Without sun, life is not possible. This applies to plants and animals – as well as to humans. We need sunlight to produce the important vitamin D, which is therefore often referred to as the “sun vitamin”. Vitamin D is necessary for many processes in the body (e.g. for maintaining normal bones, teeth, and muscles). Because of our 21st century lifestyle, vitamin D synthesis has become difficult for large parts of the population. Read on to find out what the “sun vitamin” is and how it is produced in our bodies.
Far-reaching influence of the sun
Vitamin D plays a key role in the human body because it is responsible for countless tasks. For example, it ensures that the intestines can absorb calcium and phosphorus from food. It is also involved in the maintenance of muscles, bones, and teeth and supports the function of the immune system. It is also known that vitamin D receptors are present in almost all organs and tissues; this has a far-reaching influence on the metabolic processes in the intestines, brain, heart, pancreas, skin, and lymphocytes.
Ensuring an adequate supply – easier said than done
Some 80–90% of our vitamin D requirement can be met by the body itself with the help of sunlight – but only if the right conditions are fulfilled. North of the 42nd parallel, we are not able to make vitamin D during the winter months. This is because the synthesis of vitamin D in the skin is strongly dependent on the UV-B index, which only reaches the required value of more than 3 – equivalent to UV-B radiation of 290–315 nm – when the sun is at the right position or angle.
A simple rule of thumb: If your shadow is longer than you, vitamin D synthesis is not possible.
Vitamin D can also be ingested via food. However, various European nutrition societies agree that it is difficult to obtain an adequate supply from normal dietary sources. This is also stated in the Austrian nutrition report. Liver and high-fat fish (e.g. salmon and herring) contain higher concentrations of vitamin D but are rarely on the menu. Egg yolk, milk, and dairy products, on the other hand, have lower quantities. Without sufficient exposure to sunlight – in winter or when spending long periods of time indoors – nutrition in combination with sunlight is not sufficient to reach the reference value of at least 800 IU (international units) specified by the German Society for Nutrition (Deutsche Gesellschaft für Ernährung, DGE). Taking vitamin D supplements is therefore recommended.
The groups of people who should pay particular attention to their vitamin D levels include:
- pregnant women & nursing mothers
- infants, children & young people
- older people
- shift workers
- dark-skinned people
- people who keep themselves covered up
The three basics of vitamin D supply
Finally, we would like to give you three facts that you can use to ensure a stable vitamin D level in all life situations:
- The body can use sunlight to produce Vitamin D itself. Sufficient UV-B radiation must therefore be ensured. A tip from the editorial team: Most weather apps also provide information about the current UV index.
- Vitamin D can be absorbed from food – but it is difficult to obtain the recommended daily intake of 800 IU in this way.
- In order to cover daily needs and prevent depleted vitamin D stores, the Nutrition Society recommends taking vitamin D supplements.