Microwaves can vibrate Water molecules. It shakes the water in molecular level until it gets heated. This force can break many ionic bonds of molecules and disintegrate many vitamins. But the Microwave mostly works on water molecules. But almost the same thing happens when you cook on a gas cooker. But the Microwave is a radiation. The radiation can remain on the food for some times. If you take Microwaved food directly through mouth, you are eating some harmful radiations as well. So If you microwave some food, just let it radiate out harmful radiation for a while (few minutes) before eating. If you use Microwave it is not only harmful to food but also to your health. The risk is prevented to get advertised to maintain their profits by companies who make these stuff. But there is a tolerant level of radiation our body can handle. If it is below the risk level, then it is OK. Anyway the food we eat has some radiation naturally. If you Microwave your all three meals, then there will be a small risk.