We have always fed yogurt, the live cultures in the yogurt help control the bad bacteria. Also, builds their immune system. Just make sure you get the yogurt with NO ASPERTAME and the regular low fat, not the "NO FAT". Once the fatty products are removed from the yogurt it defeats the entire purpose of feeding the yogurt.
We even put a little milk in scrambled eggs, I'm not sure how the myth about lactose intolerance in gliders started, but it seems to have been put out several years back and those who have not done their research are still preaching it. Mainly Pet Stores.
Just remember that everything that you do feed, feed in moderation.