How Vitamin D Supports Kid-Friendly Immune Systems

Vitamin D

In our quest to improve our children’s health, one essential nutrient stands to me - vitamin D. It’s known as the “sunshine vitamin”, and while often thought of most for bone health, its significance goes well beyond that. Research has unveiled a crucial role that Vitamin D plays in bolstering the immune system in children.  As we continue to learn more, it becomes more evident that this nutrient is a key player in maintaining the well-being of our little ones.

What is Vitamin D?

First let’s talk about what vitamin D is. It’s a fat soluble vitamin which is found in foods. But unlike other vitamins we consume, we can also make vitamin D when ultraviolet light from the sun hits our skin. Many diets are poor in vitamin D, and many people live in areas where there are large parts of the year where it’s harder to synthesize vitamin D through their skin. In fact, worldwide an estimated 1 billion people have inadequate levels of vitamin D in their blood, and deficiencies can be found in all ethnicities and age groups. (1)

Vitamin D has many roles in our body. For our bones it helps support calcium and phosphorus absorption and retention, which is needed to build bones. This is why Vitamin D is critical for kids who are growing. Vitamin D plays other roles too, such as with reducing inflammation, reducing cancer cell growth and in fighting infections.

What does the Research Say for How Vitamin D Helps Our Kids' Immune Systems?

There is increasing evidence that vitamin D plays a role in keeping our kids well.  And even though interactions between nutrients and the immune system are complex, there appears to be numerous areas throughout our immune systems that vitamin D may have a positive role. Here’s how this vitamin may potentially play a role in supporting your child’s immunity:

  1. It enhances your kids' microbial defenses. It’s a regulator of what’s known as our innate immune system, which is composed of physical and other barriers that are our first line of defense against infection. One way it has influence is by enhancing the production of antimicrobial peptides which is one of our defenses against pathogens (the bad guys that cause infections). (2,3,4)
  2. It modulates your kids' immune cells. It influences how T-cells work (one type of immune cell), part of our adaptive immune system, which is our second line of defense against infections. Vitamin D helps regulate a balance between pro-inflammatory and anti-inflammatory responses, which is important to keep the immune system working effectively to defend itself when necessary, but not cause unnecessary harm. (3,4,5,6,7)
  3. It reduces respiratory infections. By supporting respiratory health, Vitamin D plays a crucial role in reducing the risk and severity of these infections, ensuring that kids can breathe easy and stay active. (8,9)

What Foods Have Vitamin D?

Few foods are naturally rich in vitamin D. Here's a run down of where you can find vitamin D in food:

  • The best sources are the flesh of fatty fish (salmon, tuna, trout, mackerel and sardines) and fish liver oils.
  • Smaller amounts are found in egg yolks, cheese, and beef liver.
  • Certain mushrooms contain some vitamin D. In addition some commercially sold mushrooms contain higher amounts of D due to intentionally being exposed to high amounts of ultraviolet light.
  • Many foods and supplements are fortified with vitamin D like dairy products (mainly just milk), cereals and orange juice.

You can see that there are not a ton of options, so your child would likely need to drink 2-3 cups of milk plus eat fatty fish or UV treated mushrooms daily to adequately meet their vitamin D from foods alone.


How Much Vitamin D Do Kids Need?

Many studies point to those who are deficient and take vitamin D have the most impact on their immune systems. So how much do kids need? See the chart below for recommendations. 

Age Group

Recommended Amount of Vitamin D

Toddlers (1-3 years old)

600 IU

Young Kids (4-8 years old)

600 IU

Older Kids (9-13 years old)

600 IU

Even older Kids (14-18 years old)

600 IU

But remember we get vitamin D from the sun too, so that may influence whether your kids need to take additional vitamin D, even if just at certain times of year, like in the winter. Those most at risk for vitamin D deficiency live at higher latitudes, have darker skin, are obese, are elderly, breastfed babies, and those with limited sun exposure. It’s worth noting here that sunscreen limits the absorption of vitamin D, so if your kids are covered head to toe in sunscreen at all times (which is good for skin cancer prevention), then you also would likely want to consider giving your child a supplement.

Supplements come both as vitamin D3 (primarily from animal sources) and D2 (primarily from plant sources). Both are converted to the active form of vitamin D in the body, but vitamin D3 tends to be more potent and is the form that is naturally produced in the skin when exposed to ultraviolet light. 

There is potential to take too much vitamin D. Vitamin D toxicity affects calcium absorption causing nausea, vomiting, muscle weakness, kidney stones, heart abnormalities and kidney damage. The recommended upper limit for children 1-3 years old is 2500 IU, for 4-8 years old it’s 3000 IU and for ages 9 and up 4,000 IU. You should not regularly give your child more than these amounts unless prescribed by your child’s doctor. For most children, I recommend a supplement that is between 600-1000 IU, unless there is a documented deficiency. 

In conclusion, there is plenty of evidence that vitamin D supports your child’s immune system. If your child is deficient in vitamin D and they correct that deficiency, this has the most potential to affect their immunity. Some things you can do to ensure they are getting enough vitamin D, is to double check they are drinking milk or a milk alternative with vitamin D added, give them weekly servings of fatty fish, and allow for daily sun exposure of about 15-30  minutes without sunscreen. You can always give, via supplements, the RDA for the recommended amount of Vitamin D to make sure they are getting enough. And if you have any doubts, checking vitamin D levels is a simple blood test that can let you know if your child needs more. 


Do you want to know what other nutrients can potentially benefit your child's immune system? We talked  about vitamin C and zinc in previous blog posts.

If you need supplements, you can order them from our Full Script store and have them shipped to you. We have created a shared Immunity Plan with recommendations for Vitamin D, vitamin C, zinc and more specially for kids.


  1. Lips PT. Worldwide status of vitamin D nutrition. The Journal of steroid biochemistry and molecular biology. 2010 Jul 1;121(1-2):297-300.
  2. Mailhot G, White JH. Vitamin D and Immunity in Infants and Children. Nutrients. 2020 Apr 27;12(5):1233. 
  3. Barlow P.G., Svoboda P., Mackellar A., Nash A.A., York I.A., Pohl J., Davidson D.J., Donis R.O. Antiviral Activity and Increased Host Defense against Influenza Infection Elicited by the Human Cathelicidin LL-37. PLoS ONE. 2011;6(10):e25333. 
  4. Wu Z, Liu D, Deng F. The Role of Vitamin D in Immune System and Inflammatory Bowel Disease. J Inflamm Res. 2022 May 28;15:3167-3185. 
  5. Bhalla AK, Amento EP, Clemens TL, Holick MF, Krane SM. Specific high-affinity receptors for 1,25-dihydroxyvitamin D3 in human peripheral blood mononuclear cells: presence in monocytes and induction in T lymphocytes following activation. J Clin Endocrinol Metab. 1983 Dec;57(6):1308-10.
  6. Bhalla A., Amento E., Serog B., Glimcher L. 1, 25-Dihydroxyvitamin D3 inhibits antigen-induced T cell activation. J. Immunol. 1984;133:1748–1754. 
  7. von Essen MR, Kongsbak M, Schjerling P, et al. Vitamin D controls T cell antigen receptor signaling and activation of human T cells. Nat Immunol. 2010;11:344–349. 
  8. Martineau AR, Jolliffe DA, Hooper RL, Greenberg L, Aloia JF, Bergman P, Dubnov-Raz G, Esposito S, Ganmaa D, Ginde AA, Goodall EC. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017 Feb 15;356:i6583.
  9. Martineau AR, Jolliffe DA, Hooper RL, Greenberg L, Aloia JF, Bergman P, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i6583.
  10. Srivastava SB. Vitamin D: Do We Need More Than Sunshine? Am J Lifestyle Med. 2021 Apr 3;15(4):397-401.
  11. The Nutrition Source from the Harvard School of Public Health
  12. Vitamin D Fact Sheet from the National Institutes of Health
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