How vitamin D supports immune health

sunlight beaming through a leaf

Whether your winter sweaters are still tucked away or you’re already bundling up, the arrival of cooler air has most of us looking for ways to support our immune systems. While Vitamin C and Zinc are usually top of mind during cold and flu season, getting enough Vitamin D should also be high on your list. Here’s why vitamin D can help strengthen your immune system this season. 

What is Vitamin D? 

Vitamin D plays a key role in many bodily functions, including maintaining your bones, mood, brain and immune health. It’s a fat-soluble vitamin, meaning it needs fat in order to be absorbed or moved to different cells in your body. It’s also stored in your fat cells so if your vitamin D intake is low (like during winter months) your body has a backstock. You may have heard of vitamin D being referred to as the “sunshine vitamin”. That’s because your body can convert the sun’s UVB rays into vitamin D.  

Two forms of vitamin D 

If you walk down the supplement aisle, you’ll find two different types of vitamin D – vitamin D2 and vitamin D3. Vitamin D2 is only found in plant foods like mushrooms whereas D3 is typically found in animal foods like sardines or fish liver. Both types will help you meet your daily needs, but when placed head-to-head, there’s a clear winner: vitamin D3. Vitamin D3 is better at raising your blood levels because it is more easily absorbed than D2.  

Vitamin D and your immune system 

Vitamin D is a bit of an unsung hero when it comes to strengthening your immune system. One of its lesser-known benefits is that it supports both your innate and adaptive immune response. Innate immunity is your first line of defense – it destroys anything in your body that doesn’t belong. Adaptive immunity combats foreign pathogens using notes and skills from previous encounters.  

Vitamin D helps stimulate the production of T cells, which are white blood cells that are part of your immune response. These cells are found throughout your body, including your upper and lower respiratory tract, and an increased production can better help your body fight against foreign invaders, infections, harmful bacteria and viruses.   

In other words: your immune cells need vitamin D to properly respond to threats and keep things like the common cold at bay. 

Vitamin D sources  

You’ve probably heard it before: spend 15-20 minutes outside to get your daily dose of vitamin D. While this may be a good rule of thumb during the summer months, fewer hours of sunlight during the cold weather can make it harder to meet your daily needs. And despite your body’s ability to naturally obtain vitamin D from sunlight, about 42% of people worldwide aren’t getting enough, so it’s best to regularly check with your healthcare provider to make sure you’re within a healthy range.  

To up your vitamin D intake at the table, add: 

  • Salmon 
  • Cod liver oil 
  • Eggs 
  • Mushrooms 
  • Fortified orange juice 

For more vitamin D food options, read Top 5 foods to boost your immune system.  

About Gabby    

Gabby is a nutritionist with a master’s degree in strategic communications. She loves using her nutrition-fluency with storytelling to encourage positive change. Before Persona, she worked at a mental health clinic helping clients manage stress, anxiety and other mental health issues through diet.     

Do you have questions about supplements? Reach out to one of our experts, or take Persona’s free nutrition assessment, and learn exactly what you need to take your wellness to the next level.      

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.       
This information is not intended as a substitute for the advice provided by your physician or other healthcare professional, or any information contained on or in any product label or packaging. Do not use the information from this article for diagnosing or treating a health problem or disease, or prescribing medication or other treatment. Always speak with your physician or other healthcare professional before taking any medication or nutritional, herbal, or homeopathic supplement, or using any treatment for a health problem. If you have or suspect that you have a medical problem, contact your health care provider promptly. Do not disregard professional medical advice or delay in seeking professional advice because of something you have read in this article.    



  1. Aranow C. Vitamin D and the immune system. J Investig Med. 2011;59(6):881-886. doi:10.2310/JIM.0b013e31821b8755 
  2. Forrest KY, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutr Res. 2011;31(1):48-54. doi:10.1016/j.nutres.2010.12.001 

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