Vitamin D, Coronavirus, and Your Immune System

Vitamin D is a fat soluble vitamin that is primarily obtained through sun exposure. It can also be present in some foods (many fortified with vitamin D) and through dietary supplementation. In the body, vitamin D must undergo a hydroxylation process to become activated. In the liver vitamin D is converted to 25-hydroxy vitamin D, also known as calcidiol. The kidneys then utilize calcidoil to form 1,25-dihydroxy vitamin D, or calcitriol. Vitamin D plays a huge roll in our bodies including the absorption of calcium through our gut, the mineralization of our bones, modulates cellular growth, and affects neuromuscular and immune function, as well as plays a roll in inflammation.

How To Tell If You Are Vitamin D Deficient

It is believed that most adults are somewhat vitamin D deficient. Individuals who live in northern regions where there is less sun exposure, those who are overweight and those with dark skin are more likely to be vitamin D deficient. Shift workers, health care workers, and indoor workers are also at an increased risk due to reduced sun exposure. Vitamin D is a fat soluble vitamin, meaning it is stored in body fat. Because of this, people who are overweight have a decreased ability to use the vitamin within the body. In addition, the amount of melanin you have in your skin, affects how much vitamin D your body can produce from sun exposure. The darker your skin, the more melanin you have in your body. Therefore, the fairer your skin, the more efficiently your body will be able to produce vitamin D. However, less melanin also comes with the risk of increased probability of skin cancer.

Dr Danielle and Vitamin D

Serum concentration levels of calcidiol are the way best way for your doctor to determine your vitamin D status. Even though there is much discussion on what healthly vitamin D levels should look like, according to the National Institutes of Health (NIH), vitamin D levels can be categorized in the following way (1):



Health Status



Vitamin D deficiency

30 to <50


Inadequate vitamin D levels






Potential adverse effects

* 1nmol/L =0.4ng/mL

** Serum concentrations of 25-hydroxy vitamin D, calcidiol, are reported in both nano moles per liter (nmol/L) and nanogram per mililiter (ng/mL).

Clinically, I like to see adult men between 50-70nmol/L and adult woman 60-80nmol/L.

Effects of Vitamin D Deficiency

Effects of vitamin D deficiency

Vitamin D deficiency not only increases the risk of rickets in children, but also increases risk of osteopenia, osteoporosis, and fractures in adults. Additionally, vitamin D deficiency is “associated with the increased risk of common cancers, autoimmune diseases, hypertension, and infectious diseases.” (2)

Vitamin D deficiency may also be be associated with the following health conditions (3)


Multiple Sclerosis

Candida overgrowth


Inflammation and swelling

Heart Disease

Weak or broken bones

Chronic pain

High blood Pressure

Immune issues or weakened immune system

Chronic fatigue

Hormone imbalance

Autoimmune diseases

Depression and anxiety








How Vitamin D Relates To the Immune System

Vitamin D plays a crucial role in having a good immune system, overall health and well-being, as well as a decreased disease incidence. Vitamin D can boost the immune system, help fight bacterial, fungal, and viral infections.

Vitamin D receptors are expressed on immune cells and vitamin D plays an important roll in our innate and adaptive immune responses. Our innate immune systems kick in immediately or within hours after an exposure to an antigen (a toxin or foreign substance). Our adaptive immune systems are also referred to as our acquired immune system, in which the body has an enhanced response to future encounters with that particular antigen.

Vitamin D and the immune system

Vitamin D deficiency has been linked to increased autoimmunity as well as susceptibility to infection. Multiple cross sectional studies have shown that lower levels of vitamin D are associated with increased infections as well as longer recovery times, in particular with upper respiratory tract infections and influenza. In addition to having numerous effects on cells within the immune system, vitamin D plays a roll in decreasing the production of inflammatory cytokines (IL-17, IL-21), increasing anti-inflammatory cytokines, such as IL-10, as well as inhibiting monocyte production of inflammatory cytokines (ex. IL-1, IL-6, IL-8, IL-12, and TNFα. Ultimately, cells of the immune system are capable of responding to vitamin D in a way that boosts the immune function in our bodies and as well as decreases inflammation. (4)

Coronavirus and What It Is Attacking

Many people are asking right now if taking vitamin D can prevent them from catching COVID-19. The truthful answer is that more research is needed, but growing evidence supports the theory that vitamin D deficiency may be a risk factor for those who contract COVID-19. Research is showing that vitamin D deficiency may also dictate how severe there reaction is to COVID-19. Vitamin D deficiency is more common in African-Americans and those of color, which may also help explain why these populations are experiencing a more severe reaction to the coronavirus. It is important to note that age as well as co-morbidity factors such as diabetes, heart disease, those who are immune compromised and those with cancer do have other factors at play that may be leading to more severe reactions to COVID-19.

Covid 19 and Vitamin D

Doctors are seeing many COVID-19 patients with an overreaction or hyper-inflammatory response of the immune system. This dangerous overreaction is often referred to in the medical community as a “cytokine storm”. While no definitive research can say vitamin D helps with this COVID-19 related hyper-inflammatory reaction, vitamin D in general has been found to decrease the immune system's inflammatory response, decrease the risk of contracting respiratory tract infections, as well as lessening the severity and duration of them. (5) A COVID-19 observational study found that “Serum 25(OH)D level was lowest in critical cases, but highest in mild cases. Serum 25(OH) D levels were statistically significant among clinical outcomes. Majority had insufficient vitamin D status, most of them were not severe. Vitamin D status is significantly associated with clinical outcomes.” (6)

Source of Vitamin D

Through Our Skin

The best way for our bodies to get vitamin D is through our skin via casual sunlight exposure. When our bodies come in contact with ultraviolet B (UV-B) rays, our skin makes vitamin D. It is important to get outdoors, be active, all while maintaining social distancing. The more time you spend indoors, the more likely you are to be vitamin D deficient.

Vitamin D and sun exposure

Sun exposure can also lead to an increased risk of skin cancer. However, sunscreen does block the body's ability to synthesize vitamin D. Aim to spend 10-20 minutes in the sun without wearing sunscreen. If you have darker skin or live farther north (northern hemisphere), you need more time in the sun. You may need as much as up to an hour a day of sunlight exposure. If you have lighter skin, you need less time. Keep in mind that the amount of sun exposure needed varies upon how close you live to the equator and how much of your skin is exposed. Talk to your dermatologist about vitamin D production and how much sun exposure is right for you.


Vitamin D supplement

According to the USDA, the recommended dose for vitamin D is 600IU/day for adults. However, many people are deficient and need higher doses. It is important to note that vitamin D is a fat soluble vitamin and therefore it is important to not over supplement. Talk with your doctor to determine your vitamin D levels and how much vitamin D you should be taking to get your levels to a healthy place. 


Vitamin D rich food

Some foods provide vitamin D but sunlight is still your best way to obtain it. Make sure to read food labels as many foods are fortified with vitamin D. Here is a list of some foods that contain vitamin D.

  • Mushrooms, in particular maitake and portobello mushrooms.
  • Halibut
  • Mackerel
  • Eel
  • Salmon
  • Tuna
  • Eggs
  • Fortified pasteurized milk and raw milk
  • Whitefish
  • Cod liver oil

Vitamin D plays a critical role in the health and well being of every individual. It supports bone health, protects against cancer and heart disease, helps regulate blood sugar, improves mood, regulates hormones, boosts immunity, and so much more. Talk to your doctor about having your vitamin D levels tested and how much vitamin D is right for you. 

Dr. Danielle Signature


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