Study finds vitamin D improves irritable bowel syndrome

Sufferers of irritable bowel syndrome (IBS) put up with abdominal discomfort, diarrhoea and constipation. But what role (if any) does vitamin D play in this chronic condition?

vitamin d deficiency

Vitamin D research

Due to it’s effect on the immune system and inflammation, researchers have began studying vitamin D’s effect on IBS. A case study reported that IBS symptoms significantly improved in a patient taking 3000 IU of vitamin D daily. Researchers have since completed a randomised controlled trial to evaluate the effects of vitamin D on IBS further.

A total of 74 men and women between the ages of 18 and 70 years were recruited from the outpatient clinic at Jundishapur University of Medical Sciences, Ahvaz, Iran. The patients were randomly selected to receive either 50,000 IU of vitamin D3 or placebo every two weeks for a period of six months. They used a quality of life questionnaire to record the effects the vitamin D supplementation and the placebo had on the patients’ lives.


The Results

After the six months the researchers found that the vitamin D group experienced significant improvements in the mean IBS Quality of Life scores in dysphoria, health worries, food avoidance, social reaction, relationships and sex life in comparison to the placebo group.

The researchers concluded,

“The findings indicated that vitamin D supplement therapy has beneficial effects on IBS-QoL and the IBS severity score correlating with improved abdominal pain and distention, flatulence, rumbling, and overall GI symptoms as compared to the placebo group.”

At the beginning of the trial the patients were vitamin D deficient and by the end they were not. However the placebo patients remained deficient.

vitamin d deficiency

Whilst the study was relatively strong, it is important to note that there were a couple of limitations. Firstly the vitamin D supplementation was administered once every two weeks, rather than on a daily basis.  And secondly, the sample size was quite small. However, there is no doubt it is a step in the right direction.

Vitamin D deficiency

It is widely reported that vitamin D deficiency is a global health problem. If you consider how our lifestyles over the past 40 years have changed, it does not take long to figure out that we spend a lot more times indoors then we ever used to. We recently wrote about Gwyneth Paltrow’s vitamin D deficiency and 7 signs you may be deficient. If you would like to read how you can increase your vitamin D levels, then please read our guide.


Abbasnezhad A, Amani R, Hajiani E & et al. Effect of vitamin D on gastrointestinal symptoms and health-related quality of life in irritable bowel syndrome patients: a randomized double-blind clinical. Neurogastroenterology & Motility, 2016.


*It is important to note that you should always consult your GP before taking any additional supplements.