1. Acetic acid (main component of vinegar) is a key nutrient in the Krebs Cycle (how each cell in your body makes energy). It is thought that a large part of the body's acetic acid need is met by the bifido-bacteria in the colon. So if you have any kind of intestinal complaint supplementing with vinegar may be crucial.
2. Acetic acid is essential for good intestinal health. Amongst other things it inhibits viral replication, although the exact mechanism is not yet known. Vinegar has been used successfully in HIV patients to keep viral load down. (see Mark Konlee's books and website (www.keephope.net).