Protection against certain cancers. Naturally occurring chemicals (indoles, isothiocyanates, glucosinolates, dithiolethiones, and phenols) in cabbage, Brussels sprouts, broccoli, cauliflower, 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 transformation 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 inactivate 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.

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 mothers' not having gotten adequate amounts of folate during pregnancy. The current RDA 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 becoming 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.

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 Woman's Hospital in Boston demonstrated that a diet providing more than 400 mcg folate and 3 mg vitamin B₆ a day from either food or supplements, more than twice the current RDA for each, may reduce a woman's risk of heart attack by almost 50 percent. Although men were not included in the analysis, the results are assumed to apply to them as well. NOTE: Fruit, green leafy vegetables, beans, whole grains, meat, fish, poultry, and shellfish are good sources of vitamin B6.

Adverse Effects Associated with Cabbage

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 produce 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.

Food/Drug Interactions

Anticoagulants. Like other leaf vegetables, cabbage contains vitamin K, the blood-clotting vitamin produced naturally by bacteria in our intestines. Additional intake of vitamin K may reduce the effectiveness of anticoagulants (warfarin, Coumadin, Panwarfin), so that larger doses may be required.

Monoamine oxidase (MAO) inhibitors. Monoamine oxidase (MAO) inhibitors are drugs used to treat depression. They inactivate naturally occurring enzymes in your body that metabolize tyramine, 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 MAO inhibitor, you cannot effectively eliminate the tyramine from your body. The result may be a hypertensive crisis.