The Benefits Of Vitamin D - what’s the research saying?

Vitamin D has many benefits for the skin, including the prevention of premature aging + acne. Vitamin D is also helpful in treating dry skin, psoriasis and eczema. But did you know that Vitamin D is extremely important for a healthy immune system? Read on and find out "what the research is saying" about Vitamin D.


Article written by Dr Michelle Gaucher

Originally posted at

Vitamin D for a strong immune system. Naturopath Victoria BC

This information is EXTREMELY important right now, as vitamin D seems to have never been as important as it is right now. I mean, it’s always been essential, but it currently has the spotlight for many reasons. There is so much talk about vitamin D and its effects on the immune system and how essential it appears to be to have optimal levels to help with COVID -19 outcomes. There have been multiple reports on how vitamin D deficiency is linked to more severe viral cases and mortality.

Living in a northern climate is one of the greatest risk factors for vitamin D deficiency. Humans in cooler climates do not synthesize vitamin D from sunlight (UVB rays) for approximately 6 months of the year (October to April). Furthermore, it is extremely difficult to get adequate vitamin D through dietary sources. The recommended daily allowance (RDA) for vitamin D according to the National Institute of Health (NIH) for adults 18-70 years of age is 600 IU per day. I would very much argue that this is far too low, especially in deficient climates. Over the last few months, I’ve tested more and more of my patients for vitamin D levels. The vast majority are moderately to severely vitamin D deficient (yikes!). Now, more than ever, this is a REALLY big deal and must be corrected. I find that checking serum levels of vitamin D (25-OH-vitamin D) is incredibly helpful in guiding treatment so that appropriate dosing can be safely & effectively followed for each individual.

Risk factors for vitamin D deficiency include:

  • Living in a cooler climate (further from the equator)

  • Less exposure to sunlight

  • Wearing sunscreen every time you’re exposed to sunlight - this inhibits vitamin D synthesis in the skin

  • Darker skin

  • Older age

  • No (or insufficient) vitamin D supplementation

  • Kidney disease

  • Malabsorption

  • Genetic defects in the vitamin D receptor (VDR)

  • Taking drugs that interfere with vitamin D levels

What does vitamin D do for the immune system?

Well, it does a whole lot, but here is a synopsis on why it is useful in the immune response against viruses and bacteria.

  • Regulation of gene expression via entering the nucleus of cells and binding receptors. Some of the genes that vitamin D regulates include those for:

    • Beta defensins —> cleave viral membranes/capsids, destroying them.

    • Cathelicidins —> involved in activation of neutrophils, dendritic cells and macrophages. All of these immune cells are involved in the killing of viral and bacterial infections.

  • Enhances expression of lysosomal enzymes and nitric oxide release which help kill infectious pathogens.

  • Regulates the adaptive immune response by dampening T cell proliferation and maturation during viral respiratory infections. This shifts the Th1 response to a Th2, which in turn helps modulate the pro-inflammatory response (ultimately it reduces pro-inflammatory cytokine release). It will shift Th17 to T regulatory cells, leading to an increase in anti-inflammatory cytokines. This all makes it sound like it’s counterproductive to proper immune function and fighting infection, but it’s regulatory role seems to contribute to the inhibition of hyper-inflammation that would normally lead to complications (such as thromboembolism and tissue damage in the host).

  • Vitamin D deficiency also plays a very complex role in auto-immune conditions, highlighting how essential it is for proper immune function.

This vitamin influences the immune system in several ways, but these are some examples of it’s modulating effect. It has a dual effect in infection control. It inhibits the viral replication early on while also reducing the resultant hyper-inflammation that’s associated with severe complications.

So what’s the research telling us so far?

Well, I have good and bad news for you. I’ll hit you with the bad news first, it turns out there are a lot of individuals with inadequate vitamin D levels since many aren’t supplementing with adequate doses or at all. The good news is that vitamin D is an affordable supplement that is widely available and easy to take and bringing up your serum levels shows to be quite protective. Here is a summary of the research that has been done specifically with vitamin D and COVID:

  • There is a 64% increase in severe COVID-19 cases in those with vitamin D deficiency compared to mild cases.

  • Vitamin D insufficiency increased hospitalization (~6x increased risk) and mortality from COVID-19 (~15x greater risk).

  • Those older than 65 years of age are at a higher risk for vitamin D deficiency for many reasons (comorbidities, polypharmacy, reduced synthesis in skin, etc.) and this may be an important factor when considering severity of cases in the elderly population.

  • Serum levels of vitamin D are inversely related to pro-inflammatory cytokines (inflammatory mediators), and C-reactive protein (inflammatory marker), modulating the cytokine storm caused by COVID-19. Low vitamin D levels are also associated with an increased risk of cardiac insufficiency.

  • Higher serum vitamin D levels were found in individuals with significantly lower lung involvement in COVID-19 patients compared to patients with lower vitamin D levels.

  • Across 40 countries, vitamin D deficiency was shown to be >50%, especially among care home residents.

  • In general, adequate vitamin D levels have been shown to reduce the risk of acute respiratory tract infections. Although this has not been established for COVID-19 thus far, it is an interesting association to keep in mind. 

The Bottom Line:

  • Vitamin D deficiency is much more prevalent than previously thought and should be investigated more often in patients. The RDA value for vitamin D is generally too low.

  • Risk factors for vitamin D deficiency include reduced sun exposure, living in cooler climates (further from the equator), darker skin, lack of supplementation, older age, malabsorption, kidney disease, genetic mutations in the vitamin D receptor and taking drugs that interfere with vitamin D metabolism.

  • Vitamin D deficiency appears to be associated with a significantly greater risk of hospitalization and death from COVID-19. Although there are other factors involved in the severity of the infection, this association has been substantiated by numerous retrospective studies performed.

  • The dual effects of vitamin D on the immune system seem to make it quite effective in fighting viral infections. It directly kills viruses, inhibits their replication and also reduces the hyper-inflammation of the cytokine storm involved in severe complications of the infection.

  • Vitamin D dosing should be individualized depending on the person and their history and serum 25-OH-vitamin D levels. Consult a licensed naturopathic doctor to ensure your vitamin D levels are optimal and for safe & effective supplemental dosing.

  • Prioritizing optimal health is always essential and greatly reduces the risk of disease in general. Start making your health a priority now, because if not now, when?!

  • *Important*: Vitamin D supplementation is not a cure nor an approved treatment for COVID-19, you must still follow the local public health orders and recommendations.

If you are interested in evaluating your vitamin D status and optimizing your health, book an appointment with me! 


**Disclaimer: This information is for educational (and motivational) purposes only, it is not medical advice. Always consult a licensed naturopathic physician before starting any supplements or natural health products. Vitamin D supplementation is not a cure for COVID-19; local public health orders and recommendations should be followed.





PMID: 33146028

PMID: 32397511

doi: 10.2139/ssrn.3571484

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