Does Vitamin D Support The Immune System Against Corona And Other Viruses?
It has not been researched whether vitamin D protects against the coronavirus. Does the vitamin have a preventive effect against infection with other viruses? Probably not, show studies on runny nose and co.
What are we going to do?
Taking vitamin D is said to strengthen the immune system and prevent some infections with viruses. This is at least promised by advertisements for various dietary supplements with vitamin D.
In times like these, a fit immune system is particularly in demand: You can also protect yourself against the coronavirus with vitamin D supplements, you can read on the Internet.
We started looking for the latest knowledge. Can the immune system be spiced up with vitamin D supplements? So much so that the coronavirus can no longer harm you? And are you protected against viral respiratory infections such as colds, dandruff and flu?
Anti-corona effect not plausible
We were unable to find any studies on vitamin D preparations and infections with the novel coronavirus. We also looked for studies on his close relatives SARS and MERS coronaviruses – without any result.
It is not plausible that taking vitamin D supplements could protect against infection with the coronavirus. Because colds and similar viral infections cannot prevent vitamin D preparations.
Vitamin D: Colds are not uncommon
Because according to the current state of knowledge, vitamin D preparations probably do not protect against respiratory infections caused by viruses. This applies to people who have no or only a moderate lack of vitamin D. That means that the vitamin can hardly be used to prevent colds, colds, flu or sinus infections.
This resulted in a current summary of 25 well-done studies. A total of over 11,000 children and adults took part in these studies.
The participants all had colds of a similar frequency – regardless of whether they were taking a vitamin D supplement or a dummy drug. In both groups, the participants had to fight about two colds a year.
Effects only when there is a shortage
The situation was different for those whose blood vitamin D levels were dangerously low at the start of the study. These people should benefit from vitamin D supplements because they were less likely to get sick in the study.
Better less, but more often
It may also be important for people with vitamin D deficiency how often they take the supplements. In the studies, some people received a large amount of vitamin D at a time and then paused for longer. Others swallowed small amounts daily or weekly.
Those had fewer colds, the smaller amounts and had taken them more often. The research team suspected that the body cannot use a lot of vitamin D at once.
Who has a shortage?
From what amount of vitamin D in the blood do people count as adequately supplied? That is far from certain. There are still passionate discussions about the limit values.
The information differs depending on the specialist society. Most experts were able to agree on a limit value of 50 nmol / l (or 20 ng / ml) in the blood. Lower values are considered inadequate – but only in relation to bone health. Values below 25 nmol / l (or 10 ng / ml) are classified by all experts as a serious deficiency.
How these limit values are set is not irrelevant: if they are too high, many people find a “deficiency”. And that despite the fact that they actually have no shortage.
You may then swallow supplements that in the best case involve money wasted. In the worst case, there are side effects. High doses of vitamin D can be problematic. More than 120 nmol / l vitamin D in the blood are considered harmful.
Old people particularly at risk
If you are out and about more often and eat a balanced diet, you do not have to be afraid of harmful vitamin D deficiency. At least that is the case in Central Europe.
In order to be well supplied with vitamin D, it is enough to spend about 5 to 15 minutes a day in sunlight, in autumn a little longer. Even if only the face and hands are uncovered, enough vitamin D is formed in the skin.
However, some people are at higher risk of vitamin D deficiency. This includes, for example, people who are mainly indoors, for example, the residents of care facilities. People who are not exposed to the sun for other reasons, such as fully veiled women, are also at risk.
Various intestinal diseases can also lead to the deficiency if this hinders the absorption of vitamin D from food.
Vitamin D should not be taken “just like that”. In principle, severe vitamin D deficiency is rare in this country. A blood test for vitamin D deficiency is only recommended by specialist societies for older or chronically ill people and for those who are hardly exposed to the sun.
Vitamin D for hard bones
The body produces most of the vitamin D it needs. For this, he needs sunlight, which should hit the skin unfiltered if possible. A smaller part comes from food, for example from fish, eggs or liver.
Vitamin D is involved in many processes in the body. It influences the absorption and processing of calcium and is therefore important for healthy bones. Permanent vitamin D deficiency can lead to reduced bone density (osteoporosis).
In children, a severe deficiency can soften the growing bones and trigger rickets. In the past, children were often given cod liver oil to prevent this symptom. The oily liquid is made from fish liver and is rich in vitamin D. In times of one-sided and poor nutrition, cod liver oil helped prevent rickets.
Legendary reputation – undeserved
Apart from bone health: the role of vitamin D in health has not been well researched. But we now know that vitamin D is important for a normally functioning immune system. It is therefore plausible that the body’s defences are weakened in the event of a serious deficiency.
The vitamin is also said to protect against cardiovascular diseases, allergies, cancer and Alzheimer’s. Many of these claims have since been refuted.
We have also reported on this several times:
- Vitamin D does not protect against cancer
- Allergy trigger vitamin D?
- Dementia: Does Vitamin D Keep Your Memory Fit?
- Vitamin D in pregnancy
- Vitamin D overrated as a pain reliever
But where does the legendary reputation of the vitamin come from as a miracle cure? On the one hand, there is an observation that most body cells have docking points for vitamin D. On the other hand, it seems that people with high vitamin D levels are less likely to get sick.
This observation may be correct. But it does not mean that vitamin D is the cause of good health. It could also be a “side effect” of good health.
Perhaps it is an outdoor exercise that both keeps you healthy and replenishes your vitamin D stores. It could also be the case that healthy people are more likely to be outdoors than sick people.
Vitamin D blood tests are usually not necessary
According to current knowledge, the fear of vitamin D deficiency is probably not justified. What is refuelled in spring, summer and autumn also supplies the body in winter? Because vitamin D is stored in the body for several months.
[The first version of this article was published on October 31, 2013. This version is the third update. New studies have confirmed our previous assessment and confidence in the result has increased.]
The studies in detail
We searched for three different scientific databases for the latest studies.
No studies on corona
We were unable to find any studies on the subject of coronavirus and vitamin D. We believe that taking vitamin D has a preventive effect against SARS-Cov-2 infection is not plausible.
Probably no effect with colds and co
We found a well-performed review from 2019 on vitamin D and the prevention of viral respiratory infections. It summarizes the results of 25 randomized controlled trials.
All of these studies looked at the following question: Do people who take vitamin D supplements get infections of the upper respiratory tract less frequently? This includes runny nose, cough or sinus infections.
A total of 11,321 men and women from 15 countries took part in these studies, from newborn to very old. The participants were initially well supplied with vitamin D in different ways: The measured values in the blood ranged between approximately 19 and 89 nmol / l.
The participants were randomly divided into two groups. One group swallowed a vitamin D preparation, the other a dummy preparation (placebo).
Dosage and frequency of intake were different: some took a larger amount of vitamin D every three months, others swallowed it daily or weekly, but smaller amounts. The participants did not know whether it was vitamin D or a placebo.
The taking lasted between seven weeks and a year and a half. During this time, it was recorded how often the participants got a cold or another respiratory infection.
Effect only in the case of severe deficiency
The research team of the review also analyzed whether the vitamin D level at the start of the study influenced the later likelihood of illness. With normal or moderately low vitamin D levels, the additional vitamin D is unlikely to have any effect on the risk of catching a cold. In both groups, the participants became ill on average twice a year.
Only those participants who had a severe vitamin D deficiency with a value of less than 25 nmol / l became ill a little less frequently.
Better less, but more often
What the research team also wanted to know: Do the dosage and frequency of use play a role? The researchers found that people who swallowed a large amount of vitamin D every three months (over 30,000 IU) had as many colds as the placebo group.
The situation was somewhat different for those who took vitamin D daily or weekly: at least they had a slightly better chance of getting through the year healthily than the placebo group. However, the effect was only very small here.
Side effects unlikely
The conclusion of the review: For people who have no or only a moderate deficiency, vitamin D preparations for the prevention of colds are probably not effective.
No side effects of vitamin D supplements were observed in the studies. So they did not appear to have harmed the health of the participants.
We have quite a lot of confidence in these results. The overview work is methodically flawless, and the data of the more than 11,000 participants are very reliable.