Broccoli is a member of the cabbage family, along with cauliflower, kale, Brussels sprouts and other cruciferous vegetables. Like many of its botanical cousins, broccoli packs crunch and a nutritious punch as an excellent source of fiber, vitamin C, lutein and beta-carotene. Broccoli is served raw in salads or alongside other vegetables and dipping sauce in crudités and hors d'oeuvre platters. Of course, broccoli is also served as a cooked vegetable. While there is no “right” way to cook broccoli, certain cooking methods better preserve the vegetable’s nutrient content.
Some people boil vegetables, including broccoli. However, Professor Paul Thornalley of the University of Warwick in the UK says that boiling broccoli diminishes its antioxidant value. Specifically, boiling reduces compounds known as glucosinolates, which are converted in the body into anti-cancer agents called isothiocyanates. Thornalley and his colleague, Dr. Lijiang Song, found that cooking broccoli in boiling water reduced the glucosinolate content by 20 to 30 percent after five minutes, up to 50 percent after 10 minutes and 77 percent after 30 minutes. While most people aren’t inclined to boil broccoli for as long as 30 minutes, clearly boiling may not be the best way to cook this vegetable.
If you like Chinese cuisine, stir-frying is a great way to cook and enjoy broccoli. Paired with other vegetables that lend themselves to this method of cooking, such as water chestnuts, sliced carrots and bean sprouts, broccoli adds contrast in terms of color, taste and texture. The key here is to refrain from overcooking the food. Stir-frying is a quick method of cooking vegetables in hot oil just to the point that they render their flavorful sugars but remain crisp. As far as nutrient preservation, Thornalley and Song found no significant loss of glucosinolate content when broccoli is stir-fried for five minutes or less.
Steaming is a popular way to cook broccoli because it’s fast and retains the vegetable's color and texture. According to a study published in the Nov. 23, 2006, issue of the “Journal of Food Additives and Contaminants,” steaming broccoli may also increase its nutritional value. The researchers found that steam-cooking broccoli increased levels of glucosinolates and other antioxidant compounds, as well as beta-carotene, lutein and alpha- and gamma-tocopherols. There was no effect on vitamin C content.
This is probably the easiest way to cook broccoli because the cooking vessel can double as a serving dish, so there’s less to clean up. Color and texture retention is also satisfactory, as long as you don’t “nuke” the vegetable too long. According to Thornalley and Song, microwaving broccoli for three minutes or less does not result in a significant loss of glucosinolates.
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- USDA: National Nutrient Database for Standard Reference, Release 23, 2010
- University of Warwick: Research Says Boiling Broccoli Ruins Its Anti-Cancer Properties
- “Journal of Food Additives and Contaminants”; Changes in the Content of Health-Promoting Compounds and Antioxidant Activity of Broccoli After Domestic Processing; Gliszczynska-Swiglo A, et al.; 2006
Karyn Maier is a seasoned columnist and feature writer. Since 1992, her work has appeared in Mother Earth News, The Herb Quarterly, Better Nutrition and in many other print and digital publications. She is also the author of five books, and is published in six languages.