Are proteins destroyed when heated?

As I recall from my biology classes, proteins are
denatured, not destroyed, through heating. When food's consistency is transformed
through cooking, for example -- meat and fish can became firmer or, if overcooked, even
plastic-like or rubbery -- denaturation is at work. (See the wikipedia link
below.)

Denatured protein is a current fitness fad. Because
it's a fad, I'm inclined to listen to the claims but also to be very skeptical. (See the
fitday.com link below.)

In general terms, cooking actually
makes it easier for enzymes to digest proteins, not harder, and denatures the proteins
in harmful bacteria to the point of destroying that bacteria's ability to survive. (See
the elmhurst.edu link.)