The exact nutritional values of an ounce of steamed broccoli depend on how much cooking water is used, whether the broccoli touches the water and how long it spends in the steamer. Direct contact with boiling water appears to degrade levels of some of its potent disease-fighting nutrients. Choose raw or steamed over boiled broccoli to preserve as much of its nutritional content as possible.
Broccoli
Broccoli is a cruciferous vegetable known for its florets, or bud clusters. Its stalks and leaves are also edible. Originally grown in Italy, 90 percent of the broccoli in the United States is now harvested in California. It is widely available fresh and frozen in most areas. Choose dark-green broccoli with closed buds and stalks that are firm but not woody. Frozen broccoli may contain reduced amounts of calcium, iron, riboflavin and thiamin.
Raw Broccoli Nutrition
A 1-oz. serving of raw, chopped fresh broccoli contains only about four calories. Broccoli is high in a number of minerals. The same 1-oz. serving provides 5.4 mg of calcium, 2.4 mg of magnesium, 7.5 mg of phosphorous, 36 mg of potassium and 3.75 mg of sodium. It also offers 10 mg of vitamin C, 7 mcg of folate, 159 mcg of lutein and zeaxanthin, 41 mcg of beta-carotene and 71 IU of vitamin A, as well as smaller amounts of many of the B-complex vitamins.
Broccoli and Disease
The American Cancer Society reports that eating a diet rich in cruciferous vegetables such as broccoli may help prevent some types of cancer. This effect is attributed to lutein and antioxidant vitamins such as vitamin C, beta-carotene and folate. Raw broccoli also contains a cancer-fighting enzyme called sulforaphane and a compound called indole-3-carbinol, which may alter estrogen levels and help prevent the growth of breast and prostate cancers. More studies need to be conducted to determine which nutrients or what combination of nutrients is responsible for these benefits.
Cooking Broccoli and Nutrition
Elizabeth Jeffery, a professor of nutrition at the University of Illinois, recommends steaming broccoli for two to four minutes, instead of boiling or microwaving it, to preserve its cancer-fighting compounds. The U.S. Department of Agriculture has found that green vegetables lose 45 percent of their vitamin C when covered with water and boiled and 40 percent when cooked in a small amount of water. The boiling process has a similar effect on other water-soluble vitamins, such as vitamin A and folate. Registered dietitian Karen Collins of MSNBC.com's "Nutrition Notes" points out that steaming vegetables for a short time does not produce the same nutrient loss.
References
- American Cancer Society; Broccoli; 2008
- Centers for Disease Control and Prevention: Vegetable of the Month – Broccoli
- U.S. Department of Agriculture National Nutrient Database for Standard Reference: Broccoli, Raw
- MSNBC.com: Nutrition Notes: Avoid Watering Down Veggie Nutrition; Karen Collins; 2007
- “News-Gazette”; Broccoli Fights Cancer Best When it Gets a Little Steamed; Debra Pressey; February 2011
- United States Department of Agriculture, Agricultural Research Service; USDA Table of Nutrient Retention Factors, Release 6; 2007
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