Vitamin D Supplementation in IBS

Inclusion Criteria: 1. Provide signed and dated informed consent and understand the nature of the study sufficiently to allow completion of all study assessments. 2. Be ambulatory, community dwelling, 18 to 80 years, inclusive 3. Meet Rome IV diagnostic criteria for IBS 4. Have IBS of at least "moderate" severity, i.e., have a score on the IBS-SSS of \> 175 (0-500) at the baseline visit (Visit 1) 5. If the patient is on medications which affect the gastrointestinal tract or visceral sensation (e.g., tricyclic antidepressants, fiber, antispasmodics, etc.) they must be on a stable dose for at least 1 month prior to entering the study and for the duration of the study. Exclusion Criteria: 1. Have a history of intractable IBS, defined as continuous, unremitting and severe abdominal pain. 2. Be pregnant or lactating. 3. Have an established diagnosis of any concomitant bowel disturbance that would interfere with the assessment of efficacy or safety in the study (e.g., Hirschsprung's disease, inflammatory bowel disease, celiac disease). 4. Report warning symptoms (i.e., rectal bleeding, weight loss \>10%, iron deficiency anemia, etc.) otherwise not explained 5. Have undergone previous abdominal surgery (with the exception of uncomplicated appendectomy, cholecystectomy, hysterectomy, or polypectomy \> 6 months prior to enrollment). 6. Have a history of metabolic or inflammatory disease that may affect bowel motility (e.g., inflammatory bowel disease, celiac, sarcoidosis, connective tissue disease, amyloidosis, or poorly controlled hypo/hyperthyroidism). 7. Have a history of significant concomitant psychiatric, neurological, metabolic, hepatic, renal, infectious, hematological, cardiovascular, gastrointestinal, or pulmonary illness. If there is a history of such disease but the condition has been stable for more than one year and is judged by the Investigator not to interfere with the patient's participation in the study, the patient may be included. Staff will document such cases. 8. Have a history of drug, excluding nicotine or caffeine, or alcohol abuse within 2 years of entry into the study 9. Exhibit abnormalities on physical examination, have abnormal vital signs, or clinical laboratory values, unless these abnormalities are judged to be clinically insignificant by the Investigator. Such cases will be noted. 10. Active laxative abuse. 11. Unable or unwilling to cooperate with the study protocol or considered by the Investigator to be unsuitable for the study. 12. Currently taking Vitamin D supplements 13. Diagnosis of osteoporosis 14. Currently bisphosphonate medications 15. Those who taking medication known to interfere with Vit D