A new study indicates the potential benefit of Vitamin D for IBS (or perhaps the IBS is causing decreased vitamin D levels, but the first hypothesis appears more likely):
"The data provide evidence for widespread vitamin D insufficiency in people with IBS. There may be benefit to testing IBS patients’ vitamin D status and providing supplementation. There is a positive association between vitamin D status and quality of life measures, supporting a potential interaction between vitamin D and mental health and well-being. Clinicians may consider trialling vitamin D with patients with IBS as part of a nutritional management strategy. The results suggest a larger, adequately powered trial may be justified."
The above quote is from the Abstract for the following study:
Vitamin D associates with improved quality of life in participants with irritable bowel syndrome: outcomes from a pilot trial http://bmjopengastro.bmj.com/doi/full/10.1136/bmjgast-2015-000052