Harvard Health Letter

By the way, doctor: Microwave cooking and nutrition

Q. Does cooking with a microwave take nutrients out of food?

A. A brief explanation of how microwave ovens work will help me set the stage for answering your question.

Microwave ovens cook food with waves of oscillating electromagnetic energy that are similar to radio waves but move back and forth at a much faster rate. These quicker waves are remarkably selective, primarily affecting molecules that are electrically asymmetrical — one end positively charged and the other negatively so. Chemists refer to that as a polarity. Water is a polar molecule, so when a microwave oven cooks or heats up food, it does so mainly by energizing — which is to say, heating up — water molecules, and the water energizes its molecular neighbors. The reason glass, masonry, and many types of plastic don't heat up in a microwave oven is that they're made up of nonpolar molecules.

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