That makes more sense for IBS (irritable bowel syndrome) than it does for IBD (inflammatory bowel disease). IBS is caused by the gut-brain nervous system acting up due to stress, and vagal maneuvers forcibly turn off the fight-or-flight response from the nervous system. On the other hand, IBD is caused by your immune system attacking itself in the gut, and the T cells aren't really connected to the nervous system in any physiologically relevant way. So your friends were probably talking about IBS, not IBD.