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We’re all looking for ways to support our health and our immune system. A strong immune system can fight off harmful pathogens, support wound healing, and boost your vitality. While healthy eating and regular exercise can fortify your immune system, it’s also essential to ensure your body gets the nutrients it needs to function optimally. 

That said, you may be wondering about vitamin D immune system support—does it really help? The simple answer is yes, vitamin D and immune system functions are closely connected.1 

Let’s take a deeper look at how you can use vitamin D to support your immune system and keep it in peak condition.

What Does Vitamin D Do?

Medical researchers have long known that vitamin D is crucial to building strong bones in childhood, as well as maintaining bone density in adulthood.2 

But within the last few years, our understanding of vitamin D has expanded. Researchers have found vitamin D receptors in many areas of the body beyond the skeletal system, including the kidneys, pancreas, intestines, platelets, prostate, and immune cells. 

This tells us that vitamin D must play a part in many other functions throughout the body.2 

Some of vitamin D’s roles in the body include supporting:

  • Healthy bone development and maintenance at all life stages – If you’re wondering how to boost your kid’s immune system, you’re not wrong to give vitamin D a try, but its benefits don’t stop at just immune health. In childhood, vitamin D is key to proper bone formation. In adults, vitamin D helps prevent bone density loss and osteoporosis.3
  • Nutrient absorption – One of the reasons it’s so crucial to bone health is that vitamin D is used in the intestinal tissues to aid in the absorption of calcium and phosphorus, ensuring that your body can maintain normal levels of these nutrients in your bloodstream.4
  • Gut health – Vitamin D is involved in regulating the biome of the intestines and helps to maintain a healthy colony of microbes residing in the gut. Science is still uncovering the connections between vitamin D and intestinal health, but there’s growing evidence that vitamin D helps by strengthening the intestinal barrier and balancing intestinal flora.5
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How Is Vitamin D Connected to Immune Function?

Researchers are still learning exactly how the vitamin D immune system connection works. But what we do know is that most immune cells have vitamin D receptors, and vitamin D interacts with these cells to stimulate their virus-fighting response.6 

Many studies have found that supplementing with vitamin D may reduce the risk of respiratory infections like the flu.6 Some studies have found this to be especially helpful in winter when vitamin D deficiencies are most prevalent due to lack of sun exposure.7 So, if you’re thinking about which vitamins to take when sick, vitamin D can be beneficial. 

But vitamin D doesn’t just help immune cells fight off invaders. It also acts to modulate the reaction of the immune system, preventing the overreaction to pathogens that can lead to inflammatory conditions.8 For that reason, an adequate vitamin D level is important for immune response and function.

Will Vitamin D3 Help Your Immune System?

Vitamin D is often referred to interchangeably with its other forms, vitamin D2 and vitamin D3. 

Luckily for us, we don’t need to worry about the different forms of vitamin D—our bodies take care of converting any form of vitamin D into the active form, vitamin D3. 

Any cells in your body that use vitamin D can produce an enzyme that transforms vitamin D into vitamin D3.2 Immune cells produce this enzyme, which is one of the clues researchers uncovered that tells us vitamin D may be closely involved with the immune system.

Where Does Vitamin D Come From?

Although vitamin D is one of the nutrients that your body can produce on its own, according to data from the National Institutes of Health (NIH), up to 25% of people are still deficient. 

Vitamin D from dietary sources is very limited.3 Mushrooms are a plant source of vitamin D. But even these sources don’t contain much vitamin D—to get enough, you’d have to eat them almost daily.10

In light of all this, supplements and fortified foods are a good option for many people, particularly those with plant-based diets.3 Common fortified food sources include:

  • Whole grain breakfast cereals 
  • Orange juice
  • Soy, nut, and oat milks

How Much Vitamin D Do You Need?

This is another area where medical professionals still haven’t quite come to a conclusion. Different countries have different agreed-upon recommendations for vitamin D sufficiency and intake levels.

Currently, the NIH recommends that adults ages 19 to 70 should get 15 micrograms, or 600 International Units (IU) per day. People over 70, especially women in menopause, need a bit more (about 800 IU).9

It’s possible to get too much vitamin D as well as too little. The upper limit for adults as suggested by the NIH is 100 micrograms, or 4,000 IU.3

Can You Get Enough Vitamin D From the Sun?

You've probably heard people say sunshine helps a low vitamin D level. Vitamin D is often called the sunshine vitamin because your body uses a protein in the skin to synthesize UVB rays naturally. Most of us produce at least some vitamin D in this way. 

However, many factors limit the amount of vitamin D your body can make from sunlight absorption:

  • Sun filtered through windows limits vitamin D production
  • Natural vitamin D production declines with age
  • Darker skin tones produce less vitamin D from sunlight and may require hours of sun exposure to produce sufficient amounts
  • Clouds, fog, and smog all reduce the amount of UV light available to your skin
  • 30% or more of the skin’s surface needs to be exposed to absorb sufficient UVB light—which is not easy to manage in cold climates10

It’s very important to balance your body’s need for sunlight with skin safety. Too much exposure to UV radiation damages your skin, leading to premature wrinkles, changes in skin tone and texture, and greatly increasing your risk of skin cancer.9 Cover up with sun-protective clothing, and remember your sunscreen.  

Vitamin D Deficiency

While vitamin D has been believed to help with immune health and other functions of the body, deficiencies in vitamin D have been linked to a variety of health problems. Recent research has even indicated that people with lower levels of vitamin D in their bloodstream appeared to be at higher risk of contracting COVID-19.11 

Other conditions that are or may be connected to low levels of vitamin D include:

  • Improper bone development – Deficiency in children can lead to conditions like rickets, in which the bones are soft, malformed, and painful.3
  • Increased risk of osteoporosis – In adults, low levels of vitamin D are strongly associated with loss of bone density and increased risk of fractures.3
  • Increased risk of autoimmune disorders – There also appears to be a link between vitamin D deficiency and autoimmune disorders such as arthritis, asthma, and diabetes, but research into this connection is still ongoing.12
  • Inflammatory bowel disease – Deficiency in vitamin D is common among sufferers of inflammatory disorders of the bowels, such as Crohn’s disease and ulcerative colitis.  Low levels of vitamin D may increase the risk of flare-ups and relapses. 

How to Get More Vitamin D In Your Routine

So the question becomes how to tackle low Vitamin D levels. According to the NIH, because so few foods contain vitamin D, most Americans get their vitamin D from supplements and fortified foods. 

If you opt for a vitamin D supplement, here are a few points to note:

  • Vitamin D2 vs. vitamin D3 – Vitamin D supplementation is available as either vitamin D2 or vitamin D3. Either form is absorbable, but vitamin D3 is believed to raise blood levels of vitamin D higher and sustain them longer than a vitamin D2 supplement.3 
  • Take with food – Vitamin D is one of the fat-soluble vitamins, so the NIH recommends taking your vitamin D supplement with a meal that includes some fat in order to help with absorption. 
  • Choose a supplement with bioavailable nutrients – Not all supplements are created equal, and with so many choices on the market, it can be difficult to know what to look for. Bioavailability is one of the most critical factors in selecting a supplement, since not all formulations are equally absorbable by the body.12 
  • Choose a formulation with vitamin k – Vitamin D has been shown to work synergistically with vitamin K to increase your body’s ability to metabolize and absorb calcium from foods. While vitamin D helps your body break down calcium and put it into your bloodstream, it’s vitamin K’s role to control where that calcium goes. Calcium in your bloodstream can accumulate in soft tissues, rather than going toward strengthening your teeth and bones. It’s thought that combining vitamin K with vitamin D prevents calcification of soft tissues such as arteries.3

Boost Your Wellness Routine With Cymbiotika

Vitamin D is a vital part of whole-body wellness. It supports everything from the health of your bones to the functioning of your immune system. Eating a varied diet with plenty of fresh, minimally-processed foods is always a good idea, but with the limited food sources of vitamin D, an immune defense supplement may be a wise choice.

Vitamin D3 + K2 + CoQ10 from Cymbiotika is a natural way to make sure your immune system has the vital nutrients it relies on to keep you well. 

Our plant-based, bioavailable products have simple ingredients you can understand, so you know you’re getting exactly what you need to support peak immune function without preservatives, additives, GMOs, or other unnecessary ingredients. 

Feel your best every day with Cymbiotika.


  1. Journal of Investigative Medicine. Vitamin D and theimmune system. 
  2. Nutrients. Vitamin D: nutrient, hormone, and immunomodulator.  
  3. National Institutes of Health Office of Dietary Supplements. Vitamin D.
  4. Endotext. Calcium and Phosphate Homeostasis. 
  5. Journal of Inflammation Research. The role of Vitamin D in immune system and inflammatory Bowel Disease. 
  6. Epidemiology and Infection. Epidemic influenza and vitamin D. 
  7. American Journal of Clinical Nutrition. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren.  
  8. Journal of Inflammation Research. Vitamin D and inflammatory diseases.  
  9. Yale Medicine. Vitamin D myths 'D'-bunked. 
  10. Journal of Investigative Dermatology. Recommended summer sunlight exposure levels can produce sufficient (> or =20 ng ml(-1)) but not the proposed optimal (> or =32 ng ml(-1)) 25(OH)D levels at UK latitudes. 
  11. PLOS ONE. Pre-infection 25-hydroxyvitamin D3 levels and association with severity of COVID-19 illness. 
  12. Medicina. Bioavailability of different Vitamin D oral supplements in laboratory animal model.  
  13. International Journal of Endocrinology. Synergistic interplay between Vitamins D and K for bone and cardiovascular health: a narrative review. 

by Isaac Otero / Aug 06, 2022