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Vitamin D and Your Gut Health

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4 min read


Vitamin D plays a role in intestinal homeostasis by influencing the tight junction architecture, bacterial colonization, and anti-inflammatory responses.

Written by

Dr. Geethika. B

Medically reviewed by

Dr. C. Elanchezhian

Published At June 14, 2022
Reviewed AtMarch 6, 2023


Vitamin D is both a vitamin obtained through the diet and a hormone produced by our bodies. It is a fat-soluble vitamin that aids in the absorption and retention of calcium and phosphorus, both of which are essential for bone formation. Vitamin D has also been shown in laboratory studies to inhibit cancer cell development, aid infection control, and reduce inflammation. Vitamin D receptors can be found in a variety of organs and tissues throughout the body, suggesting that it has vital functions beyond bone maintenance.

Vitamin D is only found in a few foods naturally, but it is fortified in others. Because it is difficult to eat enough vitamin D from food, the best option for most individuals to acquire enough is to take a supplement. Vitamin D supplements come in two types: vitamin D2 (also known as ergocalciferol or pre-vitamin D) and vitamin D3 (sometimes known as cholecalciferol). Both are naturally occurring forms that are produced in the presence of ultraviolet-B (UVB) rays from the sun, earning it the nickname "the sunshine vitamin," but D2 is produced by plants and fungi, while D3 is produced by animals, including humans. Vitamin D is produced primarily in the skin, but many people have insufficient amounts because they live in areas where sunshine is limited in the winter or because they have little sun exposure due to spending most of their time indoors. Also, those with darker skin have lower vitamin D blood levels because the pigment melanin serves as a shade, limiting vitamin D production. This also reduces the damaging effects of sunlight on the skin and reduces the risk of skin cancer.

Although vitamin D is best known for its role in calcium homeostasis, it also has a number of direct and indirect immune-system regulatory effects, including promoting regulatory T cells (Tregs), inhibiting Th1 and Th17 cell differentiation, impairing B cell development and function, and lowering monocyte activation. Vitamin D may have medicinal potential due to its immunosuppressive properties. In reality, several preclinical investigations in MS (multiple sclerosis) and colitis models (though fewer in arthritis and lupus) have shown that oral or intraperitoneal vitamin D treatment is beneficial. However, clinical investigations have failed to show a clear advantage, implying that the relationship between vitamin D and autoimmunity is more complex than previously thought.

What Is the Gut Microbiome?

The human microbiome is defined as an ecological community of commensal, symbiotic, and pathogenic microbes that live on and in our bodies. It is made up of 12 different bacterial phyla, with Bacteroidetes, Proteobacteria, Firmicutes, Actinobacteria, and Euryarchaeota accounting for 93.5 percent of the total. Intestinal microorganisms aid in the breakdown of food into chemicals and nutrients that the body can absorb and consume. The gut microbiome has been shown to have an essential role in molding the immune system and contributing to health and disease in the last ten years. Due to molecular mimicry, the hypothesis that foreign microbial peptides may exhibit structure and sequence characteristics with self-antigens and hence be capable of activating immune cell auto-reactivity, the microbiome is of special interest in autoimmunity.

The Gut Microbiota and Vitamin D:

A proper balance of micronutrients, vitamins, and minerals, including vitamin D, is essential for good health and disease control. Infantile rickets and adult osteomalacia are caused by vitamin D deficiency. Low vitamin D levels have been linked to an increased risk of hypertension, diabetes, peripheral artery disease, cardiovascular disease, certain cancers, and autoimmune and inflammatory diseases. Vitamin D deficiency is common, especially in areas with little sunlight exposure, and may impair normal intestinal homeostasis and barrier functions by influencing the tight junction architecture, bacterial colonization, and anti-inflammatory responses.

What Effect Does Vitamin D Deficiency Have on Intestinal Bacteria and Autoimmunity?

Vitamin D deficiency has shown an association with autoimmune illness by affecting the microbiota and immune system.

  • Vitamin D shortage or supplementation alters the microbiome, and changing the number or makeup of bacteria has an impact on disease manifestation.

  • Physical and functional barrier integrity can be compromised by a lack of vitamin D signaling caused by a dietary shortage or a genetic defect in VDR expression or activity. This allows germs to interact with the host, causing immunological responses to be stimulated or inhibited.

  • In the case of vitamin D insufficiency, our natural, intrinsic immune defenses may be weakened.

The Gut Microbiota Is Influenced by Vitamin D Supplementation:

Significant links have been discovered between vitamin D and the gut microbiota. During vitamin D supplementation, a shift in microbial composition was observed.

The Epithelial Barrier in the Gut Mucosa Is Protected by Vitamin D:

Vitamin D regulates gut mucosa homeostasis by maintaining the integrity of the epithelial barrier and healing the epithelium. Vitamin D protects the epithelial barrier by increasing the expression of VDR (vitamin D receptor) associated intercellular junction proteins, which form tight junctions between epithelial cells. Inadequate vitamin D levels increase the mucous membrane's susceptibility to damage, increasing the risk of inflammatory bowel disorder (IBD) significantly. Numerous studies have shown that patients with IBD frequently have vitamin D deficiency, even in remission. A low vitamin D level is an external risk factor for IBD exacerbation.

Bacteria Regulate VDR Expression in the Gut Microbiota and Their Fermentation Products:

Interactions between vitamin D and VDR help maintain gut homeostasis by preventing pathogen invasion, suppressing inflammation, and maintaining cell integrity. VDR expression and location may thus be regulated by both commensal and pathogenic gut microbiota. Probiotics can boost VDR expression and activity in the host, reducing intestinal inflammation.

Probiotic Bacteria Raise the Level of 25-Hydroxyvitamin D in the Blood:

Low levels of 25-hydroxyvitamin D in the blood have been linked to inflammatory bowel disease.


Vitamin D has anti-inflammatory and immune-modulating properties in the GIT (gastrointestinal tract). Many of these functions, which impact the human microbiome, occur as a result of complex ligand-receptor communication between vitamin D and VDR. Vitamin D is also involved in innate and adaptive immunity, intestinal barrier integrity, and gut homeostasis. Vitamin D regulates the gut microbiota because vitamin D deficiency causes a microbial imbalance in the GIT. Vitamin D's antibacterial effect is linked to the expression of antimicrobial peptides (AMPs). The gut microbiota responds to exogenous vitamin D, and some microbiota fermentation products can induce VDR expression.

Frequently Asked Questions


How Does Vitamin D Enhance Gut Health?

Intestinal barrier integrity and innate and adaptive immunity are regulated by vitamin D and its nuclear receptor. While vitamin D may affect the gut microbiota and have anti-inflammatory and immune-modulating effects, metabolites from the gut microbiota may also control nuclear expression.


How Does Vitamin D Reduce Inflammation in the Gut?

The integrity of the gastrointestinal tract's barrier, the monitoring of the gut microbiota, and inflammatory immune responses are all significantly influenced by vitamin D. These mechanisms are crucial for halting IBD's progression (intestinal bowel disease) and easing its symptoms.


How Do Gut Issues Result in Low Vitamin D Levels?

Bowel disease patients may have trouble absorbing dietary fat and are thus more likely to suffer from a vitamin D deficiency. People with Crohn's disease, untreated celiac disease, insufficient pancreatic enzymes, and those whose bowel has undergone partial removal are all vulnerable to this condition.


Which Vitamin D Is Ideal for Maintaining Gut Health?

The ideal vitamin is vitamin D3. The mechanism of immune responses and gut health depends on the vitamin D pathway. There is some evidence that vitamin D can control gastrointestinal inflammation. Epidemiological studies have shown that people with higher serum vitamin D levels have a lower incidence of IBD (inflammatory bowel disease), particularly Crohn's disease. 


What Are the 14 Indicators of Vitamin D Deficiency?

- Muscle pain.
- Fatigue.
- Painful bones.
- Low endurance.
- Sweaty head.
- Sleeping problems.
- Hair loss.
- Low mood.
- Heart issues.
- Slow healing wounds.
- Weight gain.
- Dizziness.
- Recurrent infections.
- Impairment of cognitive functions.


What Is the Effect of Vitamin D on IBS?

Vitamin D supplementation for six weeks helps IBS (inflammatory bowel syndrome) patients' symptoms and quality of life. Vitamin D supplementation appears to improve the IBS symptoms by addressing the condition's root causes.


Which Vitamin Helps to Repair the Gut Lining?

The top three scientifically supported supplements are:
- Probiotics. 
- L-Glutamine. 
- Vitamin D.


Does Vitamin D Aid in Gas and Bloating?

Stomach ache, bloating, gas, and other gastrointestinal symptoms significantly decreased with vitamin D administered every two weeks for six months.


What Gut Issue Begins With the Letter D?

The digestive conditions of diverticular disease and diverticulitis (colon) affect the large intestine. The diverticular disease causes the intestine's lining to develop tiny bulges or pockets known as diverticula.


How Can Vitamin D Improve Digestion and Sleep?

The role of vitamin D in regulating sleep is being increasingly supported by research. Improved sleep, less pain, and unexpected bowel symptom resolution were all seen after three months of taking vitamin D.


How Does Vitamin D Benefit Probiotics?

Probiotics may work synergistically with vitamin D by increasing the expression of vitamin D receptors. In people with vitamin D deficiency, probiotics and vitamin D may reduce inflammation and oxidative stress, enhancing hormonal profiles.


What Is the Initial Stage of Vitamin D Deficiency?

The first biochemical symptom is a slight increase in parathyroid hormone in vitamin D deficiency. This frequently happens before plasma calcium falls below the reference range.


What Is the Expected Timeframe for Feeling Better After Taking Vitamin D?

Vitamin D levels in the body typically rise after a few weeks of taking daily vitamin D supplements. After a few weeks, 1,000 IU of vitamin D3 taken daily is predicted to elevate blood levels of 25(OH)D by 10 ng/ml.
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Dr. C. Elanchezhian
Dr. C. Elanchezhian

General Medicine


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