A randomized controlled trial (RCT) published by the journal BMJ Open Gastroenterology found that patients with irritable bowel syndrome who supplement with vitamin D may experience an improved quality of life.
Irritable bowel syndrome (IBS) is a relapsing condition characterized by chronic abdominal pain or discomfort, bloating and spells of diarrhea or constipation. This is a common disorder, affecting at least 3 million individuals in the United States annually.
Although the etiology is unknown, individuals are more likely to develop IBS as a result of infection, dietary habits or a stressful life event. Researchers theorize that those who experience IBS likely have an altered gut flora. This overpopulation of pathogenic bacteria in the intestine may ultimately lead to inflammation and disturbed bowel function.
Past research suggests vitamin D helps regulate the immune system by reducing the levels of inflammatory proteins when they are overproduced. Vitamin D receptors are also found in the gut, leading researchers to theorize that vitamin D may act locally to normalize intestinal function, prevent pathogenic bacterial invasion and maintain cell integrity.
In the current study, researchers from the University of Sheffield hypothesized that vitamin D supplementation may provide a potential treatment effect for IBS patients. Therefore, they conducted a randomized, double blind placebo controlled pilot trial where patients were started on treatment in the springs and finished the trial in the summer.
A total of 51 IBS patients were randomly assigned to one of three treatment groups: vitamin D (3,000 IU a day as a sublingual spray) and probiotic, vitamin D and a single placebo or two placebo pills. At baseline, the patients had their serum 25(OH)D measured ( around 15 ng/ml for all three groups), completed a food frequency questionnaire (FFQ) and filled out a questionnaire describing their IBS symptoms. After two weeks, the patients were assigned a 12-week supply of supplements and completed biweekly IBS symptom questionnaires. At the final visit, participants had their vitamin D status measured and completed the questionnaires about IBS again.
Here is what the researchers found:
- Low vitamin D status was highly prevalent in IBS patients, with an average 25(OH)D status of 15.3±7.9 ng/mL (38.3 nmol/l).
- The two vitamin D groups increased to 37 ng/ml while placebo increased to 25 ng/ml, probably due to sun exposure.
- All three groups had significant improvements in IBS scales, including the placebo group.
- 8% of IBS patients who experience constipation, 70% who experience diarrhea and 81.6% who switch between bouts of diarrhea and constipation were vitamin D deficient.
- Serum vitamin D status showed a significant positive association with quality of life in IBS patients (p = 0.034).
The researchers concluded,
“The IBS population exhibits significant levels of vitamin D insufficiency and would benefit from screening and possible supplementation. The impact of IBS on quality of life may be reduced by vitamin D level.”
Due to the small sample size of this study, it would take a very large effect to provide statistically significant results. Also, the 10 ng/ml increase in 25(OH)D in the placebo group probably masked any benefits of supplementation. Therefore, the researchers call for a larger scaled trial with a longer duration in order to detect if a significant improvement in symptom severity scores may result from vitamin D supplementation.
Sturges, M. and Cannell, JJ. Closer look: low vitamin D status linked with irritable bowel syndrome. The Vitamin D Council Blog & Newsletter, January, 2016.