Does vitamin D support the body’s own COVID-19 defence?

The general benefit of vitamin preparations has long been debated among experts. Many consider them superfluous and recommend a balanced, fresh diet.  However, and this has long been recognized by scientists, vitamin D is the only substance in this group that plays a special role. Our body can easily produce it itself in the skin with the help of the sun. But this is exactly where the problem lies because from late autumn to early spring, the power of the sun in countries like Switzerland is not sufficient for this. This assessment is also shared by the Federal Office of Public Health (FOPH).

In the following, we describe the essential effects of vitamin D and provide decision support for the preventive use of this sun vitamin.


Main tasks and the special role of vitamin D

Vitamins are regarded as indispensable building blocks of life. Only through them can certain metabolic processes take place in the organism. If there is a deficiency, this can lead to serious disorders of organs and the immune system. From the very first day of life, vitamin D, also known as the sun or light vitamin, plays a decisive role in how we develop externally and in terms of health.

The main tasks

The D vitamin supports and shapes these three areas in particular:

  • The formation and maintenance of an evenly formed skeletal structure with stable bones and healthy teeth.
  • The development of functional, strong muscles for the entire musculoskeletal system into old age.
  • The provision of a strong immune system against invading bacteria, viruses, and other pathogens.

The special role of vitamin D – an ideal concept of nature

With a balance between plant-based and animal-based foods, humans are sufficiently supplied with all the vitamins and nutrients they need. Only vitamin D is an exception. Since food only covers a small part of the requirement, nature itself has found a way to produce the main quantity needed. It uses the skin and the UVB light of the sun.

Only the human factor has not been taken into account, which is now proving to be a real “brake on production”. At least until the beginning of the industrial age with sunless factories and offices, self-production of the light vitamin was not a problem either, because living with nature was the rule for thousands of years. The modern lifestyle, however, has largely cut this connection and.


The current hype about vitamin D

This hype did not come all of a sudden. Due to the COVID-19, it is merely the current focus of discussion of a long-term evaluation phase of the health effects of the sun vitamin, which began about 20 years ago. Essentially, there are three topics that have been intensively dealt with since then and that shape the current view of this vitamin:


  1. Diet and lifestyle

Initially, Swiss and international experts were concerned with how gradually changing lifestyle and dietary habits generally affect vitamin D blood levels. Although this sounds simple, it is very time-consuming because it requires large population groups and studies lasting several years.

At the beginning of the study, the expert groups were still convinced that the sun fixes everything and provides the body with sufficient vitamin D in addition to the diet. However, the results were more than sobering and triggered the first discussion hype about the D vitamin. For in Switzerland as well as in other countries, it was shown that more than half of the population has a clear vitamin D deficiency.

At the same time, all experts were alarmed that our current lifestyle offers the summer sun only limited opportunities to produce the D vitamin in sufficient quantities. Both prompted the Swiss Society for Nutrition (SGE) in 2012 to comprehensively reassess the daily requirement of vitamin D for all age groups.


  1. Vitamin D as a prevention measure against Alzheimer’s, cancer, and cardiovascular diseases?

Science has been extremely active for years when it comes to the prevention of chronic diseases. With regard to vitamin D, Alzheimer’s disease, tumor diseases and various cardiovascular disorders were important examples.

The question was always whether good vitamin D blood levels can slow down or prevent these disease patterns. Even extensive studies on several tens of thousands of people have not yet shown the hoped-for improvements.


  1. Vitamin D and the body’s own defense

Of course, the current vitamin D hype also has a serious scientific background. The basic idea behind the corona pandemic is that an immune system that is optimally prepared to fight off COVID viruses is better than a weak immune system, especially since favorable vitamin D effects on respiratory infections and flu symptoms are known.

In 2013, well before the COVID-19 pandemic, Danish cell researchers contributed vivid knowledge about the biological immune processes in the body. They confirmed earlier assumptions that this vitamin stimulates the body’s own production of killers or phagocytes that fight off invading pathogens.

Based on these and other findings, doctors from the universities in Angers (France) and Córdoba (Spain) have tried in pilot studies to support corona-infected people in their body’s own defense by giving them vitamin D. The results were quite encouraging. The results were quite encouraging but are currently not sufficiently conclusive due to the small number of cases. Further studies are planned for a reliable answer.

Thus, there is currently no unequivocal evidence that vitamin D protects against severe COVID-19 infections. The Swiss Society for Nutrition expresses a similar opinion, which so far does not consider the light vitamin to play a major role in the fight against corona.


Decision-making aid for prevention with vitamin D

However, when looking at all the data, it remains undisputed that the D vitamin significantly supports the development of a strong immune system. Prof. Heike A. Bischoff-Ferrari, a proven vitamin D expert and director of the Clinic for Geriatrics at the University Hospital Zurich, argues accordingly.

It therefore makes perfect sense to make preventive use of the opportunities offered by the sun vitamin, taking into account the SBU recommendations outlined below.

Vitamin D requirements – what the Swiss Society for Nutrition recommends

Shortened to suit everyday life, their advice is easy to remember:

  • All people between the ages of 3 and 60, including pregnant and breastfeeding women, have a daily requirement of 15 µg (micrograms) or 600 IU (International Units).
  • Those who belong to this group and regularly spend time outdoors from June to September do not need supplements, at least in summer. In winter, however, supplementation is recommended.
  • Otherwise, additional vitamin D supplements are advisable all year round, for example as drops or tablets. Users should discuss any questions that may arise in individual cases with a doctor or pharmacist. Pregnant women and breastfeeding mothers should check with their doctor if they need vitamin D supplements.
  • From the age of 60, 20 µg or 800 IU daily is indicated all year round, as the skin’s own production decreases with age. Supplements are recommended, possibly in consultation with the doctor.


Generally important aspects for meeting the daily vitamin D requirement

The basis remains a varied, balanced diet based on the Swiss food pyramid. However, only a few foods such as fatty fish, eggs or porcini mushrooms are rich in vitamin D. Therefore, the daily diet contributes only 10 to 15 percent of the requirement.

The large remainder is provided by the summer sun. About 15 to 20 minutes in the sun on 3 to 4 days a week with uncovered face and hands is sufficient. The best time is between 10 am and 3 pm. In the winter months, however, the sunlight is too weak to set vitamin D production in motion.

Short sunbaths should always be done without sunscreen or facial care products with light protection because even a factor of 15 stops the body’s own production completely. As dermatologists point out, these few minutes are harmless to the skin. Immediately afterward sun protection is required again.

By the way, longer light showers than a maximum of half an hour are useless, because the body stops its daily production after this time. This is because the body manages to cover its daily requirements during this short period of time and also to store a reserve. The following day it is ready to produce again.

At what dosage does vitamin D become dangerous?

The safety range is very large by nature because the body can store its own supply for the winter for roughly 100 days.

The Federal Office of Public Health states 100 µg or 4000 IU as the daily tolerable upper limit, which is still considered safe. This recommendation, however, is directed at the medical profession, since this dosage already means five to seven times the SBU recommendations.

Vitamin D3 and vitamin D – the differences

On the sales packages of the supplements, depending on the manufacturer, you will find the designations vitamin D3 as well as vitamin D, but this has no meaning for the consumer.

Because in the end, it is vitamin D, which the body first produces from the particularly well-storable precursor vitamin D3. In our skin, by the way, the process is exactly the same: First the sun produces the D3 and later the metabolism makes vitamin D from it.

Vitamin D, combined with other vitamins

The effect of vitamin D in the dosages recommended by the SBU is not improved if a supplement contains additional components such as vitamin K2 or omega-3 fatty acids, etc. The effect of vitamin D in the dosages recommended by the SBU is not improved if a supplement contains additional components such as vitamin K2 or omega-3 fatty acids, etc.

For precautionary use, pure vitamin D is sufficient.  Other vitamins and nutrients are part of a balanced diet anyway, as suggested for example by the Swiss food pyramid.



  • Vitamin D is not a medicine to cure a corona disease.
  • However, the sun vitamin can – in addition to strengthening the musculoskeletal system (bones and muscles) – strengthen the body’s immune defence and thus support a favourable corona infection course.
  • In addition to a balanced diet based on the Swiss food pyramid and regular short stays in the summer sun, vitamin D supplements supplement the need.
  • Vitamin D products are available over the counter, for example as drops or tablets.
  • Depending on age, the Swiss Society for Nutrition recommends a daily dose of 15 to 20 µg (micrograms) or 600 to 800 IU (International Units) to cover requirements.