Are you getting enough vitamin D to protect you against COVID-19 and other virus infections?
Active vitamin protects us against virus infections in a number of different ways. Vitamin D also controls the inflammatory processes and prevents them from becoming complicated. In a review article published in World Journal of Virology, scientists have pored over multiple meta-analyses and placebo-controlled studies that show a clear relation between vitamin D deficiency and an increased risk of respiratory viruses such as COVID-19 and influenza. Being vitamin D-deficient can also increase the risk of these infections turning into SARS (severe acute respiratory syndrome) that can result in potentially life-threatening circulatory failure and organ failure. Apparently, vitamin D plays an important and overlooked role in the prevention of virus infections.
Most of the body’s cells have vitamin D receptors (VDR) that regulate a host of different gene activities by controlling on-off switches. Vitamin D is of vital importance for our bone health, mood, insulin sensitivity, and general health. Vitamin D’s role in the immune defense is rather complicated, and in their review article the authors address the following topics:
- Physical barrier
Vitamin D helps to maintain strong physical barriers on the mucous membranes to prevent pathogens from penetrating and replicating. - The innate immune defense
Vitamin D is important for activating most white blood cells, including the NK cells (natural killer cells), monocytes, macrophages, and granulocytes that contribute to the body’s first line of defense against viruses and pathogens. Vitamin D also helps the white blood cells produce antimicrobial peptides such as cathelicidin and defensin that are defense molecules. The antimicrobial peptides in the respiratory tract normally provide good protection against virus infections and other airborne infections.
The innate immune defense is normally able to fight off pathogens without any symptoms. The innate immune defense can also launch an acute inflammatory response and call for assistance from the adaptive immune defense. - The adaptive immune defense
Vitamin D is important for different T cells that fight viruses and abnormal cells. T cells release different cytokines that affect the inflammatory processes. Vitamin D is also important for B cells that fight bacteria and stimulate the production of antibodies.
Vitamin D generally supports the communication of white blood cells, including the inflammatory processes targeted against pathogens. These processes must be controlled in time to prevent them from causing damage to health tissue or causing other complications.
COVID-19 and vitamin D
COVID-19 is a special type of coronavirus with problematic spike proteins on the cell surface. The spike proteins are able to attach to different cell types with so-called ACE2-receptors. If the innate immune defense doesn’t function optimally, COVID-19 attaches to nasal cells, replicate, and spread to other cells with ACE2-receptors in the airways, blood vessels, etc. In severe cases, the infection may develop into acute respiratory distress syndrome (ARDS), which is caused by cytokine storm and hyperinflammation in the lung tissue. Hyperinflammation and oxidative stress may also occur in blood vessels, kidneys, and other organs with cells that have ACE2-receptors. This may result in organ failure and death in worst case.
The ACE2-receptors are a key component of RAAS (the renin-angiotensin-aldosterone-system) that controls blood pressure by regulating the amount of fluid in the body. A weak and derailed immune defense combined with COVID-19’s ability to attack cells equipped with ACE2-receptors may explain why many of the symptoms occur when these tissues and organs are infected, and why the processes can easily become unhinged.
A large study involving 19 European countries showed that low blood levels of vitamin D increases the risk of complicated COVID-19 infections, hospitalization, and death.
In their review article, the authors mention numerous studies and meta-analyses that show how vitamin D protects against COVID-19 by supporting the innate and adaptive immune defenses. Vitamin D is also needed to avoid infection or to keep it under control.
Vitamin D can regulate RAAS, which is affected in complicated cases of COVID-19.
It appears that high-dosed vitamin D supplements that can optimize blood levels of the nutrient can reduce the severity of the infection and lower mortality among patients infected with COVID-19.
- There is a good reason why virus infections such as COVID-19 and the flu typically circulate during the winter period, when the sun sits too low in the sky for us to be able to synthesize vitamin D in our skin
- To make matters worse, the official guidelines for vitamin D intake cannot guarantee optimal levels of vitamin D in the blood
Influenza, colds, and vitamin D
There are many different types of influenza, but vitamin D generally has a protective effect via the innate and the adaptive immune defenses. If a person lacks vitamin D, the risk of becoming infected goes up. Also, there is an increased risk of bacteria (especially pneumococcus) from the microflora in the upper respiratory tract spreading to the lungs and causing bacterial pneumonia. Each year, millions of people around the globe die of this condition, especially older people. According to a large Danish study, lack of vitamin D can increase the risk of bacterial pneumonia by up to 60 percent.
Severe cases of the flu as well as severe COVID-19 can also develop into life-threatening ARDS that is a result of cytokine storm and hyperinflammation in the lungs.
Several randomized controlled studies have shown that vitamin D supplementation can lower the risk of influenza. Although very few studies have looked at vitamin D’s ability to prevent the common cold, it is advisable to always have enough vitamin D in the blood to support the immune defense.
Vitamin D’s metabolism, magnesium, and other nutrients
Our diets only provide small amounts of vitamin D. At northern latitudes, the sun during the summer period is our primary source of vitamin D, which we synthesize from a cholesterol precursor in our skin. This form of vitamin D is inactive and needs to be converted in the liver into the form of vitamin D that is measured in the blood (25-hydroxyvitamin D). When the body needs vitamin D, it then converts this form of the vitamin into the active form (1,25 (OH) 2D3) that is a steroid hormone. This process is handled in the kidneys, in the white blood cells, and in other tissues.
It is also important to get enough magnesium, which is needed to handle the enzyme processes that convert vitamin D into its active steroid form. Lack of magnesium will therefore impair the effect of vitamin D, even if levels of vitamin D in the blood are optimal. Also, zinc and omega-3 fatty acids are important for the activation of vitamin D and for the vitamin’s different immune functions.
How much vitamin D does the immune system require?
The Veterinary and Food Administration in Denmark recommends daily supplementation with vitamin D (5-10 micrograms) for everyone during the winter period. Vulnerable groups, seniors, and people with dark skin are advised to take 10-20 micrograms of vitamin D all year round. These recommendations take bone health into consideration but do not take other things into account such as the immune defense. Also, vitamin D requirements may vary from one person to another due to genetic factors BMI, chronic illnesses, etc. In any case, it is important to make sure to have optimal levels of vitamin D in the blood all the time.
Measuring vitamin D levels in the blood
- Blood levels of vitamin D are measured as 25-hydroxyvitamin D
- The official threshold value is 50 nmol/L
- Leading experts say that the level should ideally be 75-150 nmol/L for optimal disease prevention
References:
Muhammet Mesut Nezir Engin, Öner Özdemir. Role of vitamin D in COVID-19 and other viral infections. World Journal of Virology. 2024
Yunus Colak, Børge G Nordestgaard, Shoaib Afzal. Low vitamin D and risk of bacterial pneumonias: Mendelian randomisation studies in two population-based cohorts. BMJ 2020
Amar S. Ahmad et al. Association between Average Vitamin D Levels and COVID-19 Mortality in 19 European Countries – A Population-Based Study. Nutrients 2023
Intermountain Healthcare: New study finds current dosing recommendations may not help patients achieve optimal levels. EurekAlert. 2023
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