Vitamin D Deficiency And COVID-19: Is There A Connection? 

As we are well into the second wave of COVID-19 infections, it is clear that the SARS-CoV-2 virus is going to be around for a while. As we use Functional Medicine approaches, we not only want effective strategies for treating active infections, but we also want to create resiliency in the host.

A resilient immune system is the most effective defense that you have. 

Vitamin D is a fascinating nutrient and one that I think about clinically with most of my patients. It’s been so exciting to follow the emergence of vitamin D research and how our knowledge has evolved which has all happened during my time as a practicing physician. 

Vitamin D is part vitamin and part hormone and it influences every cell in the body. We’ve known about vitamin D’s role in immunity for a long time, and now we know more about its benefits with COVID-19. I’m going to share this exciting topic with you in today’s article. 

In this article, you will learn more about: 

  • The important role vitamin D plays in the immune system 
  • The definition of vitamin D deficiency and the reasons behind it
  • What the research says about vitamin D and respiratory infections, including COVID-19
  • How to optimize your own vitamin D levels using high quality supplements

Let’s get started!

Vitamin D and Immunity 

Vitamin D is an essential fat-soluble nutrient, synthesized from cholesterol when sunlight hits the skin, or obtained through food, and plays a role similar to a hormone in the body. 25-hydroxy vitamin D is the form that we typically test for in the blood, which is activated by the liver and kidney into 1,25-dihydroxy vitamin D, the active form. 

Every cell in the body has receptors for this active vitamin D and when it binds to the cell, it regulates the expression of genes. This is just one way that our environment helps to determine gene expression and our epigenetics

We typically think of vitamin D in terms of bone health. A major role of vitamin D is to help with the absorption of calcium from the diet. Without enough vitamin D, children develop rickets and adults can develop osteomalacia, or softening of the bones. 

However, vitamin D also has plays many other roles in the body, one of which is its importance for immune health. Vitamin D is considered an immune system modulator where it: 

  • Reduces inflammatory messengers, called cytokines
  • Increases immune cell function, particularly of macrophages
  • Increases the antimicrobial actions of immune and other cells

The result is that vitamin D stimulates immune defenses, but also keeps the immune system in check so it doesn’t become overactive. This is one reason that strong vitamin D levels help to manage and even to prevent autoimmune disease

Vitamin D Deficiency 

Vitamin D deficiency is a widespread problem in the United States and globally. Deficiency is defined as blood levels below 30 nmol/L. I routinely test vitamin D levels in my patients and am always surprised by the low values I see, even here in sunny Austin, TX. 

The two main reasons that vitamin D deficiency is so prevalent are:

1. There are few natural dietary sources of vitamin D, including fatty fish and liver, and many people either don’t have access to these foods or don’t eat a diet that includes them. 

2. We aren’t being exposed to enough sunlight to produce adequate amounts of vitamin D, because of geographic location, seasonality, spending more time indoors, the use of sunscreen and cover ups when outdoors and other social factors. 

It’s no wonder vitamin D deficiency is epidemic – our modern lifestyles don’t support adequate intake or exposure. I’ll talk about raising levels towards the end of this article, but first let’s look at how vitamin D deficiency relates to COVID-19. 

Vitamin D and COVID-19

More frequently I’m being asked: does vitamin D protect against COVID-19?

Having strong vitamin D levels doesn’t prevent you from contracting the virus, this is where hand washing, wearing masks and distancing is helpful, but it may reduce the complications and even prevent death from COVID-19. 

Let’s take a look at some of the research. 

It’s been previously established that low vitamin D increases the risk of respiratory infections, including ARDS (acute respiratory distress syndrome), while vitamin D supplementation helps to reduce the risk of such infections. One of the roles of vitamin D in the immune system, as I explained above, is to increase anti-microbial peptides in cells, and this includes the epithelial cells that line the respiratory tract. 

In one randomized controlled trial of elderly people in long-term care, monthly high dose vitamin D supplementation was shown to reduce the incidence of upper respiratory infections, URIs, in the center’s residence. 

This is all great news since COVID-19 affects the immune system and respiratory system. The research specifically on SARS-CoV-2, the virus that causes COVID-19, is beginning to paint a similar picture. 

One study looked at vitamin D levels of COVID-19 patients in Spain, Italy and Switzerland and found low vitamin D levels correlate with more COVID-19 cases, more complications and higher mortality rates. The study also noted that vitamin D levels are lower in the aging population and these tend to be the people most vulnerable to COVID-19 severity and death. 

In another article looking at the population in Switzerland, low vitamin D levels were associated with positive SARS-CoV-2 tests where those with negative tests were more likely to have higher vitamin D levels. 

A recent review article raises some interesting points, showing that infection rates are lower in the Southern Hemisphere as the infection hit at the end of summer when vitamin D levels tend to be higher versus in the Northern Hemisphere where the pandemic spread at the end of winter when vitamin D levels are at their lowest. They also cite evidence that vitamin D reduces the risk of influenza. 

Another article looked at the links between COVID-19, Parkinson’s disease and vitamin D, concluding that vitamin D has the potential to both slow the progression of Parkinson’s while offering protection from COVID-19. 

Taken together, this evidence for vitamin D reducing the symptoms and severity of respiratory infections and possibly COVID-19 makes it an important tool in our prevention toolkit. It’s important to note many scientists admit that more research is needed to make a clear connection with vitamin D’s role in COVID-19, but because vitamin D is safe and has so many other health benefits, optimizing vitamin D levels is a key part in overall preventative medicine. And one definitely worth focusing on.

Optimizing Vitamin D Levels

As a Functional Medicine physician, when it comes to vitamin D, I’m not only looking at preventing deficiency, but also invested in optimizing levels. While a blood level of 30 nmol/L of might be sufficient to prevent rickets or osteomalacia, it doesn’t optimize the levels required for immune health. 

The Institute for Functional medicine recommends blood levels between 50 and 80 nmol/L to help mitigate morbidity and mortality from COVID-19. 

I always recommend getting your levels tested and then adjusting supplementation to achieve your vitamin D goal. If you don’t have recent labs, taking 5000IU per day is a reasonable, and safe, amount. 

One paper even suggests taking 10,000 IU per day for several weeks with a known COVID-19 infection, in order to rapidly raise levels, but I would recommend knowing your blood levels before going this high or talking with your doctor about it. 

It’s important to note that these dosages are much higher than the recommended daily intake of 600IU per day, which tends to be too low to optimize blood levels. 

Vitamin D is a fat-soluble nutrient and is best taken with food. I also recommend taking vitamin D supplements early in the day where the timing will mimic exposure to natural sunlight. 

You have several options for supplementation and vitamin D can be taken as a capsule or liquid. It’s often combined with vitamin K2 to offer additional bone support. 

Since nutrients don’t act alone in the body, and we have evidence for other nutrients and botanicals offering COVID support, I’ve put together this Immune Protect Bundle that combines vitamin D, with vitamin C, zinc, IgG immune support, anti-vital herbs and quercetin. This is a great place to start if you are looking for comprehensive immune support in light of COVID-19.

Let’s not forget the role that food and sunlight play when optimizing vitamin D levels. For some people in some locations, lifestyle factors might be enough to maintain healthy blood levels, but I find that most people benefit from a maintenance supplemental dose once achieving optimal levels. 

When we understand why vitamin D deficiency occurs – either from lack of high vitamin D foods, lack of sunlight exposure, or both – it is clear to see the factors that will help to support healthy levels. Here are a couple tips:

1.Increase fatty fish and liver in the diet. These foods also contain vitamin A and other nutrients that act synergistically in the body with vitamin D. Shoot for 3 servings of low mercury fish per week along 1-2 ounces of pastured chicken or grass-fed beef liver. High quality liver is also available in capsules for convenience. If you need some inspiration to get started, try my Salmon Lettuce Wraps, Almond Flour Crusted Sardines or Salmon Salad with Paleo Ranch.  

2. Increase sun exposure. During the summer months, aim for exposing your arms and legs to peak sun (between 10am and 2pm) without sunscreen most days. The time will depend on your skin tone and sensitivity to sunlight. You don’t want to burn, but you want to generate some vitamin D. Somewhere between 10 and 30 minutes is a good range to experiment with. 

Since it is clear that COVID-19 isn’t going away anytime soon, this is the perfect opportunity to raise vitamin D levels into that optimal range. This will help support your immune system as we enter the colder and darker months of the year.

Get your sunshine, salmon and supplements today for stronger defenses tomorrow!


UPDATE- More research on Vitamin D – Effect of Vitamin D3 Supplements on Development of Advanced Cancer: A Secondary Analysis of the VITAL Randomized Clinical Trial.


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