of the RDA for vitamin A, which is a safe amount when taken as beta carotene from food sources. Brussels sprouts and cabbage provide good but smaller amounts of beta carotene. Eating these vegetables with olive oil or dressing that contains a little fat improves the body's ability to use beta carotene.
Some of the brassica vegetables, such as broccoli and cauliflower, contain vitamin C in amounts similar to citrus fruits. A little less than 3 ounces (about 78 g) of cooked broccoli or Brussels sprouts offers about 80 percent of the RDA for vitamin C. One half cup of cooked cauliflower provides about 50 percent of the RDA for this vitamin, and 3.5 ounces (100 g) of cooked kale provides about 70 percent.
Green plants in the brassica vegetables group are also good sources of folate and excellent sources of vitamin K. Folate is an important B vitamin that is also present in other green vegetables. Green brassica vegetables are also fair sources of vitamin E, a vitamin that is otherwise mostly found in nuts and seeds.
A fair amount of potassium can be obtained from a serving of most brassica vegetables, especially the green vegetables in this group. A cooked serving of kale, Brussels sprouts, or broccoli contains about 8 percent of the RDA for potassium. They also contain some iron, calcium, and magnesium. Cauliflower and turnips, on the other hand, provide less potassium and fewer minerals in general.