Why Vitamin D is on the Back-to-School List

Usually “Back-to-School” is the LAST thing on my mind in July. I love summer and prefer to indulge my senses in the moment: juicy tomatoes, tart cherries, hot orange nasturtiums, long sunny days with dips in the pond and late suppers on the porch… ahhh…. 

Man in mask holding back-to-school sign.

But this year, as we all know, things are different. I cannot stop picturing a classroom of children, masked, sitting at desks carefully spaced 6 feet apart, trying to adjust, along with their teachers, to a new learning environment. 

Kids need to get back to school, and it looks like COVID-19 infections are here to stay, at least for now, so my thoughts have turned towards preparation. My child’s school is hard at work creating a safer environment – even providing outdoor classrooms and hybrid online/in-person learning options. 

But there is more we can do, starting now at home, if we focus on supporting innate immunity. External masks provide a barrier to infection, but they are not foolproof, especially in rambunctious children. If contagious particles manage to thwart the mask, we rely on defenses within us that can make or break the trajectory of infection.

These defenses constitute our innate immunity:

  • Physical barriers – skin, the GI tract, respiratory tract, eyelashes, and body hair
  • Defense mechanisms – secretions, mucous, gastric acid, saliva, tears, and sweat
  • Generalized immune responses – inflammation, complement, and non-specific cellular responses
  • A host of white blood cells with specific roles such as monocytes, macrophages, antigen presenting cells, natural killer cells, and neutrophils  

There are many ways to support innate immunity in children and adults, including elders, who are at particular risk during this pandemic. One of the simplest, and most affordable is to ensure healthy levels of vitamin D. 

Vitamin D supplements.

The role of vitamin D in immune function, particularly for respiratory infection has been studied for years. Vitamin D has been shown to have a balancing effect on immunity and to be protective against respiratory infections, including influenza. 

As author and medical herbalist, Paul Bergner, points out in his article, Vitamin D, COVID-19 and Cytokine Storm: a 2010 clinical trial demonstrated a 42% reduction in the incidence of influenza A in school children receiving a vitamin D supplement, and an 83% reduction in asthma attacks (Urashima, et al). This may be partly due to the production of antimicrobial peptides supported by the action of vitamin D. 

An article by J.J. Cannell, et al, found that “activated vitamin D… has profound effects on human immunity… (and) acts as an immune system modulator, preventing excessive expression of inflammatory cytokines and increasing the ‘oxidative burst’ potential of macrophages.” The article states further, “It dramatically stimulates the expression of potent anti-microbial peptides, which exist in neutrophils, monocytes, natural killer cells, and in epithelial cells lining the respiratory tract where they play a major role in protecting the lung from infection…. Vitamin D deficiency predisposes children to respiratory infections. Ultraviolet radiation (either from artificial sources or from sunlight) reduces the incidence of viral respiratory infections, as does cod liver oil (which contains vitamin D). An interventional study showed that vitamin D reduces the incidence of respiratory infections in children.”

An article in The Lancet, Vitamin D and COVID-19: do the deficient risk a poorer outcome?, points to a 2017 meta-analysis of data from 11,321 participants in 25 randomized controlled trials that showed “vitamin D supplementation protected against acute respiratory tract infections and that patients with very low (<25 nmol/L) serum 25-hydroxyvitamin D concentrations (a marker of vitamin D status) gained the most benefit.” 

The Lancet article proposes two key roles vitamin D might play in the body’s defense mechanism against COVID-19: 

  1. Vitamin D supports production of antimicrobial peptides in the respiratory epithelium, thus making infection with the virus and development of COVID-19 symptoms less likely.
  2. Vitamin D might reduce the inflammatory cascade associated with SARS-CoV-2. It is known to interact with ACE2 and promote its expression as an anti-inflammatory and cardiovascular regulator.

Dr. Rose Anne Kenny, lead investigator of the Irish Longitudinal Study on Ageing (TILDA) and co-author of Vitamin D deficiency in Ireland – implications for COVID-19 is “adamant that all public health bodies should be for the population to take vitamin D supplements during this pandemic.” She states, “The circumstantial evidence is very strong,” and that due to the high safety of vitamin D supplementation, and widespread wintertime deficiency in northern latitudes, it makes sense to make vitamin D supplementation, especially among elders, a standard of care.

BIPOC in the sun.

It is also important to note that supporting healthy vitamin D levels in People of Color is especially important. Melanin blocks the production of vitamin D from sun exposure and the risk of mortality has been found to be as much as 4 times greater among Blacks in the U.K. than white folks. In the U.S., addressing disparity of health care for Black, Indigenous, and People of Color is of greatest importance to reduce this elevated risk of mortality.

A Few Key Notes on Vitamin D:

  • What is vitamin D? Vitamin D is a fat-soluble vitamin/hormone essential for bone and muscle health. It may have immune benefits and protect against respiratory viral infection and cytokine storm. Learn more here.
  • How do we get enough vitamin D? In northern latitudes, 10-20 minutes of mid-day sun exposure, April – October, will trigger the synthesis of vitamin D3 in the skin. Some food sources such as fatty fish and fortified dairy products contain vitamin D3. D3 supplements are also available.
  • How do I know if I am vitamin D deficient? The only way to know for sure is to take a blood test for 25-hydroxyvitamin D (25-OH vitamin D). Less than 30 ng/mL is considered deficient by most labs; however, some healthcare practitioners suggest a target level of 40-60 ng/mL.
  • Is it safe to take vitamin D supplements? Daily doses of 400 iu to 5,000 iu appear to be extremely safe for children, adults, and elders. Always consult with a healthcare practitioner regarding your unique health concerns. Remember that regular testing is important and will help guide you to an appropriate daily regimen.
Eating the sun.
(U.S. Air Force photo by Senior Airman Jensen Stidham)
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