Is a Vitamin D Deficiency Behind Your IBS?

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Vitamin D has been receiving a lot of research attention for two reasons: More information is being gained as to its role in our health and, in our overall population, rates of vitamin D deficiency are increasing. One small but emerging area of research has to do with vitamin D's relationship with irritable bowel syndrome (IBS). In this overview, you will become educated about vitamin D, find out what the latest research is uncovering regarding its role in IBS, and how to ensure you are taking in adequate amounts of this important substance.

The Importance of Vitamin D

Vitamin D is not your typical vitamin. Unlike other vitamins, your body can actually manufacture vitamin D when you are exposed to sunlight. You may see it described in some sources as a hormone, but it appears that the vitamin itself provides the basis for certain hormones to be manufactured within the body.

Vitamin D belongs to the class of fat-soluble vitamins, which means that the vitamin can be stored within your body. This is in contrast to water soluble vitamins which dissolve in water and are available to your body's tissues but are not stored. This distinction is important because the storage factor of a fat-soluble vitamin leaves you at risk for a buildup of the vitamin to toxic levels.

You can obtain vitamin D through sun exposure, it is found naturally in some foods, it has been added to many fortified foods, and it can be taken in supplement form.

Vitamin D is most important for its role in calcium absorption and in maintaining calcium and phosphate concentrations in your blood.

Vitamin D, therefore, plays an important role in bone health. Vitamin D is also thought to play a role in the health of our immune systems, the functioning of our muscles, and in reducing inflammation.

Vitamin D Deficiency

Due to the importance of vitamin D in so many of our body's systems, a deficiency can lead to adverse health problems.

This is why your doctor is likely to recommend that your vitamin D levels be assessed through blood work. Levels lower than 30 nmol/L are generally considered to be low, while levels above 50 nmol/L are generally considered to be adequate. Levels higher than 125 nmol/L may be associated with health problems.

If you are deficient in vitamin D it may be because you are not taking enough of the vitamin in through your diet, you don't get exposed to enough sunlight, or you have an impaired ability to absorb the vitamin. You are at greater risk for vitamin D deficiencies if:

  • You are an older adult.
  • You have dark skin.
  • You are very rarely exposed to sunlight.
  • You have a health condition that involves fat malabsorption, such as inflammatory bowel disease.
  • You are significantly overweight or have had gastric bypass surgery.
  • You are following a diet for a milk allergy, lactose intolerance, or you are following an ovo-vegetarian or vegan diet.

Vitamin D and IBS

As stated above, researchers have recently been looking into a possible connection between a vitamin D deficiency and IBS.

This interest was triggered by the fact that vitamin D deficiency has been associated with many chronic conditions. In addition, bone loss from vitamin D deficiency has been observed in several gastrointestinal disorders, including inflammatory bowel disease, celiac disease, and people who have had part of their stomach surgically removed. Of particular relevance to the question as to whether vitamin D plays a role in IBS are research findings that show that IBS patients are at higher risk for osteoporosis.

However, given all of the theoretical factors listed above, it was actually a single case study that seemed to get the ball rolling in terms of conducting actual studies to shine some light on a possible connection between vitamin D and IBS. According to the report, a 41-year-old woman who had experienced severe symptoms of IBS-D for over 25 years decided to try taking a high dose of a vitamin D supplement after getting the idea from social media. This intervention resulted in significant improvement of her symptoms, which return whenever she stops taking the supplement. Of course, we can draw no conclusions based on one person's experience, but this report appears to have prompted other researchers to conduct other types of studies on the subject.

Results of a case control study, which compared the levels of vitamin D between a group of 60 IBS patients and 100 control group individuals, indicated that IBS patients were significantly more likely to have a vitamin D deficiency. A deficiency was detected in 81 percent of the IBS patients compared to 31 percent of the control subjects.

A pilot study, one in which a very small group of individuals is used to test out a hypothesis, sought to compare a vitamin D supplement with either a placebo or a combination pill of a probiotic and vitamin D. Keeping in mind that a pilot study does not offer information about statistical significance, the results suggested that a large proportion of the IBS subjects tested as having a vitamin D deficiency. Supplementation increased vitamin D and improved quality of life scores but did not significantly improve IBS symptoms.

A somewhat larger study was conducted that compared a six-month trial of a vitamin D supplement with a placebo in a group of 90 IBS patients. The supplement or placebo was described as a "pearl" to be taken every two weeks. The results indicated that the vitamin D supplement was significantly more effective in easing IBS symptoms (including abdominal pain, distension, flatulence, and rumbling) and their severity, as well as quality of life than the placebo. The only symptom that was not improved by the vitamin D was "dissatisfaction with bowel habits."

At this point, further research is clearly needed to come to any conclusions about the relationship between vitamin D levels and IBS. We also need to keep in mind that although this early research points to a connection, we don't know what is causing what—is the IBS causing the vitamin D deficiency, is the vitamin D deficiency causing the IBS, or is there some other unknown factor contributing to both problems.

How to Ensure You Are Getting Enough Vitamin D

Although research on the relationship between IBS and vitamin D is far from conclusive, it is important that you make sure that your body has sufficient levels of vitamin D for reasons separate from your digestive problems. If you have not already done so, speak with your doctor to have your level checked. Once you have a sense of your level, you can speak with your doctor about what things you can do to ensure that your body is getting enough of this essential substance. Keep in mind that there are three main ways to take in vitamin D:

  • Food: There are not many foods that naturally contain vitamin D. Those that do include fatty fish (mackeral, salmon, tuna), cheese, egg yolks, some mushrooms and cow's liver. Many processed foods have had vitamin D added to them, most notably cows' milk. Other fortified foods include many brands of breakfast cereals, orange juice, and yogurt. 
  • Sun exposure: Exposure to the sun is certainly a way to take in more vitamin D, but clear guidelines for this are hard to find. Sun exposure has been linked to skin cancer. Therefore dermatologists typically recommend that sunscreen be used whenever one is out in the sun to minimize your risk of getting skin cancer. Other branches of medicine suggest that small amounts of sun exposure a couple of times a week may be enough to ensure adequate vitamin D levels within the body. The amount of vitamin D your body can convert for use is also going to depend on the strength of the sunlight, which varies depending not only on time of day, but also where you live. Your best bet is to discuss the issue with your doctor to decide on what the most prudent course would be for you in terms of getting sun exposure.
  • Vitamin D supplements: Taking a vitamin D supplement is an additional option for ensuring that your vitamin D levels are sufficient. Interestingly, due to the growing awareness of an overall increased risk of vitamin D deficiency in the overall population, researchers have increased the long-standing guidelines for dosing. The current recommended daily allowance (RDA) is 600 IU a day for individuals aged 4 to 70. The RDA is increased to 800 IU a day for individuals age 71 and older. However, the correct dosage for you should be decided based on a discussion with your doctor, based on your bloodwork, your age, your medical history, and your lifestyle.


Abbasnezhad A 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 trial. Neurogastroenterology & Motility. first published online: May 7, 2016.

Khayyat Y. & Attar S. Vitamin D Deficiency in Patients with Irritable Bowel Syndrome: Does it Exist? Oman Medical Journal. 2015; 30:115-118.

New Recommended Daily Amounts of Calcium and Vitamin D. NIH Medline Plus. Winter 2011.

Sprake E, Grant V. & Corfe B. Vitamin D3 as a novel treatment for irritable bowel syndrome: single case leads to critical analysis of patient-centred data. BMJ Case Reports. 2012; bcr-2012-007223.

Vitamin D: Fact Sheet for Health Professionals. National Institutes of Health. Accessed May 9, 2016.

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