Chewing gum. Bad or Good? It depends. If the gum has sugar in it, it can promote cavities because the bacteria that erodes enamel thrives in sugar. On the other hand, sugarless gum has been found to keep teeth cleaner if you don't have time to brush. It stimulates your saliva which keeps bacteria from growing.
And do microwaves kill all the nutrients in your food? The jury is still out on this. The only consensus is, that microwaves decrease the vitamin B12 content of foods. But the real destroyer of nutrients is prolonged exposure to heat and the addition of water. So whether you use the microwave or the stove top, overcooking and adding water can sap your food of its vitamins and minerals.