Broccoli is nutritious whether it’s steamed, roasted or tossed into a stir-fry. It contains vitamins A, C and K, minerals including calcium and potassium, fiber, and glucoraphanin, a compound that has been studied for possible health benefits. But how you cook it can affect some of those nutrients.
Boiling may cause water-soluble nutrients to seep into the cooking water. Cooking broccoli for a long time, or at high heat, can also reduce some of its beneficial compounds.
Registered dietitian Sol Figueroa says boiling tends to cause the greatest nutrient loss, particularly for vitamin C and glucoraphanin. If you do boil broccoli, using less water may help. You can also add the cooking water to soup or stew rather than pouring it away.
Glucoraphanin can be converted during digestion into sulforaphane, a compound being studied for potential antioxidant and anti-inflammatory effects. Researchers are also exploring possible links to liver, metabolic and gut health, as well as cancer prevention. Much of the research so far has involved laboratory or animal studies, Figueroa cautioned, so it’s too early to say broccoli prevents disease.
A little preparation may help preserve sulforaphane. Figueroa recommends chopping the broccoli and letting it rest for about 30 to 40 minutes before cooking. A sprinkle of mustard powder after cooking may help, too: mustard contains an enzyme that supports the conversion of glucoraphanin into sulforaphane, and that enzyme can be damaged by heat.
Steaming is another good option. It can help preserve broccoli’s enzymes, and some research suggests broccoli may retain vitamin C better during steaming than other vegetables do. Brief microwaving may also preserve nutrients.
Felice Kaufman, a food blogger and former chef, usually steams broccoli. She cuts the florets to roughly the same size and starts checking them after about three minutes. Her advice is simple: taste a piece, and take the broccoli off the heat once it’s tender enough to eat. It will continue cooking a little after you remove it.
Kaufman also cooks the stalk, trimming and slicing it before adding it with the florets. She prefers steaming, though she admits that when the sink is full, she sometimes just drops the broccoli into boiling water. It happens.
Ultimately, the best method may be the one that gets broccoli onto your plate. If your family prefers it roasted, that’s still a reasonable choice. As Kaufman puts it, a serving of broccoli—fresh, frozen, organic or conventional—is a better pick than processed food.
