Eat your broccoli regularly and you'll get significant amounts of folate and vitamins A, C and K, as well as a variety of phytochemicals linked to beneficial health effects, including a lower risk for cancer. However, broccoli is often cooked, potentially decreasing the amount of these nutrients depending on the cooking method and time. Overcooking your broccoli could reduce the potential health benefits of eating this nutritious vegetable.
Long cooking times and cooking with a lot of water cause losses in vitamin C. Some of the B vitamins, including thiamine and folate, are also heat sensitive and easily destroyed if you cook your broccoli for too long or at temperatures that are too high. The smaller you cut your broccoli, the more easily nutrients will be lost. Fat-soluble vitamins like A, D, E and K aren't as affected by cooking.
While broccoli isn't a great source of any minerals, it does provide some calcium, potassium, iron and phosphorus. Minerals generally aren't greatly affected by cooking time. However, an article published in November 2010 in "Consumer Reports" noted that boiling can leach out up to 15 percent of the minerals from your vegetables, so avoid this cooking method to help maintain the minerals in your broccoli.
Cooking affects different phytochemicals -- beneficial plant chemicals -- in different ways. While it decreases compounds called glucosinolates, it increases the amounts of lutein, beta-carotene and alpha- and gamma-tocopherol, according to a study published in "The International Journal of Food Sciences and Nutrition" in February 2013. Longer cooking times, such as those used when overcooking broccoli, increased these effects.
Best Cooking Methods
Steaming helps maintain some of the nutrients in broccoli, including vitamin C and chlorophyll, better than microwaving, boiling or stir-frying, according to a study published in "The Journal of Zhejiang University SCIENCE B" in August 2009 that compared the effects of cooking broccoli for 5 minutes using each of these cooking methods. If you stir-fry your broccoli, use extra virgin olive oil since this helps maintain both the glucosinolates and vitamin C in the broccoli, according to a study published in "The Journal of Food Science" in 2007. Other types of oil are less effective in maintaining these nutrients. When steaming or boiling broccoli, it needs very little water and only takes 3 or 4 minutes to cook -- anything more is overcooking and may cause nutrient losses.
- Journal of Zhejiang University SCIENCE B: Effects of Different Cooking Methods on Health-promoting Compounds of Broccoli
- International Journal of Food Sciences and Nutrition: Effects of Various Heating Methods on Glucosinolate, Carotenoid and Tocopherol Concentrations in Broccoli
- Journal of Agricultural and Food Chemistry: Effects of Microwave Cooking Conditions on Bioactive Compounds Present in Broccoli Inflorescences
- Journal of Food Science: Effects of Stir-Fry Cooking with Different Edible Oils on the Phytochemical Composition of Broccoli
- University of Kentucky Extension: Preserving Nutrients in Food
- American Council on Exercise: How Much Difference Is There in Nutritional Value Between Fresh and Frozen Fruits and Vegetables?
- Consumer Reports: Get More Out of Your Vegetables
- USDA Nutrient Data Laboratory: Broccoli, Raw
- University of Illinois Extension: Broccoli
Based in Massachusetts, Jessica Bruso has been writing since 2008. She holds a master of science degree in food policy and applied nutrition and a bachelor of arts degree in international relations, both from Tufts University.