. . . if you want to get the most cancer-fighting nutrition out of your carrots, zucchini and broccoli. Despite the conventional culinary wisdom that raw is best in terms of preserving veggies’ nutritional value, scientists in Italy—where they know a little about food—find that the right kind of cooking actually preserves or even boosts their nutritional value, the researchers will report December 26 in the Journal of Agricultural and Food Chemistry.
In the new study, the researchers at the University of Parma measured how boiling, steaming, and frying affected the nutritional contents of carrots, zucchini and broccoli, especially such anti-cancer compounds as antioxidants and polyphenols. For those of you planning to serve any or all of these three during the holiday season, here’s the bottom line:
For carrots, boiling increased the total concentration of carotenoids 14 percent; frying reduced their concentration 13 percent and steaming reduced it just a little less. Levels of beta-carotene were not affected by boiling, though steaming caused levels to fall 10 percent and frying reduced them 24 percent. (Fried carrots? Oh, those Italians.) All three cooking methods significantly increased carrots’ total antioxidant concentration, good news for those eating these roots for their anti-cancer properties. Frying actually increased total antioxidant levels the most, followed by boiling and steaming. And the winner is: boiling, by a nose, since with carrots you can’t go wrong with any cooking method.
For zucchini, boiling did not affect the total concentration of carotenoids, though steaming and frying reduced it 22 percent and 35 percent, respectively. For the carotenoid beta-carotene, boiling and steaming actually increased it. Fried zucchini lovers, rejoice: frying raised the total concentration of antioxidants the most, as it did for carrots, though boiling and steaming also increased them. Frying wins out here because it induces the so-called Maillard reaction, whose products having antioxidant activities. The winner: frying, though it got a boost from the fact that it makes zucchini taste so much better than boiling and steaming do that you’ll eat more of the stuff. Just pick a heart-healthy oil, such as olive.
For broccoli, cooking also helps release carotenoids from the plant’s cells by breaking their bonds to proteins, leading to higher concentrations. As a result, boiled and steamed broccoli had higher levels of carotenoids (32 percent more and 19 percent more, respectively) than raw broccoli. Steaming increased broccoli’s content of glucosinolates, plant compounds touted for their cancer-fighting abilities. And the winner is: steaming.
I don’t know about you, but I’ve eaten my last raw zucchini hunk, my last uncooked broccoli floret and my final boring old carrot stick.