Vitamin D – the sunshine vitamin

Vitamin and mineral lexicon

Vitamin D occupies a special position among the vitamins. Because our body can produce the fat-soluble vitamin itself in the skin. To do this, it depends on sufficient sunlight, or more precisely UVB rays. But the body’s own production of vitamin D varies from person to person and depends on factors such as the season or skin type. Anyone who regularly spends time outdoors, especially in the summer months, can cover a large part (up to 80-90 percent) of their vitamin D supply through their own body production. However, if the sun’s rays are not strong enough, the sun is avoided for various reasons or the body’s ability to produce the sun vitamin is reduced, the importance of vitamin D intake through the diet or as a dietary supplement increases.

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How can a vitamin D deficiency occur?

In the months from October to March, solar radiation in Germany is usually not strong enough to ensure sufficient vitamin D production, so the body relies on existing vitamin D stores. In addition to the time of year and day, there are also other factors that influence the body’s production of vitamin D:

  • weather

  • Place of residence,latitude

  • Length of stay outdoors

  • Increased age

  • Darker skin types

  • Skin-covering clothing

  • Use of sunscreen

Risk groups for vitamin D deficiency

Therefore, the contribution of the body’s own production to the vitamin D supply can vary greatly from person to person. The risk groups for undersupply include people who spend little or no time outdoors or are unable to do so – such as people with limited mobility, people who are chronically ill and in need of care, or even older people. In the latter case, the skin’s ability to produce vitamin D becomes increasingly difficult as we get older. Compared to younger age, this ability is sometimes reduced to less than half. In addition, people with dark skin type are among the risk groups. Due to the higher content of the pigment melanin in the skin, vitamin D production is lower. In order to produce the same amount of vitamin D, people with darker skin types have to spend longer in the sun. Another risk group are people who only go outside fully clothed – be it for cultural or religious reasons. All of these living conditions can promote an undersupply of vitamin D and make additional intake useful.

Risk groups:

  • People who are rarely outside
  • Older people
  • People with dark skin type
  • People who only go outside fully clothed

Symptoms of a vitamin D deficiency – consequences of undersupply

The exact definition of a vitamin D deficiency is still being debated. However, it is known that almost 60 percent of the federal population do not achieve the desirable vitamin D stores (blood concentration of 25-hydroxyvitamin D of ≥ 50 nanomoles per liter or ≥ 20 nanograms per milliliter). For example, many citizens cannot take advantage of the preventative potential of vitamin D for bone health – reducing the risk of falls and bone fractures – because they are not adequately supplied with it. If there is a significant vitamin D deficiency, this can manifest itself in disorders of bone metabolism and symptoms such as reduced muscle strength and increased susceptibility to infections.

Vegetarian or vegan diet and vitamin D

Vitamin D occupies a special position among the vitamins. Because our body can produce the fat-soluble vitamin itself in the skin. To do this, it depends on sufficient sunlight, or more precisely UVB rays. But the body’s own production of vitamin D varies from person to person and depends on factors such as the season or skin type. Anyone who regularly spends time outdoors, especially in the summer months, can cover a large part (up to 80-90 percent) of their vitamin D supply through their own body production. However, if the sun’s rays are not strong enough, the sun is avoided for various reasons or the body’s ability to produce the sun vitamin is reduced, the importance of vitamin D intake through the diet or as a dietary supplement increases.

Piece of advice

But be careful! Anyone who is exposed to the sun unprotected too much and for too long must expect an increased risk of skin cancer. According to the German Cancer Aid, intensive sun exposure at midday in summer is not recommended. But that doesn’t mean that the sun should necessarily be avoided. During longer stays and activities outdoors, appropriate sun protection measures (sunscreen, hat, etc.) should be taken.

Forms of vitamin D and functions in the body

Forms: 

The most important forms of vitamin D are D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D2 is formed, among other things, in plants and fungi from the precursor ergosterol or ergosterol, which is found there in trace amounts. Vitamin D3 is the form that the body can produce in the skin from the precursor cholesterol or cholesterol with the help of the sun’s rays. This form also occurs in some foods, especially animal foods. Vitamin D2 and vitamin D3 differ only minimally and are subject to the same metabolic pathway – both are first converted by the body into a storage form and then converted into the active form.

Function:

In the body, vitamin D promotes the absorption of calcium and phosphate from the intestine and their storage in the bones and teeth, and contributes to normal bone metabolism. Vitamin D is also involved in muscle function, the immune system and other metabolic processes. Its numerous functions make the vitamin the subject of current research.

Sources of vitamin D – where is vitamin D in it?

In order for the body to produce vitamin D, sufficient skin surface area (approx. a quarter of the body surface area – such as the face, hands and a large part of the arms and legs) must be exposed to the sun. Depending on the sun intensity and skin type, around 5-25 minutes per day is recommended. The German Society for Nutrition recommends vitamin D intake through your diet. V. (DGE) for children, adolescents and adults 20 micrograms (µg) of vitamin D per day – if the body’s own vitamin D production is insufficient or missing. But only a few foods contain significant amounts of the vitamin. Good sources are fatty sea fish such as salmon, herring and mackerel. To a much lesser extent, liver, margarine enriched with vitamin D, egg yolk and some edible mushrooms are also included. On average, only 2-4 micrograms of vitamin D are absorbed per day through the foods that are common in Germany. If there is no or too little self-production or insufficient intake through the diet, supplementary intake of vitamin D can be useful.

*1 IU = 0.025 μg vitamin D; 1 μg vitamin D = 40 international units (IU)