Examine publishes rigorous, unbiased analysis of the latest and most important nutrition and supplementation studies each month, available to all Examine Members. Click here to learn more or log in.

In this article

Vitamin D(efense) against Crohn’s disease?

Immune benefits are often listed among the multitude of possible vitamin D effects. Most of the time, this is simplified to “defense against colds and flu”. But many conditions have an immune component — this particular study examines potential mechanisms by which vitamin D may help Crohn’s disease.

Study under review: Effects of Vitamin D Supplementation on Intestinal Permeability, Cathelicidin and Disease Markers in Crohn’s Disease: Results from a Randomised Double-Blind PlaceboControlled Study


There has been a big push in recent years for more digestive research, and this has resulted in many studies on topics like the intestinal microbiome, wheat and celiac disease, and irritable bowel syndrome. One severe digestive issue Study Deep Dives haven’t covered yet is Crohn’s disease (CD). While CD and the previously mentioned disease states are distinct from each other, there are quite a few similarities at the cellular and symptom level, so you may see some of the terms you are already familiar with from previous Study Deep Dives.

CD is an inflammatory bowel disease in the same family as ulcerative colitis. It may affect any region of the digestive tract, which spans from the mouth to the anus. However, CD primarily affects the large intestine, small intestine, or both. This can make it hard to diagnose Crohn’s, since the diagnosis largely depends upon observing an inflamed patch in a region of the digestive tract and CD may affect only a small fraction of it. Furthermore, if the inflamed region is in the small intestine, traditional colonoscopy techniques may not be able to reach the affected tissue. Patient symptoms, however, which include loose stool, fever, anemia, and abdominal pain, may be evaluated to aid a proper diagnosis. Currently there is no cure for this chronic disease. Patients may suffer relapses, exhibit a slightly reduced life expectancy, and experience significantly reduced quality of life.

The specific cause of CD is unknown, and it’s theorized to be influenced by several different factors. Some key players that have been identified are shown in Figure 1, and include genetics, the innate immune system of the gut, and the environment. At the genetic level, no single mutation appears to be causative of CD, though many may contribute to its development. Thus, having family members with CD increases one’s own risk of CD. Some of the biggest environmental players known to increase risk of development of CD include smoking and oral contraceptives (birth control)[1].

Figure 1: Possible pathway to the development of Crohn’s disease

While both environmental and genetic factors contribute to the risk of developing CD, the interaction between the gut microbiome and immune system is believed to cause the majority of symptoms that individuals experience. However, since high-risk individuals don’t always develop CD, and CD is not observed starting immediately at birth, it is believed that CD develops in a series of steps.These steps begin with a trigger event that leads to increased permeability of the intestines, which allows for increased uptake of secreted bacterial products. This can result in an overly aggressive immune response, leading to excess inflammation and destruction of healthy tissue, which can further increase intestinal permeability, resulting in a vicious cycle that can be difficult to interrupt. This complex interaction between immune system and host bacteria has inspired several therapeutic approaches, such as antibiotics[2] and immune response modulators[3].

Observational studies reveal several associations between vitamin D and CD. For instance, latitude[4] appears to be connected with the incidence of CD, and people that move from more equatorial to more polar regions also exhibit this trend[5]. Individuals living closer to the equator experience more intense sunlight and UV radiation, which results in the generation of vitamin D on our skin. And it turns out that people with CD have a high occurrence of vitamin D deficiency, despite supplementation[6]. In some investigations, vitamin D supplementation was found to reduce intestinal permeability and increase healing following injury[7] while also reducing inflammation[8]. These observations have led others to examine the effects of vitamin D supplementation on CD (with some of their results shown in Figure 2).

Figure 2: Clinical trials of the effects of vitamin D on Crohn’s

The current study took the exploration a step further, and examined how exactly vitamin D may be helping people with CD by measuring intestinal permeability, immune function, and several disease activity markers.

Crohn’s disease is a disease of the digestive tract characterized by patches of excess inflammation and increased intestinal permeability. People with Crohn’s disease often have vitamin D deficiency. Vitamin D plays a role in maintaining proper intestinal permeability and immune function. The objective of this study was to examine if vitamin D supplementation could be therapeutic for people with Crohn’s disease, and to measure changes in intestinal permeability and immune function as a possible mechanism of vitamin D action.

Who and what was studied?

Become an Examine Member to read the full article.

Becoming an Examine Member will keep you on the cutting edge of health research with access to in-depth analyses such as this article.

You also unlock a big picture view of 400+ supplements and 600+ health topics, as well as actionable study summaries delivered to you every month across 25 health categories.

Stop wasting time and energy — we make it easy for you to stay on top of nutrition research.

Try free for two weeks

Already a member? Please login to read this article.

What were the findings?

Become an Examine Member to unlock this article.

Already a member? Please login to read this article.

What does the study really tell us?

Become an Examine Member to unlock this article.

Already a member? Please login to read this article.

The big picture

Become an Examine Member to unlock this article.

Already a member? Please login to read this article.

Frequently asked questions

Become an Examine Member to unlock this article.

Already a member? Please login to read this article.

What I should know?

Become an Examine Member to unlock this article.

Free 2-week trial »

Already a member? Please login to read this article.

Other Articles in Issue #11 (September 2015)

  • A shot to the gut
    Alcohol intake and gut impacts have been researched before, but we still aren’t sure what exactly goes on after people drink. This study looked at what happens with gut bacterial products when people have multiple drinks at one sitting ... aka “binge drinking”.
  • Tea time means only tea for optimal EGCG absorption
    Many people drink green tea for health, and some take green tea or EGCG supplements in an attempt to shed extra fat. While these topics have been researched at length, there hasn’t been as much research on timing. This study looks at EGCG absorption with and without food.
  • Can omega-3s prevent cognitive decline?
    One of the most important issues with aging is decreased cognitive ability and eventually dementia. Since the brain has such high omega-3 content, many people supplement for prevention of these issues. This large, multi-year study put that practice to the test.
  • The study that didn’t end the low-fat/low-carb diet “wars”
    A recent metabolic ward study set the low-carb world on fire, and produced many inaccurate media headlines disparaging low-carb diets. We cover the study and its implications, detail by detail.
  • Interview: Dylan Dahlquist, MSc(c)
  • When is breakfast the most important meal of the day?
    With an increasing amount of research pointing to benefits of intermittent fasting, breakfast has been shunned by more and more people. But for those with type 2 diabetes, blood sugar is a central issue, and breakfast may play a major role in regulating it.
  • What to Expect When We’re Expecting: Fetal Programming and the Development of Taste Preferences
    By Margaret Leitch, Ph.D.
  • Gluten-intolerant? There’s a pill for that
    Some people are lactose intolerant, but still drink milk thanks to the availability of lactase enzymes. That setup isn’t yet possible for those who don’t handle gluten well. This study examines the efficacy of a promising enzymatic adjunct to a gluten-free diet.
  • Green tea: a potential pain in the neck
    Though it may not be as effective for fat loss as early studies suggested, green tea is still seen as extremely healthy. But animal evidence has pointed to possible thyroid side effects from excessive green tea consumption. How convincing is this evidence?