Microwave heating works by heating the water in foods. The frequency used in microwave ovens optimally heats water molecules. The microwave energy is converted into heat energy of the water molecules, which in turn heat the other molecules in the food. That is why dry foods such as rice and pasta will not cook in a microwave unless they are in some water.
More interesting stuff from that site.
Hope that clears things a little
You do lose a fair bit of the vit B12 as it converted to an unsuable form for us :-)
