(Bok choy [Chinese cabbage], green cabbage, red cabbage, savoy cabbage)
See also Broccoli, Brussels sprouts, Cabbage, Cauliflower, Lettuce, Radishes,
Energy value (calories per serving): Low
Saturated fat: Low Cholesterol: None Carbohydrates: High
Major vitamin contribution: Vitamin A, folate, vitamin C
Major mineral contribution: Calcium (moderate)
About the Nutrients in This Food
All cabbage has some dietary fiber food: insoluble cellulose and lignin in the ribs and structure of the leaves. Depending on the variety, it has a little vitamin A, moderate amounts of the B vitamin folate and vitamin C.
One-half cup shredded raw bok choy has 0.1 g dietary fiber, 1,041 IU vitamin A (45 percent of the R DA for a woman, 35 percent of the R DA for a man), and 15.5 mg vitamin C (21 percent of the R DA for a woman, 17 percent of the R DA for a man).
One-half cup shredded raw green cabbage has 0.5 g dietary fiber, 45 IU vitamin A (1.9 percent of the R DA for a woman, 1.5 percent of the R DA for a man), 15 mcg folate (4 percent of the R DA), and 11 mg vitamin C (15 percent of the R DA for a woman, 12 percent of the R DA for a man).
One-half cup chopped raw red cabbage has 0.5 g dietary fiber, 7 mcg folate (2 percent of the R DA), and 20 mg vitamin C (27 percent of the R DA for a woman, 22 percent of the R DA for a man).
One-half cup chopped raw savoy cabbage has one gram dietary fiber, 322 IU vitamin A (14 percent of the R DA for a woman, 11 percent of the R DA for a man), and 11 mg vitamin C (15 percent of the R DA for a woman, 12 percent of the R DA for a man).
Raw red cabbage contains an antinutrient enzyme that splits the thiamin molecule so that the vitamin is no longer nutritionally useful. This thiamin in hibitor is inactivated by cooking.
The Most Nutritious Way to Serve This Food
Raw or lightly steamed to protect the vitamin C.
Diets That May Restrict or Exclude This Food
Buying This Food
Look for: Cabbages that feel heavy for their size. The leaves should be tightly closed and attached tightly at the stem end. The outer leaves on a savoy cabbage may curl back from the head, but the center leaves should still be relatively tightly closed.
Also look for green cabbages that still have their dark-green, vitamin-rich outer leaves.
Avoid: Green and savoy cabbage with yellow or wilted leaves. The yellow carotene pig- ments show through only when the cabbage has aged and its green chlorophyll pigments have faded. Wilted leaves mean a loss of moisture and vitamins.
Storing This Food
Handle cabbage gently; bruising tears cells and activates ascorbic acid oxidase, an enzyme in the leaves that hastens the destruction of vitamin C.
Store cabbage in a cool, dark place, preferably a refrigerator. In cold storage, cabbage can retain as much as 75 percent of its vitamin C for as long as six months. Cover the cabbage to keep it from drying out and losing vitamin A.
Preparing This Food
Do not slice the cabbage until you are ready to use it; slicing tears cabbage cells and releases the enzyme that hastens the oxidation and destruction of vitamin C.
If you plan to serve cooked green or red cabbage in wedges, don’t cut out the inner core that hold the leaves together.
To separate the leaves for stuffing, immerse the entire head in boiling water for a few minutes, then lift it out and let it drain until it is cool enough to handle comfortably. The leaves should pull away easily. If not, put the cabbage back into the hot water for a few minutes.
What Happens When You Cook This Food
Cabbage contains mustard oils (isothiocyanates) that break down into a variet y of smelly sulfur compounds (including hydrogen sulfide and ammon ia) when the cabbage is heated, a reaction that occurs more strongly in aluminum pots. The longer you cook the cabbage, the more smelly the compounds will be. Adding a slice of bread to the cooking water may lessen the odor. Keeping a lid on the pot will stop the smelly molecules from floating off into the air, but it will also accelerate the chemical reaction that turns cooked green cabbage drab.
Chlorophyll, the pigment that makes green vegetables green, is sensitive to acids. When you heat green cabbage, the chlorophyll in its leaves reacts chemically with acids in the cabbage or in the cooking water to form pheophytin, which is brown. The pheophytin gives the cooked cabbage its olive color.
To keep cooked green cabbage green, you have to reduce the interaction between the chlorophyll and the acids. One way to do this is to cook the cabbage in a large quantity of water, so the acids will be diluted, but this increases the loss of vitamin C.* Another alternative is to leave the lid off the pot so that the volatile acids can float off into the air, but this allows the smelly sulfur compounds to escape too. The best way may be to steam the cabbage ver y quickly in ver y little water so that it keeps its vitamin C and cooks before there is time for the chlorophyll/acid reaction to occur.
Red cabbage is colored with red anthocyanins, pigments that turn redder in acids (lemon juice, vinegar) and blue purple in bases (alkaline chemicals such as baking soda). To keep the cabbage red, make sweet-and-sour cabbage. But be careful not to make it in an iron or aluminum pot, since vinegar (which contains tannins) will react with these metals to create dark pigments that discolor both the pot and the vegetable. Glass, stainless-steel, or enameled pots do not produce this reaction.
How Other Kinds of Processing Affect This Food
Pickling. Sauerkraut is a fermented and pickled produce made by immersing cabbage in a salt solution strong enough to kill off pathological bacteria but allow beneficial ones to sur- vive, breaking down proteins in the cabbage and producing the acid that gives sauerkraut its distinctive flavor. Sauerkraut contains more than 37 times as much sodium as fresh cabbage (661 mg sodium/100 grams canned sauerkraut with liquid) but only one third the vitamin C and one-seventh the vitamin A.
* According to USDA, if you cook t hree cups of cabbage in one cup of water you will lose only 10 percent of t he vitamin C; reverse t he rat io to four t imes as much water as cabbage and you will lose about 50 percent of t he vitamin C. Cabbage will lose as much as 25 percent of its vitamin C if you cook it in water t hat is cold when you start. As it boils, water releases ox ygen t hat would ot her wise dest roy vitamin C, so you can cut t he vitamin loss dramat ically simply by lett ing t he water boil for 60 seconds before adding t he cabbage.
Medical Uses and/or Benefits
Protection against certain cancers. Naturally occurring chemicals (indoles, isothiocyanates, glucosinolates, dithiolethiones, and phenols) in cabbage, brussels sprouts, broccoli, cauli- flower, and other cruciferous vegetables appear to reduce the risk of some cancers, perhaps by preventing the formation of carcinogens in your body or by blocking cancer-causing substances from reaching or reacting with sensitive body tissues or by inhibiting the trans- formation of healthy cells to malignant ones.
All cruciferous vegetables contain sulforaphane, a member of a family of chemicals known as isothiocyanates. In experiments with laboratory rats, sulforaphane appears to increase the body’s production of phase-2 enzymes, naturally occurring substances that inac- tivate and help eliminate carcinogens. At Johns Hopkins University in Baltimore, Maryland, 69 percent of the rats injected with a chemical known to cause mammary cancer developed tumors vs. only 26 percent of the rats given the carcinogenic chemical plus sulforaphane.
In 1997, Johns Hopkins researchers discovered that broccoli seeds and three-day-old broccoli sprouts contain a compound converted to sulforaphane when the seed and sprout cells are crushed. Five grams of three-day-old broccoli sprouts contain as much sulforaphane as 150 grams of mature broccoli. The sulforaphane levels in other cruciferous vegetables have not yet been calculated.
Vision protection. In 2004, the Johns Hopkins researchers updated their findings on sulfora- phane to suggest that it may also protect cells in the eyes from damage due to ultraviolet light, thus reducing the risk of macular degeneration, the most common cause of age-related vision loss.
Lower risk of some birth defects. As many as two of every 1,000 babies born in the United States each year may have cleft palate or a neural tube (spinal cord) defect due to their moth- ers’ not having gotten adequate amounts of folate during pregnancy. The current R DA for folate is 180 mcg for a woman and 200 mcg for a man, but the FDA now recommends 400 mcg for a woman who is or may become pregnant. Taking a folate supplement before becom- ing pregnant and through the first two months of pregnancy reduces the risk of cleft palate; taking folate through the entire pregnancy reduces the risk of neural tube defects.
Possible lower risk of heart attack. In the spring of 1998, an analysis of data from the records for more than 80,000 women enrolled in the long-running Nurses’ Health Study at Harvard School of Public Health/Brigham and Women’s Hospital, in Boston, demonstrated that a diet providing more than 400 mcg folate and 3 mg vitamin B6 daily, either from food or supple- ments, might reduce a woman’s risk of heart attack by almost 50 percent. Although men were not included in the study, the results were assumed to apply to them as well.
However, data from a meta-analysis published in the Journal of the American Medical Association in December 2006 called this theory into question. Researchers at Tulane Univer- sity examined the results of 12 controlled studies in which 16,958 patients with preexisting cardiovascular disease were given either folic acid supplements or placebos (“look-alike” pills
with no folic acid) for at least six months. The scientists, who found no reduction in the risk of further heart disease or overall death rates among those taking folic acid, concluded that further studies will be required to verif y whether taking folic acid supplements reduces the risk of cardiovascular disease.
Adverse Effects Associated with This Food
Enlarged thyroid gland (goiter). Cruciferous vegetables, including cabbage, contain goitrin, thiocyanate, and isothiocyanate. These chemicals, known collectively as goitrogens, inhibit the formation of thyroid hormones and cause the thyroid to enlarge in an attempt to pro- duce more. Goitrogens are not hazardous for healthy people who eat moderate amounts of cruciferous vegetables, but they may pose problems for people who have a thyroid condition or are taking thyroid medication.
Intestinal gas. Bacteria that live naturally in the gut degrade the indigestible carbohydrates (food fiber) in cabbage, producing gas that some people find distressing.
Anticoagulants Cabbage contains vitamin K, the blood-clotting vitamin produced natu- rally by bacteria in the intestines. Consuming large quantities of this food may reduce the effectiveness of anticoagulants (blood thinners) such as warfarin (Coumadin). One cup of shredded common green cabbage contains 163 mcg vitamin K, nearly three times the R DA for a healthy adult; one cup of drained boiled common green cabbage contains 73 mcg vita- min K, slightly more than the R DA for a healthy adult.
Monoamine oxidase (MAO) inhibitors. Monoamine oxidase inhibitors are drugs used to treat depression. They inactivate naturally occurring enzymes in your body that metabolize tyra- mine, a substance found in many fermented or aged foods. Tyramine constricts blood vessels and increases blood pressure. If you eat a food such as sauerkraut which is high in tyramine while you are taking an M AO inhibitor, you cannot effectively eliminate the tyramine from your body. The result may be a hypertensive crisis.