Adequate Vitamin D Level Strengthens the Immune System

The Covid-19 coronavirus crisis is teaching us that an adequate vitamin D level strengthens the immune system.

When we age, our resistance to infections weakens, but this may be because our immune system needs more vitamin D3. I have reviewed the super powers of vitamin D3 before in 2014. In the past the thought was that the human body would need only 400 IU of vitamin D3 every day to cure rickets. And these were the daily vitamin D3 recommendations from medical authorities for several decades. Gradually it became known that for cancer prevention, infection prevention, cardiovascular illness prevention and for diabetes prevention much higher doses of vitamin D3 were necessary. As pointed out in the previous link, almost 50% of the world population is deficient in vitamin D. This is due to a lack of exposure to sunlight and due to inadequate supplementation with vitamin D3.

History of vitamin D

Dr. Adolf Windaus received the Nobel prize for chemistry in 1928. It was to acknowledge “… his studies on the constitution of the sterols and their connection with vitamins”. His work involved the metabolism of vitamin D and the precursors of vitamin D.


As the above link shows, rachitic children were treated since the mid 1800’s with cod liver oil and since the early 1900’s also with ultraviolet light. But we know now that 400 IU of vitamin D3 per day is just enough to cure rachitic children, but it is not enough to strengthen the immune system to fight influenza viruses or the Covid-19 coronavirus. I will discuss further below what vitamin D blood levels are important to achieve a healthy state of the immune system.

Adequate vitamin D level strengthens the immune system

The immune system is very complicated and consists of many cell types that interact with each other and the rest of the body. It is important to recognize that the innate immune system immediately inactivates intruding viruses. But the vitamin D blood concentration has to be high enough. The acquired immunity consists of antibodies that are produced by B cells. The antibodies were produced during prior infections that you have survived and you are now immune to. However, other antibodies that circulate in your blood may have originated from vaccines you received in the past (whooping cough, measles, tetanus, diphtheria etc.). With the Covid-19 coronavirus it is the innate immunity that plays the biggest role until a vaccine will be found in the future.

Vitamin D is a hormone

This 2013 paper explains that vitamin D is a hormone that stimulates its own vitamin D receptor. This is a nuclear receptor that has close relations to the cell DNA and can stimulate more than 900 polypeptides. They are messenger molecules that are involved in a variety of physiological functions. One of the key functions is the immune system. This link explains that T cells that have vitamin D receptors can develop into cytotoxic T cells (also known as “killer T cells”). They are important in fighting cancer, but also parasites.

The key is that the hormone vitamin D can release more than 100 polypeptides that have the power to fight virus attacks including the Covid-19 coronavirus.

Three mechanisms how vitamin D works against the virus

The researchers outlined 3 mechanisms of how vitamin D works:

  • Maintaining tight epithelial junctions making it more difficult for the Covid-19 coronavirus to penetrate.
  • “Killing enveloped viruses through induction of cathelicidin and defensins.” These powerful antiviral polypeptides can kill viruses that have invaded the blood stream within 1 to 2 days.
  • “…And reducing production of proinflammatory cytokines by the innate immune system, thereby reducing the risk of a cytokine storm leading to pneumonia.” It is people who get the viral pneumonia that are at a high risk of death. By bringing the blood level up to the higher range of normal, between 50 and 80 ng/mL, patients that have encountered Covid-19 coronavirus are more likely to survive.

Two polypeptides, cathelicidin and defensins

Again, I like to emphasize that it is not vitamin D that has a direct effect on the virus. It is two polypeptides, cathelicidin and defensins, which are powerful antiviral polypeptides, that are released by vitamin D.

They can kill viruses that have invaded the blood stream and can eliminate the cytokine storm. This all happens very fast, within only 1 to 2 days. But you have to have an adequate vitamin blood level for this to occur (about 50-80 ng/mL).

Sources of vitamin D

First of all, vitamin D is readily absorbed from food. But there are not many foods that contain enough vitamin D for the immune system. The ones that contain vitamin D are as follows:

  • “Fatty fish, like tuna, mackerel, and salmon.
  • Foods fortified with vitamin D, like some dairy products, orange juice, soy milk, and cereals.
  • Beef liver.
  • Cheese
  • Egg yolks. “

Sun induced amount of vitamin D

Secondly, vitamin D can be synthesized in the skin from exposure to sunlight. But for this to happen all the necessary enzymes need to be present.  This link explains that many older people above the age of 65 have low vitamin D blood levels because of a lack of sun exposure and a lack of cutaneous synthesis because of enzyme issues.

Vitamin D supplements

The most reliable source of vitamin D are vitamin D3 supplements. When people supplement with the same dose of vitamin D3 there will be people who get higher vitamin D blood levels than others, as absorption in the gut is different for different people.  The ones who have relatively low vitamin D blood levels are often called “slow vitamin D absorbers”. But when the vitamin D3 dosage is increased even those people will reach the recommended high normal range (50-80 ng/mL).

Vitamin D blood level

The vitamin D blood test has the scientific name “25-hydroxy vitamin D level”. This is now the recognized gold standard for determining who is deficient or has normal levels with respect to vitamin D. The following 2013 publication has studied the vitamin D level of 1,470 healthy Swiss men and women, 60 years or older. Vitamin D levels were classified as severely deficient when the level was below 10 ng/mL. The vitamin D level was deficient between 10 and 20 ng/mL. The level was insufficient when between 21 and 29 ng/mL. A level above 30 ng/mL is normal.

8 % of the subjects were severely insufficient and 66% had insufficient vitamin D levels. Only 26.1% of the subjects had normal levels. Over 50% of healthy older Swiss (above the age of 70) had insufficient vitamin D levels.

Which vitamin D level is safe and which is not?

A peer-reviewed publication of the effects of vitamin D in health and disease contains 269 references.

What vitamin D level is optimal? This question was reviewed in this paper.

  • Below 15 ng/mL the immune system is paralyzed
  • With a level above 30 ng/mL the immune system is working
  • A level of 50-80 ng/mL has the immune system working optimally
  • Above 150 ng/mL toxic vitamin D levels start
  • With 300 ng/mL severe toxicity begins

Vitamin D toxicity

It is only with high levels of vitamin D (more than 150 ng/mL) that you have to worry about high calcium levels in the blood or kidney stones (toxic levels). But the key is to not exceed 80 ng/mL regarding the vitamin D blood level. This gives you a lot of flexibility before you reach toxic levels (above 150 ng/mL). For those who want more information, here is a thorough, peer reviewed publication about vitamin D toxicity with 59 references.

Vitamin D supplement compliance

The question is why not more people take adequate vitamin D3 supplements.  We know that vitamin D can prevent so many chronic diseases including serious viral infections. The answer is complex, but it includes a fear of the population of vitamin toxicity (kidney stone and high calcium levels). However, as pointed out before, this occurs only above a vitamin D level of 150 ng/mL. With proper vitamin D blood level monitoring you never reach toxic levels of vitamin D.


Denial likely is another major factor. People feel that if they have a balanced diet, they would be protected from vitamin D insufficiency. As pointed out before this is a grave error to think as our food does not contain sufficient vitamin D to strengthen our immune system.

False security with low doses of vitamin D

Finally, there are people who think that low doses of vitamin D, like 1000 IU of vitamin D daily, would be enough. But it is not enough. This is why testing vitamin D blood levels is so important. It is a reality check. The blood level must be in the high normal range (50-80 ng/mL). At this level the immune system functions optimally.

Compliance issues

In this context there was an interesting study done by LifeExtension, a company that publishes monthly health magazines. In this study the company examined the vitamin D blood levels of LifeExtension members. They are the ones who should be knowledgeable in how important it is to have good, preventative vitamin D blood levels. The study showed that 38% of the vitamin D test results were less than 30 ng/mL. In addition, 69% of the vitamin D tests were less than 40 ng/mL. Finally, 85% of the vitamin D test results were less than 50 ng/mL. What this means is that LifeExtension members were non-compliant when it came to taking regular adequate vitamin D3 doses. This resulted in levels that were too low for the majority to protect them from the Covid-19 coronavirus.

Covid-19 coronavirus infections and vitamin D blood level

There is a tight relationship between vitamin D blood levels and the strength of the immune system. Essentially, coronavirus mortality measures who is vitamin D deficient. Without enough vitamin D on board the virus penetrates into the blood stream and penetrates the lining of the respiratory tract. Next the cytokine storm develops, which leads to viral pneumonia. Higher doses of vitamin D3 will mitigate the course of Covid-19 coronavirus.

Adequate Vitamin D Level Strengthens the Immune System

Adequate Vitamin D Level Strengthens the Immune System


The Covid-19 coronavirus pandemic has taught us how important an intact immune system is to survive the virus when you get it. We do know for some time how closely related a good vitamin D level is with the functioning of the immune system. I have reviewed here what a desirable vitamin D level is and how we can achieve this with oral vitamin D3 supplements. The goal is to achieve a vitamin D level in the upper range of normal (50-80 ng/mL). With a level like this the virus cannot penetrate the mucous membranes of the respiratory tract and even if it did, it cannot produce a cytokine storm in the blood that would lead to the deadly viral pneumonia or to blood clots. When the virus invades the bloodstream, vitamin D releases powerful antiviral polypeptides that can kill viruses within 1 to 2 days.


Here are some peer-reviewed publications on vitamin D:



The Superpowers Of Vitamin D


This article deals with the superpowers of vitamin D. Originally, researchers found that vitamin D was the missing ingredient in preventing rickets in growing children. They established that 400 IU of vitamin D daily prevented rickets. Medical investigators determined that the active metabolite was vitamin D. The body has receptors on all vital organs for vitamin D. This includes the heart, brain, bones, kidneys and liver. In recent years new findings showed that the RDA of 400 IU of vitamin D3 daily was too low for many diseases. In other words, many diseases can develop when vitamin D intake is too low, particularly in the aging population. Researchers showed that higher doses of vitamin D3 in the range of 800 to 1000 IU per day prevent osteoporosis, falls and fractures in older adults and in nursing home populations.

The immune system requires higher doses of vitamin D3

But the immune system of everybody is dependent on higher doses of vitamin D3. Recently (Dec. 12 to 15, 2013) I attended a lecture at the A4M conference in Las Vegas where Dr. Eisenstein reviewed the latest on vitamin D3. It is now known that 2/3 of the US population is deficient for vitamin D as measured by blood tests (less than 25 ng/ml).  The standard test is the 25-hydroxy-vitamin D level (abbreviated as 25(OH)D level). It is now known that you require at least a level of more than 40 to 60 ng/ml of 25(OH)D as measured in the US, which translates to more than 100 to 150 nmol/L measured in metric units in other countries, to prevent cancer.

The Super Powers Of Vitamin D

The Super Powers Of Vitamin D

Metabolism of vitamin D3

90% of the vitamin D3 that we need comes from exposure to sunlight. This transforms a cholesterol metabolite (7-dehydrocholesterol) into the vitamin D precursor (vitamin D3 or cholecalciferol). We absorb this from naturally occurring fish oil and oily fish. Otherwise this does not naturally occur in foodstuffs (Ref. 1). Dr. Eisenstein pointed out that it is well known that people living north of the 37th degree latitude lack vitamin D3 because of a lack of sun exposure, particularly in the winter season. People south of the 37th degree latitude have enough sun exposure. But wherever you live, it is advisable to have your vitamin D3 level measured (as 25(OH)D level). If you do not eat enough fish or fish oil, the levels likely are too low as is the case for 2/3 of the US population.

Oral vitamin D3 supplements

Patients whose vitamin D levels are too low have to take vitamin D3 supplements. Vitamin D3 is further metabolized by the liver and then by the kidneys into the active vitamin D compound, called 1,25(OH)2D3 (which is called “calcitriol”). The main effect of calcitriol is to absorb calcium and phosphate from the intestine into the blood stream. Together with vitamin K2 as explained in a prior blog these minerals are then taken up by the bone to prevent osteoporosis or rickets in the growing child. What has not been known for a long time is that vitamin D3 is also necessary for normal cell metabolism by most of your body cells, but particularly by the vital organs like the brain, the heart, the kidneys, the liver, the immune system and the bone.

Some people require higher doses of vitamin D3

However, doses of 5000 IU to 10,000 IU of vitamin D3 capsules per day are necessary for optimal vitamin D3 health. This leads to levels of below 150 ng/ml of 25(OH)D levels, which were shown by researchers to be safe. According to Dr. Eisenstein no toxicity has been found below 30,000 IU of vitamin D3 per day, but based on other authors a dose of 10,000IU should be adequate for most people. Strangely enough colored people also have to take vitamin D3 supplements as the higher melanin pigment in the skin filters out UV light so effectively that their 25(OH)D level can be low. Always err on the cautious side and have your vitamin D3 blood level taken. Vitamin D3 has a characteristic stereotactic configuration (cis-triene structure), which allows it to bind free radicals and function as an antioxidant (Ref.2).

What are some of the clinical effects of vitamin D3?

  1. Vitamin D3 has diverse effects on organs systems as Dr. Eisenstein summarized: vitamin D3 lifts depression and is of particular value for drug resistant depression. Take 5000 to 10,000 IU of vitamin D3 per day.
  2. Muscle power increases with vitamin D3, particularly in those who work out regularly.
  3. Many fertility clinics pay attention to vitamin D3 levels, as the higher the blood levels of vitamin D3 in a man, the faster this sperms move! And the more vitamin D3 she has on board, the better she ovulates. The end result is a higher pregnancy success rate when both partners take 5000 to 10,000 IU of vitamin D3 per day

Vitamin D improves teeth in offspring, helps with chronic pain

  1. Also, if a woman takes vitamin D3 during her pregnancy, the first set of teeth in the offspring will have fewer cavities.
  2. Brain development in autistic children is much improved with vitamin D3 in higher doses. This needs to be combined with detoxification methods and supervised by one of the DAN physicians.

6.Chronic pain typically improves when physicians treat vitamin D3 deficiency, which almost always is present in patients with chronic pain.

Prevention of flus and Covid-19, asthmatics improve

  1. To prevent flus and colds and other infectious diseases, take higher doses of vitamin D3. When you come down with a flu, it is safe to increase your daily vitamin D3 intake to 30,000 IU of vitamin D3 for a few days until your symptoms improve, then resume your maintenance dose of 5000 IU to 10,000 IU per day.  This year’s dominant flu is the type A, subtype H1N1 – also known as the swine flu. Children should get 50% of the dose regimen detailed for adults when they develop a flu (for children: 15,000IU for three to five days , with tapering to a maintenance dose of 2500 to 5000 IU until blood levels of 25(OH)D are available). Here is a website about the pros and cons of vitamin D where dosages are also discussed.
  2. Asthmatic patients do better with vitamin D3 supplements requiring less maintenance anti-asthmatic medicine to keep them balanced with regard to their airways.

Partial prevention of Alzheimer’s disease with vitamin D

  1. Chronic low vitamin D3 levels cause brain damage including Alzheimer’s disease. In this context it is important to know that the enzymatic conversion in the liver and kidneys slow down as we age.  Older patients require higher doses of vitamin D3. This may have been the reason for the confusion about relatively low doses of 400 IU of vitamin D3 preventing rickets in children versus the need for much higher doses of vitamin D3 in middle aged and older patients.
  2. There is a link of high blood pressure to vitamin D3 deficiency and it is better manageable with medication when vitamin D3 levels are normal.

Vitamin D lengthens telomeres and increases longevity

  1. Live longer with vitamin D3. How is this possible, you might ask: the answer has been found in the telomeres, the shoelace like structures at the end of the DNA strand of each cell. Vitamin D3 lengthens the telomeres and promotes telomere repair; there is an association of vitamin D3 and a longer life span. Centenarians have longer telomeres. You can measure telomere length, but it is a pricey test, which is not for everyone, contrary to supplementation with vitamin D3 that should be taken by everyone!

Vitamin D fights inflammation

  1. As already indicated, vitamin D3 strengthens the immune system. But it also modulates the inflammatory response from muscle damage, so athletes can perform better. Patients with multiple sclerosis will improve as it slows down the inflammatory process. But other inflammatory diseases like arthritis, inflammatory bowel disease and even cancer respond favorably to higher doses of vitamin D3. In these cases physicians use 20,000 to 30,000 IU of vitamin D3 daily. This information has not yet percolated into mainstream medicine.
  2. Higher percentages of cardiovascular disease occur in patients who have lower than 15 ng/ml  25-Hydroxy-vitamin D levels in their blood meaning that vitamin D3 supplementation prevents heart disease (Ref.3).

What are toxic vitamin D levels?

What is known about the safety of vitamin D3, particularly the higher vitamin D3 doses? First, it is wise to have your 25(OH)D blood levels taken from time to time. If vitamin D blood levels exceed 150 ng/mL reducing the vitamin D dose or stopping supplementation is prudent. Otherwise it has been difficult to establish a toxic range. Most publications about toxic levels of  vitamin D point out that anything above 150 ng/mL would be in the toxic range.

This website claims that 40,000 IU of vitamin D3 or more would lead to toxic levels where the blood calcium levels would be increased, which can be measured as hypercalcemia. However, another study done in 2007 showed in MS patients that took 40,000 IU per day and that led to a blood level of 400 ng/ml of 25(OH)D did not lead to increased calcium levels and did not lead to hypercalciuria (too much calcium in the urine).

Toxic vitamin D levels difficult to find

The papers that indicated that it would be unsafe or unnecessary to take vitamin D3 were untrue. It seems that they had other agendas than communicating the truth. There was no release of calcium from the bones and calcium absorption from the gut was not too high. This would have caused calcification of the bones, soft tissues, heart and kidneys. Also, kidney stones would have developed. However, a low calcium diet combined with corticosteroid drugs usually leads to a full recovery within a month. Interesting that all of the dire predictions regarding toxic vitamin D3 levels did not materialize. Here is another website discussing vitamin D3 dosing.

Patient taking unintentional high doses of vitamin D3 survived

I talked to a participant of the conference with a fellowship degree in anti-aging medicine what knowledge we have about vitamin D3 toxicity. He told me that there has been an unintentional overdose. In this case a compounding pharmacy made a mistake. A patient accidentally received a dosage of 500,000 Units of vitamin D3 per day for a full three months. The patient felt sluggish, but did not have any other symptoms. His physician told him to stop the vitamin D3 compound. He had an uneventful recovery with no detrimental effects. At this point no documented overdose of vitamin D3 exists.


Vitamin D3 is a vital supplement. Initially researchers showed that it prevents rickets in children. Subsequently physicians found that it also prevents depression, MS, infections and many cancers (Ref. 4). As usual there will be many critiques that doubt the validity of the above statements. But I have found that all of these effects described above were confirmed in several sources of various medical information. Keep in mind that negative rumours have a tendency to linger on for years.

More information on vitamin D3 for prevention of osteoporosis and hardening of arteries: https://www.askdrray.com/calcium-vitamin-d3-and-vitamin-k2-needed-for-bone-health/

Vitamin D3 deficiency can cause pancreatic cancer: http://nethealthbook.com/news/insufficient-vitamin-d3-linked-to-pancreatic-cancer/


1. McPherson: Henry’s Clinical Diagnosis and Management by Laboratory Methods, 22nd ed.,  © 2011 Saunders

2. Rheumatic Diseases Clinics of North America – Volume 38, Issue 1 (February 2012) , © 2012 W. B. Saunders Company

3. Wang TJ, Pencina MJ, Booth SL, et al:  Vitamin D deficiency and risk of  cardiovascular disease.   Circulation 117. (4): 503-511.2008.

4. “Recognition and Management of Vitamin D Deficiency”: American Family Physician – Volume 80, Issue 8 (October 2009),  © 2009 American Academy of Family Physicians