Supplement Series: Vitamin D (Part 1 of 5)

Articles on vitamin D are often effusive of its role in bone and joint health, but this series is meant to highlight the benefits of this crucial vitamin beyond your skeleton. Over five expert-informed articles, we’ll be discussing the role of cholecalciferol.

• Part 1. Gut

• Part 2. Cardiovascular

• Part 3. Cognitive

• Part 4. Metabolic

• Part 5. Immune

From inflammatory bowel disease to celiac disease, vitamin D plays an important role in keeping your gut healthy and happy.

Digest, Absorb and Process

The gastrointestinal system plays a large role in the process of food digestion and nutrient absorption. The human digestive tract, composed of organs such as the esophagus, stomach, small intestine, and large intestine, transports food and dissolved nutrients, breaking down complex molecules into simpler forms that can be absorbed from the GI tract into the bloodstream.

During the first stages of digestion, enzymes secreted from glands within the mouth and stomach break down complex foods into simpler components. As food leaves the stomach, it enters the small intestine for further digestion and absorption. Herein lies the majority of nutrient absorption as compounds like vitamin D are pulled through villi and transferred across capillaries to eventually enter circulation within the bloodstream. While also playing an important role in assisting these processes, the large intestine removes water-soluble substances before finally eliminating waste via defecation. The fantastic collaboration between this major bodily system is key to proper digestion within humans. 

How Does Vitamin D Influence Digestion?

Vitamin D receptors (VDR) are found in the cells lining the gut and researchers have explored its critical role in mucosal inflammation[1] and supporting the microbiome.[2] When researchers deleted a gene regulating VDR in the gut, it decreased a protein known as Claudin-15. This protein plays a major role in keeping the cells lining the gut close together, something known as the tight junction.[3] Gaps in the tight junctions are akin to holes in walls which make it easy for nutrients to slip out and pathogens to sneak in.

Butyrate, a short-chain fatty acid produced by bacteria in the gut, activates these receptors.[4] By consuming foods that promote butyrate production like legumes, fibre, vegetables and seeds, you support appropriate vitamin D processing.

Battistini, Carolina, et al. "Vitamin D modulates intestinal microbiota in inflammatory bowel diseases." International Journal of Molecular Sciences 22.1 (2020): 362.

Connection to Gastrointestinal Conditions

Vitamin D has been shown to play a role in the prevention and complementary treatment of several gastrointestinal disorders, including inflammatory bowel disease (Crohn's disease and ulcerative colitis), irritable bowel syndrome, and celiac disease.

Inflammatory bowel disease is a chronic inflammation of the gastrointestinal tract. Crohn's disease can affect any part of the GI tract, while ulcerative colitis is limited to the large intestine (colon). Symptoms of IBD include abdominal pain, diarrhea, weight loss, rectal bleeding, and fatigue. IBD is believed to be caused by a combination of genetic, lifestyle and environmental factors.

Vitamin D deficiency has been linked to an increased risk of Crohn's disease and ulcerative colitis.[5,6] Studies have shown that people with IBD who are deficient in vitamin D are more likely to experience flares than those who have sufficient levels of vitamin D.[7] Vitamin D supplementation has been shown to reduce the risk of flares and improve quality of life in people with IBD with researchers in one study concluding:

“Vitamin D levels were found to be independent predictors of ulcerative colitis disease activity scores and health-related quality of life scores.”[8]

Irritable bowel syndrome (IBS) is a disorder characterized by abdominal pain, bloating, constipation, and diarrhea. IBS is thought to be caused by a disturbance in the interaction between the brain and the gut. Research suggests that vitamin D may play a role in the development of IBS. A 2018 study found that people with IBS were more likely to be vitamin D deficient than those without IBS.9 The same study found that supplementation with vitamin D improved IBS symptoms. However, the research on this correlation is still young and higher quality trials are needed before any conclusions can be drawn.

Celiac disease is an autoimmune disorder characterized by an intolerance to gluten. When people with celiac eat gluten-containing foods, their immune system reacts by damaging the small intestine. This can lead to malabsorption of nutrients, gastrointestinal distress, and other health problems. One of the major nutrient deficiencies is in fact, vitamin D. Putting patients onto a gluten-free diet reduced inflammation and allowed their bodies to absorb more of the vitamin. Bone mineral density scans done 6 months after starting the diet showed significant improvements.[10]

In this first installment of our five-part series on vitamin D and health, we explored some of the ways in which this important nutrient affects disorders of the gastrointestinal tract, including inflammatory bowel disease, irritable bowel syndrome, and celiac disease.

Stay tuned for next week's post where we'll discuss how to keep your heart healthy with this important vitamin.!

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References

1. Li, Yan Chun, Yunzi Chen, and Jie Du. "Critical roles of intestinal epithelial vitamin D receptor signaling in controlling gut mucosal inflammation." The Journal of steroid biochemistry and molecular biology 148 (2015): 179-183.

2. Zhang, Yong-Guo, et al. "Vitamin D receptor protects against dysbiosis and tumorigenesis via the JAK/STAT pathway in intestine." Cellular and molecular gastroenterology and hepatology 10.4 (2020): 729-746.

3. Sun, Jun, and Yong-Guo Zhang. "Vitamin D Receptor Influences Intestinal Barriers in Health and Disease." Cells 11.7 (2022): 1129.

4. Chatterjee, Ishita, et al. "Vitamin D receptor promotes healthy microbial metabolites and microbiome." Scientific Reports 10.1 (2020): 1-18.

5. Eloranta, Jyrki J., et al. "Association of a common vitamin D-binding protein polymorphism with inflammatory bowel disease." Pharmacogenetics and genomics 21.9 (2011): 559-564.

6. Simmons, J. D., et al. "Vitamin D receptor gene polymorphism: association with Crohn's disease susceptibility." Gut 47.2 (2000): 211-214.

7. Gubatan, John, et al. "Low serum vitamin D during remission increases risk of clinical relapse in patients with ulcerative colitis." Clinical Gastroenterology and Hepatology 15.2 (2017): 240-246.

8. Dash, Kaibalya R., et al. "Association of Vitamin D Level With Disease Severity and Quality of Life in Newly Diagnosed Patients of Ulcerative Colitis: A Cross-Sectional Analysis." Cureus 13.7 (2021).

9. Williams, Claire E., Elizabeth A. Williams, and Bernard M. Corfe. "Vitamin D status in irritable bowel syndrome and the impact of supplementation on symptoms: what do we know and what do we need to know?." European journal of clinical nutrition 72.10 (2018): 1358-1363.

10. Verma, Anjali, et al. "Study of effect of gluten-free diet on vitamin D levels and bone mineral density in celiac disease patients." Journal of Family Medicine and Primary Care 11.2 (2022): 603.