Vitamin D: A Big Superstar in Fighting Viral Infections

In recent years, vitamin D has become an increasingly popular supplement and for good reason. This critical micronutrient promotes the absorption of calcium to keep your bones healthy and also supports cardiovascular health. Vitamin D has several other roles in the body including modulating inflammation and cell growth. Exciting new evidence is showing another benefit of this vitamin – supporting a healthy immune system.  

A 2015 study1 examined the impact of vitamin D in supporting the immune response to infections such as the influenza virus. Researchers also studied the preventive and therapeutic potential of vitamin D in viral infections. This study found evidence to suggest that vitamin D plays a significant role in the complex immune response.  

A 2017 study2 assessed the impact of vitamin D supplementation on risk of acute respiratory tract infection. The study found that vitamin D was not only safe, but it was able to protect against acute respiratory infection. The patients who received the most benefit from adding vitamin D to their daily regimen were those who were very vitamin D deficient prior to beginning the study. The results showed that those who regularly supplemented their diet with vitamin D were even more protected.  

Despite the importance of this critical vitamin, over 40% of adults in the United States are vitamin D deficient. A few signs of a vitamin D deficiency are getting sick often, chronic fatigue, joint pain, mood changes, or bone and hair loss. Some foods are vitamin D fortified, but another source of dietary vitamin D is wild-caught fatty fish such as salmon or tuna. 


  1. Martineau AR, Jolliffe DA, Hooper RL, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017;356:i Published 2017 Feb 15. doi:10.1136/bmj.i6583
  2. Gruber-Bzura Vitamin D and Influenza-Prevention or Therapy? Int J Mol Sci. 2018;19(8):2419. Published 2018 Aug 16. doi:10.3390/ijms19082419