Cruciferous vegetables—from the Cruciferae or Brassicaceae family—are nutritional standouts. Called cruciferous or crucifers because their flowers, if allowed to bloom, have four petals that form a cross (crux in Latin), these crunchy foods are loaded with nutrients. Indulge in some crucifers and you'll find vitamins such as C and folate, minerals such as potassium and varying amounts of calcium and iron, carotenoids like beta carotene, and fiber, as well as unique phytochemicals that may have potent anti-cancer effects—all for about 50 calories per cup.
What vegetables are crucifers? Cauliflower, cabbage, broccoli, bok choy, Brussels sprouts and some leafy greens (such as chard, collards, kale, watercress, and beet and mustard greens), as well as turnips, radishes, kohlrabi and rutabagas. Broccolini is a cross between broccoli and kale. Broccoflower (green cauliflower) is a cross between cauliflower and broccoli.
All crucifers have something to offer, so aim for variety. One cup of cooked, chopped broccoli, for instance, provides twice the daily requirement for vitamin C, about one-third as much beta carotene as a medium carrot, and nearly 10 percent of your daily calcium. Broccoflower has a little more beta carotene and vitamin C than white cauliflower; orange cauliflower has much more beta carotene than white. Purple cauliflower is loaded with antioxidants called anthocyanins. Kale and other leafy green crucifers are good sources of lutein and zeaxanthin for eye health.
What makes these veggies pungent or bitter? Sulfur-containing compounds called glucosinolates. When the vegetables are chopped or chewed, these compounds break down into isothiocyanates, indoles and other substances that are thought to have anti-cancer properties.
Studies find that high intakes of crucifers confer a reduced risk of bladder, colon, lung and other cancers. Also, lab research suggests that their phytochemicals help stop cancer initiation and slow its progression. For example, sulforaphane, a chemical that's abundant in broccoli, boosts production of enzymes that detoxify carcinogens, while inhibiting other enzymes that activate carcinogens. Crucifers may also protect against lung and heart disease and boost an aging immune system.
Ounce for ounce, the florets (or tender buds) have more beta carotene and, according to a 2006 study, nearly twice as much sulforaphane. The stalks, on the other hand, have more fiber. All parts of broccoli—even the leaves—are worth eating. Look for fresh broccoli with tight florets that are dark green or purplish (not yellowing).
It’s a toss-up. A recent study found that raw broccoli increased blood levels of sulforaphane more than cooked. But since many of these vegetables are not edible raw (or if you don’t like them that way), the key is to not overcook them (as in boiling until mushy), since that significantly reduces nutrients and phytochemicals and intensifies the sulfur smell. Try light steaming, quick stir-frying or microwaving, which do not cause significant losses. In addition, minimal cooking is enough to break down the plant’s cell walls and thus make antioxidants, such as carotenoids, more available.
Include these veggies, but know that they have drawbacks. Fermenting cabbage causes some nutrient losses, but the biggest problem with sauerkraut is its high sodium content (nearly 500 milligrams in half a cup). And coleslaw, typically made from shredded cabbage, is usually high in fat because it’s swimming in dressing. If you make your own, use low-fat mayonnaise or low-fat or nonfat yogurt.
Broccoli sprouts are the edible young shoots from broccoli seeds, similar to alfalfa sprouts. According to older research from Johns Hopkins, broccoli sprouts are “an exceptionally rich source” of sulforaphane, with 20 to 50 times as much as in mature broccoli. Scientists at Hopkins have gone so far as to develop a patented brand of broccoli sprouts, called BroccoSprouts. Broccoli sprouts have lower levels of other anti-cancer compounds, however, and they lack the full range of nutrients and fiber found in broccoli. Try broccoli sprouts (you can eat them raw on sandwiches or in salads), but don’t give up broccoli.
Why do crucifers cause bloating? The culprit is a complex sugar called raffinose, also found in beans, that bacteria in the large intestine feed on, releasing gas. Cooking does not help. If you’re not used to these vegetables, start slowly with small portions and gradually increase amounts. If you don’t tolerate them well, try eating small portions more often. Or try an enzyme product (such as Beano) that helps break down the sugar so it’s more digestible.
Broccoli extract pills are not a good substitute for the whole food. There are no studies in people showing that they reduce disease risk. Plus, they don’t contain all the healthful ingredients of the whole vegetables, which may work together for benefits. Some animal research even suggests that some compounds in extracts have potentially harmful effects, such as increased tumor promotion, if taken long term. Brassica Tea, a line of black, green and red bush teas, contains a broccoli extract. Like supplements, it’s not a substitute for broccoli.