For many of us, as we roll into the winter months it means less sunshine, extra layers of clothing, and a lot more time indoors. But as cozy as a winter night curled up inside might sound, this lack of sunshine can lead to something much less welcoming – a vitamin D deficiency.

This mighty molecule – also dubbed “the sunshine vitamin” – is a key player in everything from your bone health to how your cells grow. But more and more research is finding out just how important vitamin D is to one of the most complex networks in your entire body – your immune system.

Today we’re going to dive into exactly what role vitamin D plays in regulating your immune system, what happens if you’re deficient in this nutrient, and most importantly – how to ensure you’re getting enough of this essential vitamin.

What Is Vitamin D?

Vitamin D functions as both a nutrient you eat and a hormone your body produces. Some vitamin D can be obtained through your diet and absorbed through your digestive tract, and the rest is produced by your body. You see, when your skin is exposed to UV rays from the sun, it triggers a chemical reaction that induces vitamin D synthesis. 

Once obtained – whether via ingestion or through UV rays – vitamin D must be activated to be utilized by the body. This initial form of vitamin D must undergo a process known as hydroxylation in both the liver and kidneys.¹ From there it’s metabolically active and can be used by the body. 

Let’s take a look at exactly what the body uses this active form of vitamin D for.

What Exactly Does Vitamin D Do in the Body?

Vitamin D is essential for a number of critical functions in your body, such as: ^2,3

• Calcium and phosphorus absorption
• Bone mineralization
• Regulation of cellular growth and differentiation
• Aiding in glucose metabolism and regulating insulin levels
• Neuromuscular function

But one of vitamin D’s most fascinating and most important functions is the role it plays in regulating and balancing your immune system.

Vitamin D and Your Immune System

Vitamin D plays a complicated and intricate role in the way your immune system functions. Let’s take a detailed look at the exact interplay between vitamin D and some of the key components that make up your immune system:⁴

Vitamin D Enhances the Function of Macrophages and Monocytes

Vitamin D enhances the natural antimicrobial action of both monocytes and macrophages. Vitamin D accomplishes this by activating these immune cells – stimulating them to produce an antimicrobial compound known as cathelicidin. This upregulation of cathelicidin aids in fighting foreign invaders by:

• Destabilizing microbial membranes
• Disrupting viral envelopes
• Altering the viability of host target cells

Vitamin D also triggers cathelicidin to exit monocytes and macrophages in order to prompt the recruitment of nearby lymphocyte cells.

Vitamin D Modulates Antigen-Presenting Cells

Antigen-presenting cells – such as dendritic cells, macrophages, and B cells – collect and break down antigens (foreign substances).⁵ Once broken down these antigens are then presented to other immune cells in order to orchestrate a targeted adaptive immune response. 

Vitamin D has been found to modulate antigen-presenting cells by causing them to become more immature and tolerogenic – resulting in decreased antigen presentation and less immune stimulation. This subsequently triggers an increase in the production of the tolerogenic cytokine IL-10, while suppressing the production of inflammatory cytokines like IL-2, IL-6, and IL-17.

In simpler terms, vitamin D promotes immune tolerance – helping your body resolve the effects of inflammation.

Vitamin D Regulates Endothelial Function and Vascular Permeability

One of the cardinal side effects of inflammation triggered by an immune response is increased vascular permeability. To induce vascular permeability your endothelial cells – the cells that line your blood vessels – essentially contract and create “gaps” to increase the passage of substances.⁶

Vitamin D and its metabolites have been found to have a protective effect against vascular dysfunction and prevent any injury to tissues caused by this local snd systemic inflammation.

Vitamin D Promotes a Healthy Gut-Immune Axis

Your gut and your immune system are intricately linked. Both the integrity of your gut lining and the composition of your gut flora play a critical role in your immune function and ability to respond to perceived threats. Vitamin D helps promote healthy communication and balance between your gut and your immune system by:

• Promoting mucosal barrier function through enhancement of the proteins that hold your epithelial cells together
• Increasing the number of proteins responsible for recognizing and identifying pathogens 
• Inducing the secretion of antimicrobial peptides via specialized epithelial cells in your gut known as Paneth cells
• Limiting the translocation of gut bacteria out of your digestive tract

This combination packs a powerful punch when it comes to maintaining homeostasis in your gut – and subsequently your immune system.

Vitamin D Controls T and B Lymphocytes

Studies have found that vitamin D can modulate T and B lymphocytes – shifting them from a pro-inflammatory state to a more tolerogenic state via:

• Suppressing proliferation of T lymphocytes
• Modulating pro-inflammatory cytokine production
• Promoting differentiation of regulatory T cells
• Inhibiting immunoglobulin synthesis
• Inducing apoptosis of activated B cells
• Impeding B cell activation 

This combination of influences on T and B lymphocytes means vitamin D plays an important role in the suppression and “ramping down” of the immune response.

What Happens When Your Vitamin D is Low?

Inadequate intake of vitamin D can have serious implications for your overall health – but especially for your immune system. Considering vitamin D plays such a critical role in your immune function, it’s no surprise that a vitamin D deficiency can lead to a number of conditions that are immune-mediated. Chronic low levels of vitamin D have been linked to life-altering conditions including:⁷

• Psoriasis
• Type 1 diabetes
• Multiple sclerosis
• Inflammatory bowel disease
• Rheumatoid arthritis
• Cancer

But a vitamin D deficiency doesn’t just contribute to chronic conditions – it also has a monumental impact on how well your body is able to deal with an acute infection. Low vitamin D levels have been directly linked to an increased risk of infection, and an increased likelihood of more severe and prolonged infections.⁸

Clearly, getting enough vitamin D in your life is essential for your overall health. So that’s probably got you wondering exactly how you can be sure you’re getting enough vitamin D on a daily basis – especially in these cold winter months.

So, How Can I Increase My Vitamin D Levels?

Thanks to modern lifestyle practices, the vast majority of us are deficient in vitamin D. But the good news is, there are some simple ways to incorporate more of this immune-boosting nutrient into your life. Here’s what I recommend:

• Get some sunshine: While this may be dependent on your location and the season, try to get at least a little bit of sunshine each day. 
• Eat foods rich in vitamin D: Foods that are chock-full of healthy vitamin D include:
  • Fatty fish
  • Seafood
  • Egg yolks
  • Mushrooms
• Take a vitamin D supplement: In modern times, it can be challenging to get an adequate amount of vitamin D from sunshine and diet alone. So taking a vitamin D supplement is often one of the best ways to fill in any gaps. 
• Support healthy absorption of vitamin D: Having a healthy gut that can properly absorb any of your dietary intake of vitamin D is crucial. So make sure you’re prioritizing your gut health for optimal absorption. Click here to learn more about how you can optimize your gut health. 
• Reduce your toxic burden: An accumulation of toxins in your body can throw off your cell’s ability to properly process toxins and can burn out your immune system – further depleting your vitamin D levels. So taking steps to reduce your overall toxic burden is critical – click here to learn exactly what steps to take to start reducing your toxic burden. 

My online store is full of supplements that can help support healthy vitamin D levels. Whether you simply need a vitamin D supplement, need help healing your gut, or are looking for ways to minimize your toxic burden – I’ve got you covered. Click here to visit my online store now – and click here if you want to get 10% off your first order.

Set Yourself Up for Success

Your immune system is like the guardian of your galaxy – it’s your very best defense against potentially harmful foreign pathogens and toxins. So setting your immune system up for success is one of the most important things you can do to optimize your health and promote radiant health for years to come. And one of the very best ways you can show your immune system some love is to ensure you’re getting plenty of vitamin D on a daily basis. 

If you enjoyed this article, head over and check out my blog – it’s chock-full of my most up-to-date and easy to understand research to help you take the driver’s seat when it comes to your health. And if you’re ready to take it even deeper, I encourage you to sign up for my newsletter to get my very best advice delivered straight to your inbox. All you have to do is enter your name and email address in the form below. 

Now it’s time to hear from you. Were you surprised to hear what a monumental role vitamin D plays in your immune system? What steps are you taking to ensure you and your loved ones have healthy vitamin D levels?

References:

1. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1240026/
3. https://academic.oup.com/ajcn/article/80/6/1689S/4690513
4. https://www.mdpi.com/2072-6643/12/7/2097/htm
5. https://www.sciencedirect.com/topics/veterinary-science-and-veterinary-medicine/antigen-presenting-cell
6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4526869/#:~:text=Retraction%20of%20the%20endothelial%20cell,facilitates%20opening%20of%20paracellular%20junctions.
7. https://www.mdpi.com/2072-6643/12/7/2097/htm
8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3756814/