Vitamin D deficiency causes: the most important questions and answers

Vitamin D Mangel Ursachen: Die wichtigsten Fragen und Antworten

Vitamin D is the only vitamin that can be absorbed by the body not only through food but also through exposure to the sun. That is why it is often referred to as the sun vitamin around the world.

Around 1 billion people worldwide suffer from a vitamin D deficiency due to various causes. In the following guide we explain what causes these are, what effects they have on the body and how you can best prevent these causes. With our help, you will get an effective overview of the most important values ​​and key data associated with vitamin D deficiency and its causes.

the essentials in brief

  • A lack of vitamin D can have long-term health consequences. The vitamin is present in every cell in our body and is particularly important for muscle and bone structure. Insufficient vitamin D supply can increase the risk of bone fractures or bone softening.
  • The main cause of vitamin D deficiency is mostly avoided exposure to the sun. Since 80 to 90 percent of vitamin D is absorbed through the skin through UV rays, you should expose yourself to sunlight every day.
  • There are several diseases and medications that can cause additional vitamin D deficiency. For example, medicines against the gastrointestinal tract and epilepsy are contributory causes of too little vitamin D.

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Causes of vitamin D deficiency: What you should know

Vitamin D plays an important role in everyday life, as many bodily processes are influenced by the vitamin. This includes processes in the bone and muscle area, as well as in our immune system. Vitamin D is considered to be particularly relevant for the metabolism of bones and calcium (1).

If the body lacks vitamin D, this can significantly damage our bone structure over a long period of time, since not enough calcium is stored in the bones (2).

What happens with a vitamin D deficiency?

Although the existence of vitamin D is well known, an estimated 1 billion people worldwide are vitamin D deficient. Studies have shown that more than 30 percent of the population in Germany is insufficiently supplied with vitamin D (3). According to official figures, in Switzerland it is up to 70 percent (4).

A constant value of 30 nanograms per milliliter of blood is recommended. According to medical guidelines, one speaks of a deficiency when less than 20 nanograms of vitamin D are present in the body per milliliter of blood (4.10">. If this deficiency is present, it can have long-term health consequences, since vitamin D is found in almost everyone cell of our body is present.

Animal foods

Unlike other vitamins, vitamin D is absorbed into the body through the sun's rays. Vitamin D is only found in animal foods such as fish or meat and even there only in small doses. (Image source: Jeremy Stewart / unsplash)

The most serious consequence of long-term vitamin D deficiency is possible decalcification of the bones, also known as osteoporosis or osteomalacia (4). The possibility of bone softening can increase from the critical value below 11 nanograms per milliliter (5.10">.

Among other things, an increased risk of the following diseases can be determined due to a critical vitamin D deficiency (7.8">:

  • cardiovascular diseases
  • Skeletal and muscular diseases
  • depression (15,16)
  • type 1 diabetes
  • type 2 diabetes
  • cancer (13,17)
  • Rheumatoid arthritis
  • Multiple sclerosis (MS)

This is accompanied by an increasing risk of falls and infections, as well as reduced fertility in women and a general increase in mortality (6.9">. Despite the observational studies that have been carried out, experts still disagree on the causality of the diseases mentioned in the list with vitamin D is really (10.11">. So far, only a negative effect on muscle and bone structure originating from vitamin D could be definitively determined. Therefore, a definitive risk assessment of vitamin D is not that easy.

In the case of an existing vitamin D deficiency, signs or symptoms appear rather insidiously, since they do not specifically indicate a vitamin D deficiency in the body.

How dangerous is a vitamin D deficiency?

Our body can produce 80 to 90 percent of the daily vitamin D it needs itself, as long as it can absorb enough sunlight through the skin. Especially in winter, the risk of a vitamin D deficiency is particularly high in our regions.

old couple

Especially in old age, a lack of vitamin D can have a negative impact on bone structure. The risk of bone fractures increases. (Image source: Cristina Gottardi / unsplash)

Vitamin D deficiency is dangerous at the already mentioned critical value of less than 11 nanograms per milliliter. However, a non-critical but long-term value below the recommended dosage can also have health disadvantages, which can be very dangerous in the case of osteoporosis or osteomalacia, as they have been shown to increase mortality (12.13">. Especially in older people, who suffer bone softening with associated fractures due to a lack of vitamin D, a deficit can be dangerous (14).

What are the signs of vitamin D deficiency?

With a vitamin D deficit, the symptoms can often appear insidiously. The most recognizable signs of acute vitamin D deficiency are as follows:

  • fatigue
  • Headache
  • bone pain
  • muscle weakness
  • sleep disorders
  • loss of appetite
  • Signs of depression (15,16)

These symptoms can also have other causes. Therefore, it can be difficult to identify a vitamin D deficiency based on the symptoms. Poor well-being and reduced maximum performance can indicate a vitamin D deficiency, but this is very unspecific.

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What are the most common causes of vitamin D deficiency?

The reason for vitamin D deficiency is often not getting enough sunlight. Vitamin D deficiency can occur more frequently, especially in people who often spend time in closed rooms. Clothing and sunscreen can also limit vitamin D absorption outdoors (14).

Sunscreen with a sun protection factor of 30 is up to 95 percent less effective at absorbing vitamin D (18).

Another cause often associated with a lack of UV exposure is a lifestyle that focuses more on indoors than outdoors. In addition, malnutrition and malnutrition can be partly to blame for a vitamin D deficiency, since the vitamin can also be ingested through food (19).

In addition, certain people/circumstances are more likely to develop a vitamin D deficiency:

  • Pregnancy : A vitamin D deficiency has been found in most pregnant women. Experts have found an increased need for calcidiol (a precursor hormone in vitamin D metabolism), which increases continuously until the end of pregnancy (22). From this it can be concluded that the necessary amount of vitamin D is above the normal average.
  • Age : The vitamin D absorption capacity of the skin decreases with advancing age. In addition, the absorbed vitamin D can no longer be converted effectively. Older people therefore produce up to 4 times less of the skin's own vitamin.
  • Infants : Newborns should not be exposed to direct sunlight. In combination with a low vitamin D content in breast milk, this can mean that infants are particularly susceptible to vitamin D deficiency.
  • Skin type : People with darker skin types produce less vitamin D in the body with the same amount of UV radiation.

If one of the causes on the list affects you or someone close to you, we can recommend that you have your vitamin D levels checked more closely. If there is a deficiency, supplements can be taken to compensate.

What diseases can cause vitamin D deficiency?

At the beginning we have already mentioned a list of possible diseases due to vitamin D deficiency. To a large extent it is not yet clear whether these diseases can serve not only as a consequence but also as a cause of vitamin D deficiency. Here the connections must first be researched in more detail (23).

encapsulate gastrointestinal

Gastrointestinal diseases can cause vitamin D deficiency. Gastrointestinal medications can also be a cause of the deficiency. (Image source: Christina Victoria Craft / unsplash)

A disease of the gastrointestinal tract can mean that less vitamin D can be absorbed. Likewise, taking the following medications can inhibit vitamin D absorption (21):

drug Description
antiepileptics Can help against epileptic seizures. More than 20 active ingredients are approved for medicines. Different drugs are used depending on the type of epilepsy and possible side effects for the user (24).
glucocorticoids Cortisone tablets which contain anti-inflammatory and anti-allergic substances. They are used in rheumatic diseases and autoimmune diseases (25).
antibiotics The goal of antibiotics is to kill or inhibit bacteria. In addition to possible vitamin D deficiency, antibiotics can cause a number of other side effects, such as dizziness, allergic reactions, and indigestion (26).
cholestyramine This drug is taken in powder form and is used to lower cholesterol levels in the blood. It acts mainly in the intestinal tract.
laxatives Cause irritation of the intestines and ensure liquefaction of the stool. Laxatives can be used before surgery or to treat hemorrhoids (27).

As you can see, some of the drugs listed can be used in the gastrointestinal tract. If you have diseases in this area, you should pay particular attention to an increased intake of vitamin D.

What can be done against acute vitamin D deficiency?

There are several ways to maintain adequate vitamin D levels. If there are no special conditions such as illness, pregnancy or the like, the intake of vitamin D through exposure to the sun is completely sufficient.

In winter, this type of vitamin D intake is less effective.

Experts recommend sun exposure three times a week. It is sufficient to expose hands, face and arms to UV radiation for 5 to 25 minutes (28). This is generally more difficult in winter due to less UV radiation (4). Below is an overview of the different ways you can get vitamin D:

kind Description
Natural recording The most common measure against vitamin D deficiency. In summer, one should expose the body to sunlight for 5 to 25 minutes. You can repeat this step up to three times a week.
food There are a variety of foods that contain vitamin D. This primarily includes foods of animal origin. Compared to vitamin D intake from direct sunlight, the vitamin D intake from food is relatively low.
Vitamin D supplements Alternatively, preparations in the form of prescription tablets or dietary supplements can be used. The preparations differ in the active ingredient and the dosage.

Some experts recommend this method during the winter months to compensate for the lack of sun exposure (3). However, we recommend that you do not take any supplements until you have had a blood test. This is how you prevent a possible overdose of vitamin D.

How can you prevent the causes of a vitamin D deficiency?

Since a lack of sun exposure is the main cause of vitamin D deficiency, going outside regularly can help prevent it. We recommend that you expose yourself to the sun several times a week from April to September. The required solar radiation can already be recorded on the way to work or school.

Girl stands in the sun

Vitamin D is most effectively absorbed into the skin through exposure to direct sunlight. Daily exposure to UV radiation is therefore the best way to prevent a deficiency. Image Source: (Jude Beck / unsplash)

It is best not to use sunscreen as it reduces vitamin D synthesis. If you have very light skin, a short exposure to UV rays is sufficient. This is how you avoid sunburn despite the lack of protection.

Which foods prevent vitamin D deficiency?

We only cover 10 to 20 percent of the vitamin D requirements in our body through nutrition. Since only a few foods contain vitamin D in small amounts, obtaining the vitamin from food is not the sole alternative to sun exposure. Nevertheless, we provide you with a clear overview of the different foods and their vitamin D dosage. Especially in the winter months, a nutrition plan adapted to vitamin D can definitely help to reduce the risk of a deficiency:

Groceries examples Vitamin D per 100 grams
Dairy products Emmental, Gouda, Fatty milk 0.3 to 3.1 micrograms
sea ​​animals Oysters, salmon, eel, sardine 8 to 25 micrograms
Meat chicken, lamb and beef 1.3 to 2 micrograms
Mushrooms Mushroom, chanterelle, morel 1.9 to 3.1 micrograms

For example, to get the recommended 20 micrograms of vitamin D from food, you would need to eat 5 pounds of mushrooms, 10 pounds of beef, or over 80 eggs per day (3). The main source of the vitamin is and remains sunlight.

What is the ideal vitamin D blood level?

The recommended blood level for enough vitamin D is 30 nanograms per milliliter of blood (4.10">. However, a level between 40 and 80 nanograms per milliliter is sometimes recommended.

If a deficiency is suspected or before taking vitamin D preparations, a blood test should be carried out. This allows the current vitamin D blood value to be determined precisely. You can have a vitamin D blood test carried out by your family doctor. Alternatively, vitamin D test kits can also be ordered online. This makes it possible to take a blood sample yourself and then send it to the specified laboratory.

How much does a vitamin D determination in the blood cost?

Checking vitamin D levels is not part of a normal medical check-up. The cost of a blood test is around 20 - 30 euros.

If the defect is confirmed, it is possible that the health insurance company will cover the full cost of the test. We recommend that you have a test done if you have the symptoms mentioned at the beginning and if you suspect a vitamin D deficiency. The test fee of 30 euros can pay off in the event of an acute deficiency, since the treatment of any vitamin D complications could become considerably more expensive.


Vitamin D deficiency can have various causes. In addition to the obvious lack of UV radiation, drugs and gastrointestinal diseases can also intensify the vitamin D deficiency. However, a lack of sunlight appears to be the most commonly cited cause of vitamin D deficiency.

We recommend that you expose your skin to the recommended dose of sunlight every day during the spring and summer months. During the winter months, you should make sure you eat a diet that is more concentrated in vitamin D, since in our region the UV intensity decreases significantly at this time.


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