The Sensitive Gut

Understanding IBS

Open up your bowels and let the sun shine in; the myths about Vitamin D and IBS

vitd1It’s a no brainer.  Most people with IBS have low levels of Vitamin D, so the answer seems simple: if you can’t get enough sunshine in your life, take Vitamin D supplements. Some people with IBS certainly claim to feel better taking Vitamin D, but that may be because this powerful steroid suppresses inflammation.

Call me an old cynic, but like the majority of medical research, it ain’t necessarily so!  Life is rarely that simple, so before you dash down to Holland and Barrett to get your sunshine pills, let me try to unpick some of the assumptions that underpin the notion that Vitamin D cures IBS.

Most people with IBS are deficient of Vitamin D.  

According to some internationally accepted levels, the majority of the population of industrialised nations are deficient of Vitamin D.  This includes many quite healthy people with no signs of vitamin D deficiency.  This has prompted some countries to call for vitamin D supplements to be given to everybody. The notion that this ‘deficiency’ is related to low dietary intake or impaired photosynthesis because of lack of exposure to sunlight has been shown not to be true.  The most recent information suggests that people get adequate exposure to sunlight even in England and many foods are supplemented with vitamin D.

There is considerable controversy as to what constitutes a low level of Vitamin D.  This is because clinical scientists measure the ‘inactive’ 25 hydroxy Vitamin D (25(OH)D), which needs to be activated, normally in the kidney, to 1,25 hydroxy Vitamin D (1,25(OH)D).  A low level of 25(OH)D in people with chronic inflammatory illness may reflect more conversion to the active form and does not necessarily correlate with clinical evidence of Vitamin D deficiency.

Low Vitamin D may cause IBS

Vitamin D is said to be low in many chronic inflammatory conditions, including IBS, which can demonstrate a chronic low grade inflammation of the gut epithelium, probably related to a leaky gut and translocation of colonic bacteria.  Such infection sequesters more 25(OH)D, which in the presence of chronic infection is activated in a variety of tissues throughout.  Thus in chronically ill people, low 25(OH)D is often associated with increased active 1,25(OH)D, which stimulates the innate immune system to combat the ‘infection’.  So it could be that in common with other chronic inflammatory conditions, active Vitamin D levels are not low in IBS, they are actually increased.

Supplementation with Vitamin D reduces inflammation and IBS

There is very little evidence that is true.  A recent trial from Sheffield showed no significant effect of supplementation in IBS.  Vitamin D supplementation for other chronic inflammatory conditions have shown similarly inconsistent results.

Vitamin D supplementation is safe in recommended doses. 

Low grade infection might mean that vitamin D activation  is already very high. Giving supplements might therefore push it up to toxic levels.  Overdosing of Vitamin D can trigger extra absorption of calcium, and cause kidney stones, abdominal pain, mood disorders and muscle pain. High levels of vitamin D can also increase risks for strokes and heart attacks.


Confused?  Well, so am I.  All that we can conclude is that it seems far too early and may be even a little risky to recommend taking Vitamin D supplements for IBS.


Brazier, Yvette. “Low vitamin D levels associated with IBS.” Medical News Today. 21 December 2015.

Khayyat, Yasir, and Suzan Attar. “Vitamin D deficiency in patients with irritable bowel syndrome: Does it exist?” Oman Medical Journal 30, no. 2 (2015): 115-118.

Mangin M, Sinha, R and Fincher K.  Inflammation and vitamin D: the infection connection.  Inflamm Res. 2014; 63(10): 803–819.

Sprake, E., F., V.,A. Grant, and B., M. Corfe. “Vitamin D3 as a novel treatment for irritable bowel syndrome: single case leads to critical analysis of patient-centred data.” BMJ Case Rep., Dec 2012.


Thanks to Dr Felix, online doctor and pharmacy for sending in the idea for this post





One comment on “Open up your bowels and let the sun shine in; the myths about Vitamin D and IBS

  1. Joan Ransley
    April 7, 2016

    Really interesting Nick . I have posted a link to this on the ‘Useful article’ page of

    Liked by 1 person

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This entry was posted on April 6, 2016 by in Diet, Supplements, Uncategorized and tagged , , , .

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