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Why You Need Vitamin D for Optimal Gut Health

Vitamin D has received a lot of attention lately, but new research is supporting the need for vitamin D in healthy digestive function. Unfortunately, many are not getting enough of this essential vitamin!

Image of healthy digestive tract without leaky gut

It is estimated that approximately 40 percent of Americans are deficient in vitamin D. A few reasons for this include lower dietary intake of vitamin D rich foods and insufficient exposure to sunlight, which is needed for our body to produce vitamin D.

Health Benefits of Vitamin D

Vitamin D has long been known to be essential for bone health by promoting calcium absorption and supporting other bone strengthening mechanisms in the body. However, during the past two decades researchers have found many other roles of vitamin D in supporting optimal health.

In addition to bone health, Vitamin D has been shown to play a role in the following:

  • Immune system support

  • Antimicrobial defense

  • Detoxification

  • Reduction of oxidative stress

  • Neuroprotective function

  • Anti-inflammatory action

  • Anti-cancer function

  • Cardiovascular support

Diseases Associated with Vitamin D Deficiency

If you search the scientific literature for "vitamin D deficiency and disease," over 30,000 published studies result from the search! While this research is ongoing, here is a sample of what the science has found to date...

Vitamin D deficiency is associated with:

  • Increased risk for Inflammatory Bowel Disease (IBD) such as Crohn's Disease or Ulcerative Colitis

  • 30-50 percent increased risk for colon, breast, and prostate cancer (based on population studies)

  • Increased risk for cardiovascular disease, including high blood pressure

  • Increased risk for diabetes

  • Increased risk for other autoimmune diseases such as rheumatoid arthritis

  • Increased risk for depression, Alzheimer's disease, epilepsy, and cognitive decline

  • Increased risk for multiple sclerosis, psoriasis, and chronic kidney disease

Role of Vitamin D in Gut Health

While there are many factors that affect the gut microbiome and overall gut health, one that is frequently overlooked is vitamin D. Everyone should have their vitamin D level checked at their annual blood draw and deficiencies should be addressed with supplementation due to its role in the above diseases. In addition, those who have digestive health conditions such as Irritable Bowel Syndrome (IBS) or Inflammatory Bowel Disease (IBD) may want to follow up with a 6-month vitamin D check to ensure adequate blood levels.

3 Ways Vitamin D Supports a Healthy Gut

1. Vitamin D promotes a healthy microbiome.

Research shows vitamin D deficiency is associated with an imbalance of microbes in the gut, called dysbiosis. Whenever dysbiosis is present in the gut, negative health symptoms (e.g., GI upset or irregularity, poor immune function, etc.) may occur or it can contribute to disease in the long term. A recent study has shown that vitamin D supplementation in vitamin D deficient adults can increase the diversity of microbes in the gut and result in a greater population of health-promoting gut microbes.

2. Vitamin D supports the intestinal barrier lining.

Vitamin D promotes healthy tight junctions in the intestinal lining, which is the space between intestinal cells. In other words, it helps prevent the gaps between cells which can lead to leaky gut syndrome, or increased intestinal permeability. Leaky gut leads to many negative symptoms, such as bloating, constipation, diarrhea, fatigue, headaches, confusion, difficulty concentrating, joint pain, skin problems, and others. For more information on leaky gut syndrome, see my blog article on What is Leaky Gut.

3. Vitamin D prevents immune overreaction at the gut level.

Imbalance of gut microbes (dysbiosis) has been found to be a potential trigger for autoimmune disease. While vitamin D has been shown to promote healthy gut microbial balance, it has also been shown to promote normalized immune function in the gut. This may have a broader health benefit beyond gut health as approximately 70 percent of our immune system resides in the gut. For more information on this topic, see my blog article A Strong Immune System Requires a Healthy Gut.

Food Sources of Vitamin D

Vitamin D is found in several food sources, but it is not widespread. The following are primary food sources of vitamin D:

  • Fish (salmon, mackerel, tuna, sardines)

  • Fortified milk and fortified milk substitutes

  • Egg yolks

  • Fortified cereals (read the Nutrition Facts panel for vitamin D content)

The body can also produce vitamin D from UV sunlight exposure. However, many of us wear sunscreen or spend the majority of our time indoors and therefore do not get enough sun exposure to produce significant vitamin D. In addition, from November through March, the UV rays are not strong enough to produce vitamin D in those living in latitudes north of Atlanta, GA.

Most healthcare professionals recommend getting 2,000 IU of vitamin D daily, or higher levels if your blood test shows you have a deficiency, or insufficiency. For those who do not consume vitamin D-rich foods on a daily basis, supplementation is recommended.

Tips for Supplementing With Vitamin D

Your supplement should contain the active form of vitamin D, which is Vitamin D3 (cholecalciferol). Always choose a supplement that is manufactured in an FDA-registered facility that follows certified Good Manufacturing Practices (cGMP). If you suffer from a gut health condition or symptoms, then choose a supplement that is free of potential allergens (wheat, gluten, dairy, etc.). If you are not sure which supplement is best for you, consult a Registered Dietitian Nutritionist (RDN) for assistance. Your recommended supplement dosage will depend on several factors - your current vitamin D blood level, dietary intake, and UV light exposure to name a few. If you don't have a current lab value for vitamin D, then starting with 1,000-2,000 IU of supplemental vitamin D may be a good idea until you can get your blood level checked. Ask your physician to add vitamin D to your next lab draw, or you can purchase a home test kit with a simple finger prick for quick results.

The Bottom Line

Vitamin D is an essential nutrient that plays a significant role in many aspects of our health, including digestive wellness! Research shows that many Americans are deficient, or have insufficient blood levels of vitamin D for optimal health! Vitamin D deficiency is relatively easy to correct and may have a significant impact on your risk for disease and digestive symptoms.

Start with data and get your blood vitamin D level checked. If you're not due for a physician's visit in a while, consider investing in a home test kit with a simple finger prick so you can adjust your dietary and/or supplement intake of vitamin D accordingly.

If you need help with understanding your personal need for vitamin D, or if you're looking for diet and lifestyle strategies to improve gut health problems, consult a Registered Dietitian Nutritionist (RDN) who specializes in digestive health. You may also book an Introductory Call with Kirkman Nutrition to see if my program/services can help you.


Parva, Naveen R et al. “Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011-2012).” Cureus vol. 10,6 e2741. 5 Jun. 2018, doi:10.7759/cureus.2741.

Gil, Ángel et al. “Vitamin D: Classic and Novel Actions.” Annals of nutrition & metabolism vol. 72,2 (2018): 87-95. doi:10.1159/000486536.

Wang H, Chen W, Li D, Yin X, Zhang X, Olsen N, Zheng SG. "Vitamin D and Chronic Diseases." Aging Dis. 2017 May 2;8(3):346-353. doi: 10.14336/AD.2016.1021. PMID: 28580189; PMCID: PMC5440113.

Fletcher J, Cooper SC, Ghosh S, Hewison M. "The Role of Vitamin D in Inflammatory Bowel Disease: Mechanism to Management." Nutrients. 2019 May 7;11(5):1019. doi: 10.3390/nu11051019. PMID: 31067701; PMCID: PMC6566188.

Battistini, Carolina et al. “Vitamin D Modulates Intestinal Microbiota in Inflammatory Bowel Diseases.” International journal of molecular sciences vol. 22,1 362. 31 Dec. 2020, doi:10.3390/ijms22010362.

Kellermann A, Jensen KB, Bergenheim F, et al. "Mucosal Vitamin D Signaling in Inflammatory Bowel Disease." Autoimmunity Reviews. 2020; 19 (11) ISSN 1568-9972,

Singh, Parul et al. “The potential role of vitamin D supplementation as a gut microbiota modifier in healthy individuals.” Scientific reports vol. 10,1 21641. 10 Dec. 2020, doi:10.1038/s41598-020-77806-4.

De Oliveira, Gislane Lelis Vilela et al. “Intestinal dysbiosis and probiotic applications in autoimmune diseases.” Immunology vol. 152,1 (2017): 1-12. doi:10.1111/imm.12765.

U.S. Department of Agriculture, Agricultural Research Service. Food Data Central, 2019.

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