Vitamin D’s role in gut health and in the prevention of intestinal diseases

Multiple studies have shown that vitamin D plays a key role in gut health by supporting the protective mucosa, the massive gut flora, the intestinal immune defense, and the regulation of inflammatory processes. According to a new review article published in Nutrients, lack of vitamin D, which is quite common, may therefore result in an increased risk of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD), which more and more people are affected by.

The digestive tract is the body’s largest organ in our digestive system and harbors the major part of our immune defense, which helps kill off harmful microbes and food toxins while controlling the enormous gut flora that harbors billions of different microorganisms. The gut flora plays a major role in breaking down our food and synthesizing vitamins, enzymes, neurotransmitters, lactic acid, and other important compounds. The gut flora and the immune system of the host must maintain the right balance to prevent potentially harmful bacteria and fungi from becoming dominant. Also, it is vital to prevent the immune attacks and local inflammatory processes from going into overdrive. If this delicate balance between the gut flora and the immune system is disrupted, it may cause gut flora imbalances, irritable bowel syndrome (IBS), and inflammatory bowel diseases (IBD) such as ulcerative colitis, and Crohn’s disease.
It is well known that antibiotics, excess sugar intake, unhealthy diets, and ageing can have a negative impact on the gut flora. The same goes for nutrient deficiencies, because both the gut flora and the immune defense need nutrients to function properly.
In their review article in Nutrients, the authors look at vitamin D’s role in all of this. Deficiencies of this vitamin are widespread and contribute to the growing rate of digestive problems and intestinal diseases. The following shows how vitamin D works in the gut flora and the immune defense:

• It is considered a steroid hormone and helps activate and regulate numerous gene activities
• All cells in the digestive tract have vitamin D receptors (VDR), indicating that vitamin D plays a key role in gut health
• Vitamin D is important for the maintenance and the integrity of the intestinal mucosa and the epithelial cells that form a protective barrier
• Vitamin D helps support and control the enormous gut flora, thereby ensuring that the beneficial microorganisms such as lactic acid bacteria and Bifido bacteria dominate, at the same time as suppressing potentially harmful microorganisms such as E. Coli, Streptococcus, and Candia Albicans
• Vitamin D regulates the gut flora, thereby relieving the immune defense
• Vitamin D supports different parts of the immune defense, including macrophages, T cells, and B cells that are all important for enabling the immune defense to attack and destroy microbes and toxins by means of “blitz attacks” or inflammatory reactions
• Once the harmful microbes and toxins have been eliminated, vitamin D controls and shuts down the inflammatory processes to prevent them from causing local tissue damage and chronic inflammatory gut diseases like ulcerative colitis and Crohn’s disease

Studies of vitamin D supplements and their impact on gut health

A healthy gut flora is able to synthesize lithocholic aid (LCA) that enhances the absorption of vitamin D from food. Supplementation with 1,250 (50,000 IU) of vitamin D once every week for 12 weeks has been shown to significantly improve the diversity of the gut flora. Studies of overweight individuals have found a positive relation between beneficial Bifido bacteria and vitamin D. On the other hand, researchers have observed that vitamin D receptors in several potentially harmful gut bacteria were dialed down. Genes play a huge role.
Patients with inflammatory bowel diseases have obtained a positive effect of taking 1,000 micrograms (40,000 IU) of vitamin D once every week for eight weeks. This also resulted in a reduction of CRP (C-reactive protein), which is an inflammation marker.
As described in the review article, several studies have been conducted where very large doses of vitamin D have been administered once weekly to patients with various gut disorders. This should always be done under the guidance of a health professional. The European Food Safety Authority (EFSA) has established a safe upper intake level of 100 micrograms of vitamin D daily.
Other studies of vitamin D supplementation have not shown similar results, but it is important to note that vitamin D only has a therapeutic effect on people who are deficient to begin with. Also, the dose that is used must be large enough to optimize blood levels of vitamin D. An optimal level should ideally be above 75 nmol/L, and it is even better if it is around 100 nmol/L.

Why vitamin D deficiency is so widespread in inflammatory bowel disease

The sun during the summer period is our primary source of vitamin D. We synthesize the nutrient in our skin when a cholesterol precursor is exposed to UV-rays. Interestingly, the highest rate of inflammatory bowel diseases is found at northern latitudes, where the sun during the winter period sits too low in the sky to enable vitamin D synthesis. Other factors that can reduce vitamin D levels are ageing, having dark skin, spending too much time indoors, overusing sun factor cream, genetic factors, overweight, type 2 diabetes, and the use of cholesterol-lowering drug (statins). It has also been found that patients with inflammatory bowel diseases have difficulty with absorbing vitamin D from oily fish, cod roe, eggs, dairy products, and other vitamin D sources. Therefore, these individuals have an increased need for this vitamin.

Inflammatory bowel diseases are associated with

• A derailed immune defense
• Dysbioses – which are imbalances in the gut flora
• Structural changes to the intestinal mucosa
• Unhealthy diets and the use of antibiotics
• Lack of vitamin D and/or other relevant nutrients

Referencer:

Jiaxin Wang et al. Contemporary Perspectives on the Role of Vitamin D in Enhancing Gut Health and Its Implications for Preventing and Managing Intestinal Diseases. Nutrients 2024

Lintao Dan et al. Circulating 25-hydroxyvitamin D concentration can predict bowel resection risk among individuals with inflammatory bowel disease in a longitudinal cohort with 13 years of follow-up. International Journal of Surgery. 2024

Antonia Topalova-Dimitrova et al. Lower vitamin D levels are associated with the pathogenesis of inflammatory bowel diseases. Medicine. 2023

Gominak SC. Vitamin D deficiency changes the intestinal microbiome reducing B Vitamin production in the gut. The resulting lack of pantothenic acid adversely affects the immune system, producing a “pro-inflammatory” state associated with atherosclerosis and autoimmunity. Med Hypotheses 2016