Can vitamin D help combat infectious diseases like COVID-19?

Can vitamin D help combat infectious diseases like COVID-19?

Most people know how important vitamin D is to maintain good bone health, but less well known is how it improves immune health. 
Until recently that is, when a study was published about hospital patients with COVID-19 were treated with a special form of vitamin D (calcifediol, which is how vitamin D looks like once it is converted in the liver, which may take up to a week).
The difference in outcome was quite remarkable: there was only one casualty among patients that were treated and far fewer had to be transferred to intensive care. Since then there's been a vastly increased interest for vitamin D supplementation.
We decided to dig a little further and found compelling evidence for its efficacy. Actually the evidence has been around for several years already, but was slow to trickle down to the general public (or physicians). 
As the coronavirus pandemic continues, many people are wondering how to keep themselves healthy. You know that social distancing, working from home and staying inside in general is one way to protect yourself, but are there other measures you can take?
Boosting your immune system is one of the best things you can do because it is your body's key defense when it comes to fighting a virus. Even if you are exposed to a virus, the coronavirus COVID-19 or others, if your immune system is strong, you have a better chance of not getting sick. 
Vitamin C is a popular choice for supporting immunity, but another key nutrient for your immune system is vitamin D. 
It turns out that vitamin D, is every bit as important as its vitamin C or other antioxidants whenever the immune system is under attack, like during a cold or flu.
Here’s how this underestimated vitamin can help boost immunity and fight viral infections.

The basics of vitamin D

First, it’s important to understand that vitamin D isn’t a “vitamin” at all, but rather a prohormone that is synthesized in response to interaction between cholesterol, the skin, and sun exposure.
Vitamin D is widely studied for all kinds of health benefits, like bone health, calcium absorption, heart health, and immunity. While experts differ on how much vitamin D is needed to provide protection and avoid symptoms of insufficiency or deficiency, nearly everyone agrees that you can’t get enough vitamin D from food alone.

Why you need vitamin D to boost immunity

When you take vitamin D, you lower your chances of getting sick from viral infections, like colds and the flu, by at least 10%. But people who are deficient in vitamin D actually see a greater protective benefit when they supplement, reducing their risk by 50%. 
Most people get far less than the recommended daily allowance for vitamin D of 600 IU, setting the stage for rampant deficiencies. Certain people, like those with Crohn’s disease, celiac disease, osteoporosis, or women who are pregnant or breastfeeding, have an even higher risk of being deficient because of issues with absorption in the intestines and because of greater demands.
Cold and flu viruses are contagious respiratory infections that affect the nose, throat, and lungs with symptoms like congestion, coughing, wheezing, sore throat, body aches, and fever. 
The flu, in particular, can have serious consequences in people who are at risk: the elderly, infants, young children, people with suppressed immunity, and those with other chronic disorders. On any given year, approximately 10 % of the population gets the flu, but during epidemic flu seasons, it can be as high as 20%. 
There are several overlapping factors that are associated to both the severity of the flu and being at risk of vitamin D deficiency, including:
- age (under age 2 or over age 65)
- pregnancy
- chronic disease (diabetes, heart disease, autoimmunity, etc.)
- suppressed immunity (HIV, chemotherapy)

Vitamin D reduces risk of the flu

While flu vaccines are common, they only address a few strains based on the best guesses by experts of which strains will predominate. Sometimes experts guess wrong, rendering the flu vaccine less effective during those seasons. What doesn’t change, however, is the immune system’s reliance on vitamin D levels, making it a more secure way to boost immunity and avoid the flu. Research even shows that optimal vitamin D levels boost the effectiveness of the flu vaccine.
One study even drew a direct link between vitamin D levels and the risk of getting the flu: Those with the lowest serum concentrations had the highest chances of getting viral infections.
Receptors for vitamin D are located on cell surfaces in the immune system, allowing vitamin D to bind to them. When this happens, vitamin D reduces inflammatory cytokines that perpetuate illness. 
Vitamin D also boosts the proteins that fight bacteria and viruses, which are essentially the natural versions of antibiotics that protect the body from infection.
Vitamin D boosts the innate branch of the immune system (the body’s first line of defense against infection) which mounts an attack against foreign invaders. The response time for this branch of the immune system is strongly associated with our ability to ward off illness or shorten the duration of sickness. When vitamin D levels are low, immune cells respond slower and the innate immune response is not as rapid as it should be.
Even if you do get sick, increase your vitamin D levels immediately for faster recovery. When your levels are too low, your body will struggle longer to bounce back.
Research shows that for every 4 ng/mL (or 10 nmol/L) increase in your vitamin D concentrations in the blood, you lower your odds of getting the flu by 7%. It’s not coincidental that flu season peaks as our natural ability to produce vitamin D falls due to reduced sun exposure in the colder months.

Cytokine storm

Vitamin D deficiency is known to enhance a process known as the “cytokine storm”.
Cytokines are proteins that are an integral part of the immune system. They can have both pro-inflammatory and anti-inflammatory effects and play important roles, helping protect against infection and disease.
However, cytokines can also induce tissue damage under certain circumstances.
A cytokine storm refers to the uncontrolled release of pro-inflammatory cytokines that takes place in response to infection or other factors. This dysregulated and excessive release of cytokines leads to severe tissue damage and enhances disease progression and severity.
In fact, it’s a major cause of multiple organ failure and acute respiratory distress syndrome (ARDS), as well as an important factor in the progression and severity of COVID-19.
For example, patients with severe cases of COVID-19 have been shown to release large numbers of cytokines. Vitamin D deficiency has been associated with reduced immune function and may enhance the cytokine storm.
As such, researchers postulate that a vitamin D deficiency may increase the risk of severe COVID-19 complications, as well as that vitamin D supplementation may reduce complications related to cytokine storms and uncontrolled inflammation in people with COVID-19.
Currently, multiple clinical trials are investigating the effects of vitamin D supplementation (at dosages up to 200.000 IU) in people with COVID-19.
Although research in this area is ongoing, it’s important to understand that taking supplemental vitamin D alone can’t directly protect you from contracting COVID-19.
However, being deficient in vitamin D may increase your susceptibility to overall infection and disease by harming immune function.

How to supplement with vitamin D

If you cannot get sun exposure regularly as most people do between early atumn until early spring (and ironically also for people in Spain, France or Italy during the most severe phase of lockdown) , then supplementation is essential to maintain steady levels. Vitamin D3 is considered to be the natural form and is most effective at raising serum concentrations. 
Dosage recommendations range from 400 IU to upwards of 10.000 IU, depending on health conditions and other factors, like absorption.
The best bet when it comes to supplementing with vitamin D is to have your doctor test your levels, because the dose you need depends on the vitamin D level you are trying to achieve.
Because vitamin D is a fat-soluble nutrient (meaning your body has limited ability to excrete it) , levels can become toxic in the body with over-supplementation, so get your blood levels checked before supplementing. 
vitamin D status ng/ml nmol/L
severely deficient 0-10  0-25
deficient  11-20  26-50
insufficient  21-32  51-81
adequate  33-49  82-124
optimum  50-65  125-163
high, but not toxic  66-100  164-250
toxicity possible  above 100  above 250
The optimum range is where vitamin D most effectively promotes good health and fights disease.
For most people the amount needed to get their vitamin D status in the optimum range (50-65ng/ml, 125-163nmol/l), follows this formula : vitamin D dosage = body weight (kg) * 60 .
This is the amount needed without any help from sunlight in autumn and winter, when we cover up our skin anyway against the cold.  
In summer we need less , the rule of thumb is that if 50% of your skin is exposed, you cover 100% of the amount of vitamin D you need, which is achieved when you expose your entire arms and legs to the sun (wear a sleeveless t-shirt and shorts)
Vitamin D supplements absorb best when paired with fish oil or fatty foods to optimize absorption. Magnesium also assists in absorption. 
Furthermore it is 
advised to combine vitamin D with vitamin K to prevent calcium deposit in the blood stream. 


Vitamin D is a critical nutrient for immune support. When the body is low in this nutrient, immune system cells will have slower response times to viral invaders, sickness duration will be longer, and overall immunity will be suppressed.
Vitamin D is one of the few nutrients that doesn’t have an abundance of food sources. We were designed to produce most of the vitamin D we need in the skin from sun exposure. But between food and supplements, as well as sun exposure in the warmer months, we can optimize our vitamin D levels for overall health.
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