Recent studies at several major universities including Penn State, Boston University, Harvard Medical, and Northwestern hold promise as early findings indicate a direct correlation between serum levels of vitamin D in participants and the COVID-19 virus.[4] 

Nationwide, many clinical trials to test the efficacy of vitamin D supplementation and its ability to reduce the risk of hospitalization (or fatality) from COVID infection are currently underway.  Several major university studies have already concluded, finding positive correlations between the “sunshine” vitamin and lower rates of infection or serious complications from coronavirus.[14]

In fact, in one major published study conducted by BUMC (Boston University Medical Campus) doctors found that of patients over 40, where vitamin D levels are within normal ranges, patients were 51.5% less likely to die from COVID-19 than those with blood levels of 25-hydroxyvitamin D less than 30 ng/mL.[4]

Further, it was found that sufficient levels of vitamin D could reduce the contraction of COVID-19 by 54% as well as other upper respiratory infections caused by influenza.[4]

Vitamin D, Mass Distribution

While not yet administered on a national level in the U.S. some European countries have already begun distributing vitamin D to at-risk populations in efforts to utilize every available tool in the fight against COVID-19.  Many seniors and board and care residents will receive up to 400 IU or 10 micrograms of vitamin D for a period of 4 months this winter in hopes of slowing the spread of coronavirus and its serious outcomes.[3]

The Power of Vitamin D 

According to research the primary mechanism at play in severe coronavirus cases involves inflammation.  Clinical outcomes including loss of consciousness and hypoxia (oxygen starvation) are greatly reduced in patients with sufficient vitamin D levels, as well as the inflammatory marker C-reactive protein.  Vitamin D therefore, likely plays a critical role in neutralizing many of the harmful symptoms associated with COVID-19.

Not Just for Coronavirus

Beyond the possible protection vitamin D can provide from the coronavirus infection and its severe symptoms, vitamin D may work to prevent the contraction of influenza A and/or lessen the length of recovery time significantly.  

In one clinical study doctors found that supplementation with vitamin D was not only an effective preventative for the flu, but also reduced secondary asthma in school age children.  Further, the winter seasonal drop in vitamin D due to limited exposure to sunlight correlates with the increase in influenza cases at this time.

By supplementing the diet with just 2000 IU of vitamin D, levels become normal in adults and seniors.

One physician’s group has even coined the term, “the vitamin D hammer” referring to a 1-time dose of 50, 000 IU’s or 10,000 IU’s of vitamin D, 2 to 3 times daily given to patients with the flu.  Results are dramatic, as patient symptoms generally resolve in 48 to 72 hours.  At a cost of only a penny per 1000 IU’s, some doctors are anxious to conduct further research on vitamin D supplementation and virus treatment outcomes.[11]

Inflammation is Key

Patients who suffer with severe COVID-19 symptoms generally get ill with 1 or more serious conditions including pneumonia, acute respiratory distress syndrome (ARDS), myocarditis or microvascular thrombosis brought about by a “cytokine storm”.[16]  

The Cytokine Storm

The cytokine storm occurs when cytokines, or small proteins important for cell signaling trigger an immune system response when the body begins to attack its own tissue and cells in addition to the virus.  This cytokine storm is responsible for the inflammation that occurs in COVID-19 patients that can severely damage the lungs and cause the Acute Respiratory Disorder Syndrome (ARDS) that is sometimes fatal.[5] 

Vitamin D not only works to enhance the body’s own immune system, but helps control dangerously overactive cell activity that leads to serious even fatal complications from COVID-19.

These inflammatory conditions cause many of the COVID related deaths.

To avoid catostrophic injury to the lungs and other organs it is critical to reduce the amount of inflammation early on.  This gives the body the best chance at acquiring possible immunity aqainst COVID-19.

T regulatory lymphocytes or (Treg) cells help the body fight against viral infection.  In severe COVID-19 cases, patient Treg levels are often low.  Conversely, higher blood levels of T regulatory lymphocytes are associated with lower incidence of respiratory viral disease.[5]  

Vitamin D supplementation has been found to raise Treg levels.  

How widespread is vitamin D deficiency?

Vitamin D deficiency is common in 30-60% of western, southern, and eastern European nations.  Up to 80% of middle-eastern populations are vitamin D deficient as well.[12]  

Vitamin D deficiency is also implicated in patients with obesity and diabetes.  These patients are at higher risk of death from COVID-19 than those without these conditions. 

Prevalence of Vitamin D Deficiency in Americans

In the American population, 35% of adults are Vitamin D deficient.  This number is much higher (about 50-60%) among the elderly and hospitalized.[12] 

Some at-risk populations for Vitamin D deficiency include:

• African Americans
• Hispanics
• Individuals who are obese
• Those with malabsorption syndrome
• Individuals who take certain medications[12]

Why are older adults at-risk for vitamin D deficiency?

Seniors suffer with insufficient vitamin D because their skin exposure to adequate sunlight is generally reduced.  In many cases older adults require dietary supplementation to reach sufficient levels of the vitamin.[6]

Between the ages of 20-80 vitamin D syntheses in the skin declines by 50%. 

COVID-19 in patients over 60 has been linked to insufficient stores of vitamin D.[2] 

Levels of Deficiency

Vitamin D deficiency is recognized as mild, moderate, or severe based on varied serum levels:

Mild deficiency: 25-hydroxyvitamin D less than 20 ng/mL

Moderate deficiency: 25-hydroxyvitamin D less than 10 ng/mL

Severe deficiency: 25-hydroxyvitamin D less than 5 ng/mL[15]

Identifying Vitamin D Deficiency

A blood test known as the 25-hydroxy Vitamin D blood test

 is required to accurately diagnose Vitamin D deficiency.  After receiving supplementation over a period of time, individuals should be retested to determine new levels and whether a deficiency still exists.[15]

Vitamin D deficiency is defined as a 25(OH)D of less than 0.8 IU. Vitamin D insufficiency has been defined as a 25(OH)D of 21–29 ng/mL[8]

The Recommended Dietary Allowance (RDA) of Vitamin D for all age groups is:

200 IU for adults younger than age 51  

400 IU for 51 to 70-year-olds  

600 IU for individuals over 70

Some experts recommend 800 to 1,000 IU/day

Vitamin D taken up to 2,000 IU a day is considered safe.[13]

Many Americans suffer from Vitamin D deficiency because they are not exposed to enough sunlight and sufficient levels cannot be reached through natural diet alone.  With greater exposure to sunlight in the summer months, vitamin D stores naturally increase and fewer cases of viral contagion exist. 

Natural Vitamin D

Vitamin D is the only one of 13 essential vitamins that can be produced within the human body.  This occurs when ultraviolet light reacts to a specific cholesterol on the skin creating what is known as D3.  When D3 travels through the liver and kidneys it is converted to vitamin D, the usable form of the vitamin.  We also take in small amounts of vitamin D from certain foods including oily fish such as salmon, mackerel, and sardines and from eggs and red meats.[9]

D2 and D3—What’s the difference?

Vitamin D is crucial for healthy bone growth as it facilitates the absorption of calcium.  Critical for immune function as well as muscle and skin health, vitamin D also helps the body control inflammation caused by viral infections such as COVID-19. 

While exposure to sunlight helps the body create about 90% of its needed vitamin D, 10% comes through fortified diet and supplements.[1]  The two main important forms of vitamin D are D3 and D2.  When sun exposure is limited greater supplementation may be necessary.  D3 also referred to as cholecalciferol is sourced from animals while D2 comes from plants (ergocalcifero).  D3 supplementation is recommended over D2.  Both are synthesized in the body.[10]

Should I take Vitamin D?

Supplementing the body with vitamin D is only necessary when there is a verified deficiency.  In the event there is no deficiency additional vitamin D is not effective for the prevention or severity of any viral infection.[7] 

How much vitamin D should I take as a supplement? 

If you are vitamin D deficient a healthcare provider or registered dietician may recommend the following dosage of vitamin D3.  This varies however, depending on the level of deficiency and any underlying risk factors. 

If you are deficient:

Adult Initial Dose

8 weeks initial vitamin D supplementation 6,000 IU per day or 50,000 IU once weekly

Adult Maintenance Dose

This may include 1,000 to 2,000 IU daily once serum 25-hydroxyvitamin D levels go over 30 ng/mL

Supplementation with high doses of vitamin D3 (up to 10,000 IU/day) may be necessary for some individuals.

Children with vitamin D deficiency may require 2000 IU daily or up to 50,000 IU once weekly for 6 weeks to reach maintenance levels of vitamin D3.  

Once children reach appropriate levels of vitamin D3 they can then move to a maintenance dosage of 1000 IU daily.[12]

Vitamin D Consumption

While some foods naturally contain vitamin D, product fortification and consumable supplementation is usually needed to help meet the recommended daily requirement for the vitamin.

What foods can I eat that contain vitamin D?

Some foods naturally contain vitamin D while others are fortified to increase the nutritive value.

Foods that naturally contain vitamin D include:

Fatty fish such as trout, salmon, tuna, and mackerel. 

Beef liver, cheese, mushrooms and egg yolks also contain small amounts of vitamin D

Most food-based vitamin D comes from fortification.

Commonly fortified foods include:

Cereal, orange juice, margarine, yogurt, soymilk, and almond milk[9]

As we continue the fight against COVID-19, it is critical to arm ourselves with every possible tool and treatment available including vitamin D supplementation if necessary.