5.1 and 7.1 Information In Two Channels?

Is all of the information on a 5 or 7 discreet channel dvd condensed to two channels if the disc is played in stereo? Even though there will be no surround or rear channels, does that information just become split to right and left channels? Is any of the information on the soundtrack lost by playing it in only two channels?

In other words, if you play a 5 channel dvd on a system with three pairs of speakers in stereo to all six speakers, will any information be lost? Forget about the subwoofer channel, that's not important in this instance.
If you are only playing in two channel and--important point--you have all other speakers specified to NONE then toes the receiver or pre-pro will downmix to 2.0. Some bluray players like the Oppo allow you to specify a 2.0 downmix in te player. If you are using the analog stereo outs of the player then generally that will be a downmix.
So the answer is you don't loose the information. It will get mixed to the two channels.
It depends on the player and/or processor and how you have them set up. Certainly most of them CAN downmix to 2 or 3 channels. You need to find out how that is done in your particular equipment.