Save the vitamins in my vegtables!

Yes, heating food to a certain point (above 110 degrees fahrenheit, I believe) begins to "kill" the food.  Sometimes it can be detrimental to your health as well, because the heat destroys certain enzymes that may be in the food which your body needs to break it down.  If your body doesn't have the enzymes on hand, it will take nutrients FROM your cells to create the needed enzymes. 

Alternatively, your body just won't be able to break the cooked food down as easily and "undigested" food will enter the large intestines.  Yes, it'll eventually break down of course, but what happens then is that you can acquire allergies to the undigested foods over time.  (This same concept happens more often when you eat sugary foods)

It is true that "living food" is definitely the way to go to maximize nutrition. As man was evolving and living in the distant past, our digestive system was established to be that of mostly gathering and grazing on foods, and rarely if ever cooking it. That is why our bodies run most efficiently when eating many small meals throughout the day. One thing that you do need to make sure of is that all foods that will be eaten with minimal heating are properly handled, washed and stored. In this day and age of chemicals, pesticides, and even common fertilizers, we need to make sure we are concientous of where we get our foods and what we do to them before we eat them. This is true even of organically grown foods, with much of the natural fertalizers coming from animal waste, which although a healthy growth medium, but dangerous to us if taken in directly. A raw or nearly raw diet is very healthy, as long as it is done safely.