Nutrition loss from over cooking?

ovi212

I was just wondering if anyone had any knowledge or facts on whether foods lose their nutrition if you over cook them? Which nutrients and how long is too long?

Right now my 2 main foods I've been eating that could be over cooked are turnip and zucchini. I boil the turnip cubes for about 40 min? And the zucchini I slice and cook at 425 in a toaster oven for ~30min and then on broil for ~15. It turns out pretty dry like hips (intention) but also a little black sometimes (but hey I like it that way, I burn my popcorn too lol). But is this bad?
I also cook 1/2c egg whites in the microwave for 1min45. Alright?

Are there any foods I should be more careful about overcooking? Generally I'm always afraid of under cooking...

Kanuenue

Vitamins can be denatured by heat. This website has a table showing which vitamins can be lost under what conditions.

http://www.beyondveg.com/tu-j-l/raw-cooked/raw-cooked-2e.shtml