There is still a lot of mystery about what are the causes of Irritable Bowel Syndrome (IBS). However, there is more evidence that there is a dietary link, at least in some cases. Celiac sufferers will find that connection believable because of the way their disease symptoms tend to lessen on low-gluten diets. But, why does diet have such a large impact for diseases like IBS that are chronic and embarrassing? The key may be in understanding the role small intestinal bacterial overgrowth (SIBO) plays in a variety of related illnesses that can end up contributing to the appearance of IBS.