Vitamin D and Immune Health

Low levels of vitamin D in the blood (25-hydroxyvitamin D) are associated with higher risks of acute upper and lower respiratory tract infections such as flu, according to a systematic review based on 39 human epidemiological studies. (1)

During late winter and early spring, solar radiation is weak and the vitamin D synthesis via our skin is at its lowest. As a result, our serum vitamin D levels are much lower compared to during summer. (2) It is especially important to supplement vitamin D via diet and supplement during this time.

Vitamin D is a very important nutrient for our immune system. (3) For example, vitamin D stimulates the expression of anti-microbial peptides in immune cells and in epithelial cells lining the respiratory tract. These peptides help protect the lung from infection. (4)

Pooled data from 25 randomized controlled trials involving nearly 11,000 subjects found vitamin D supplementation reduced the risk of acute respiratory tract infection. The protective effects were more evident in those who received vitamin D regularly and those who had low serum vitamin D at baseline. (5)

Maintaining healthy vitamin D levels helps support immune function in the long term.

However, please note there are no studies investigating the effect of vitamin D on the immune response to the novel coronavirus. There is no clinical evidence showing vitamin D helps prevent, reduce, or treat COVID-19 infection.


  • Jolliffe DA et al. J Steroid Biochem Mol Biol. 2013;136:321-329.
  • Barger-Lux MJ et al. J Clin Endocrinol Metab. 2002;87(11):4952- 4956.
  • Baeke F et al. Curr Opin Pharmacol. 2010;10(4):482-496.
  • Cannell JJ et al. Epidemiol Infect. 2006;134(6):1129-1140.
  • Martineau AR et al. BMJ. 2017;356:i6583.

Lewis Chang, Ph.D. is the Scientific Editorial Manager of R&D at Metagenics. Dr. Chang received his Ph.D. in Nutritional Sciences at the University of Washington, along with his MS in Nutrition and Public Health from Teachers College, Columbia University, and BS in Pharmacy from National Taiwan University. Prior to joining Metagenics, he conducted dissertation research and completed a research assistantship and postdoctoral fellowship at the Fred Hutchinson Cancer Research Center in Seattle, WA. Dr. Chang has authored or co-authored and managed the publication of over 30 peer-reviewed journal articles and numerous scientific abstracts and posters. He has quite a green thumb, enjoys opera, theater, and jazz, and loves cooking, collecting art, and learning to play gypsy jazz guitar.

Directions: Take daily or as directed by your healthcare practitioner. Do not exceed the recommended dosage unless directed by your healthcare practitioner.

This product is non-GMO and gluten-free.

Caution: If pregnant or nursing, taking other nutritional supplements or medications, or if taking anticoagulants, consult your healthcare practitioner before use.

Warning: If pregnant or nursing, taking other nutritional supplements or medications, or if taking anticoagulants, consult your healthcare provider before use. Keep out of the reach of children.

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I continue to research ways to boost our immune system, something I have done for many years. This article by Lewis Chang, Ph.D. from Metagenics, below, explains why Vitamin D is so important. Especially now. Please do not overdo Vitamin D. (see cautions and warnings below. Consult your Physician) I take slightly less than recommended unless I can be tested with blood work for Vitamin D levels.I have two links for Vitamin D products I like, one in liquid form which I take, another in a capsule with Vitamin K added, and is high potency. Please do not take overdo Vitamin D.These links go directly to the Shape-Up Metagenics site. You receive 20% off the listed price and free shipping on all Metagenics products you order through the site.

  • D3 Liquid Designed for Enhanced Absorption $26.95 – 20% = $21.56
  • D3 10,000 + K $27.95 -20% = $23.36 – High Potency, Bioactive Vitamin D with Vitamin K D3 10,000 + K . D3 10,000 with K2 provides 10,000 IU per softgel of vitamin D (as D3), designed for greater absorption. This high potency formula also includes bioavailable forms of vitamin K2 to complement vitamin D.
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