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Steaming your vegetables may boost their nutritional value, a new Brazilian review finds.
Researchers analysed 21 studies that looked at how different cooking methods affected vegetables’ levels of antioxidants, compounds that may fend off cancer, cardiovascular disease, diabetes, osteoporosis and neurodegenerative disease.
Most cooking methods—baking, boiling, and microwaving—break down vegetables’ tissues, destroying some antioxidants. Boiling can leach even more antioxidants, because some of the disease-fighting compounds dissolve in hot water.
Every vegetable varies in how it reacts to each cooking method. But the analysis found that on average, boiling reduced vegetables’ levels of polyphenols—a type of antioxidant—by 38 percent. Steaming, however, increased polyphenol content by 52 percent.
Steaming tends to increase polyphenol levels because the heating process is gentler and the vegetables aren’t submerged in water, says Elizabeth H. Jeffrey, Ph.D., a professor of nutritional sciences at University of Illinois at Urbana-Champaign.
The gentle heat actually releases some polyphenols from bonds that would have prevented your body from being able to digest them if you had eaten the vegetables raw, Jeffrey says.
Of course, that doesn’t mean that microwaved or roasted broccoli is bad for you—it just might have fewer antioxidants than the steamed stuff.
No matter how you cook your produce, just don’t overdo it. Cooking vegetables for too long at high temperatures tends to destroy more antioxidants, the researchers say.
Remove them from heat when they’re tender-crisp. You should be able to pierce them with a fork—but they shouldn’t fall apart when you do so