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The microwave has gotten a bit of a bad rap about its effects on nutrients. Cooking and heating food by any method can result in some degradation of nutrients. Vitamins C and B12, for instance, degrade quickly when a food is heated. But other nutrients may actually benefit from the rise in temperature. For example, carotenoids, the antioxidants found in colorful vegetables like carrots and tomatoes, increase when the proteins that bind them break down during heating, said Guy Crosby, the science editor for America’s Test Kitchen and an adjunct associate professor at the Harvard T.H. Chan School of Public Health.

The Harvard Health Letter recently concluded that microwaving may be preferable to other methods for heating food. “Because microwave cooking times are shorter, cooking with a microwave does a better job of preserving vitamin C and other nutrients that break down when heated,” it reported. “The cooking method that best retains nutrients is one that cooks quickly, heats food for the shortest amount of time, and uses as little liquid as possible. Microwaving meets those criteria. Using the microwave with a small amount of water essentially steams food from the inside out. That keeps more vitamins and minerals than almost any other cooking method.”

However, Ashim Datta, a professor of food engineering at Cornell University, cautioned that because microwaves heat food unevenly, nutrients are more likely to be broken down in spots that get extremely hot. In some cases, Dr. Datta said, microwaving could lead to more degradation over all than another warming method.

To help avoid these problems, put a lid on food in the microwave to retain moisture, and keep the power relatively low to ensure that food is cooked rapidly, but not overheated, said Rebecca Solomon, director of clinical nutrition at Mount Sinai Beth Israel hospital in New York City.

But for people who eat a balanced diet, microwave heating is unlikely to have a meaningful effect, positive or negative, on nutritional intake.