Vitamin D and its benefits

Vitamin D includes ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Humans can produce it in sufficient quantities in their own skin. This characteristic is unique among vitamins.

The sun first

To make vitamin D, the skin must be exposed to sufficiently intense sunlight. If the sun's intensity is low, we wear too much clothing or don't go out in the sun, there is no production. Under certain conditions, it would be possible to produce enough. However, fear of skin cancer leads us to avoid the sun or to constantly slather on sun cream. A sun protection factor of 8 is enough to prevent the formation of vitamin D. Food contains little vitamin D, and without sunlight it is difficult to produce it. If you don't eat 300 grams of oily salmon a day, you can't get by without the sun. The alternative then is to take supplements.

Filling up in summer for winter

In winter, we no longer produce vitamin D in the skin due to weaker sunlight, even if we're outside in the fresh air. This is why we should often fill up on sunlight in summer and build up our reserves. The vitamin D stored in fat helps us to get through the winter months with little sunshine. It's important to expose yourself to the sun, even without sun cream, without burning yourself of course.

What is the recommended exposure?

The formation of vitamin D depends essentially on the type of skin as well as the season. The Federal Office of Public Health estimates that in Switzerland in summer, five minutes' exposure to the sun (from the face, arms and hands) is enough to cover daily requirements.

Vitamin D and bones

In the past, vitamin D was only known as the bone vitamin. In cases of severe and prolonged deficiency, bones become deformed. In recent years, research has discovered new effects. For example, sufficient vitamin D supports normal muscle function and immune metabolism. And this is where it becomes particularly interesting for sportspeople.

Vitamin D in sport

In the event of intense fatigue, people in sport today think not only of an iron deficiency, but also, precisely, a vitamin D deficiency. Nevertheless, too much of it can be deleterious for the metabolism and sporting performance. A low level of vitamin D normalised in the blood can give better results. As with all nutrients, too much is too much. Blood levels of 125 nanomoles per litre or more should be avoided, as negative health consequences such as kidney stones or arteriosclerosis cannot be ruled out. So refrain from taking supplements without regular blood tests by health specialists.

Low vitamin D levels are about as common in sport as in the general population. For example, according to estimates by the Federal Office of Public Health, around 50 per cent of people in Switzerland have levels below 75 nmol/l. According to a representative study from 2017, the situation is virtually identical among Swiss sportswomen: 50 per cent of those examined have vitamin D levels that are too low, below 75 nmol/l in the blood.

In summary

• Vitamin D is produced in the skin through exposure to sunlight; little is provided by diet.
• In summer, controlled exposure to the sun is very sensible; in winter, the sun is too weak for sufficient production of vitamin D.
• Less than 75 nmol/L of vitamin D in the blood is considered an insufficient level; around half of the Swiss population, sportsmen and women included, have a level below this target value.
• A blood test towards the end of autumn will show whether you produced enough vitamin D in the summer to get you through the winter.
• Only take vitamin D supplements to correct a deficiency in consultation with your health specialist.

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