Our content at a glance:

• What is vitamin D?
• What functions does vitamin D have?
• What are possible reasons for a deficiency?
• Do I need to supplement vitamin D?
• Which foods contain vitamin D?
• Overview of the most important facts about vitamin D

What is Vitamin D?

Vitamin D is a fat-soluble vitamin that occurs in two main forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). It is often referred to as the "sun vitamin" because your body is able to produce vitamin D itself under the influence of sunlight. This happens when UV-B rays hit your skin and trigger a reaction in which cholecalciferol is formed.

What functions does Vitamin D have?

Vitamin D is more than just a vitamin, it acts more like a hormone and has a variety of functions in your body. The most important functions include:

• Bone health
• Immune system
• Inflammation inhibition

Vitamin D plays a crucial role in the absorption of calcium and phosphorus in the intestine. These minerals are essential for strong bones and teeth. It also strengthens the immune system and helps your body to fight infections. The sunshine vitamin can also help to reduce inflammatory processes in your body, which is important for disease prevention.

What are possible reasons for a deficiency?

Vitamin D deficiency is a widespread problem, especially in regions with little sunlight and during the winter months. Reasons for a deficiency can include:

• Lack of sun exposure: If you spend little time outdoors, your body's own vitamin D production may be impaired. Half an hour in the sun in summer is enough to cover your daily vitamin D requirements. During the winter months (October to March), UV-B rays do not reach the earth's surface, which is why your body cannot produce vitamin D even on sunny days.
• Dark skin: People with dark skin have a natural barrier against UV rays and can therefore develop a deficiency more quickly.
• Age-related degradation: As you get older, your body's ability to produce vitamin D decreases.
• Poor diet: Inadequate intake of vitamin D-rich foods can also lead to a deficiency.

Do I need to supplement Vitamin D?

The need for vitamin D supplements depends on your individual lifestyle and health. If you are exposed to little sunlight or belong to a risk group for vitamin D deficiency, a supplement could be useful. However, you should always consult a doctor or nutritionist before taking supplements, as excessive intake of vitamin D can be harmful.

Your body can store vitamin D in fat and muscle tissue. If you top up your stores sufficiently over the summer months and continue to eat foods rich in vitamin D, this will be enough to provide you with sufficient vitamin D over the winter months. In spring, you can then recharge your empty stores with the help of natural sunlight.

Which foods contain Vitamin D?

Although vitamin D is found in food, natural sources are limited. Good sources are:

• Fish: Salmon, mackerel and tuna are rich in vitamin D
• Egg yolk: Eggs contain vitamin D, especially the yolk
• Mushrooms: Some types of mushrooms can produce ergocalciferol (vitamin D2) when exposed to UV light.
  Caution: However, most mushrooms are cultivated without daylight or with artificial light and therefore contain no vitamin D!
  Tip: Place your mushrooms under a UV-B lamp for 1-2 hours to increase their vitamin D content.
• Fortified foods: Many foods such as milk, muesli and juices are fortified with vitamin D.

The most important things at a glance

Tips on how you can get enough vitamin D.

Sunbathe: Top up your stores over the summer months

*Skin type I/II: light to very light skin colour, light red or blonde hair, blue or green eyes

*Skin type III: medium skin colour, dark hair, brown eyes

Food and its vitamin D content

Determine your vitamin D status

If you are not sure how well your body is supplied with vitamin D, have your status determined by a doctor before you start taking supplements.

Overall, vitamin D is an important vitamin that fulfils various key functions in the body. By eating a balanced diet and getting enough sun exposure, you can help ensure that your body is adequately supplied with this important nutrient.

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