Vitamin D deficiency

In winter in particular, many people in Germany do not get enough vitamin D. This is important for the bones and other metabolic processes in the body. This article provides an overview of the risk factors and symptoms of a vitamin D deficiency, as well as how it can be prevented and treated.

At a glance

  • Vitamin D is the collective name for calciferols, a group of fat-soluble vitamins.
  • The human body produces vitamin D in sunlight.
  • Fatty fish, offal, eggs, edible mushrooms and cod liver oil all contain vitamin D.
  • Vitamin D is important for bone metabolism.
  • A vitamin D deficiency leads to bone conditions such as rickets in children and osteomalacia in adults.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Vitamin D deficiency: young woman in a forest with the sun shining on her face. Her eyes are closed, she looks relaxed.

What is a vitamin D deficiency?

The human body needs a number of substances that it cannot or not sufficiently produce itself. Vitamins are one such example. One group of these are the calciferols, otherwise known as vitamin D.

People can only produce these substances when directly exposed to UV-B radiation from the sun. This means that in northern regions, people often have a lack of vitamin D in the winter months – between about October and April. 

If the body has a vitamin D deficiency, it is unable to absorb calcium from food, leading to the decalcification and ultimately the softening of the bones.

If infants receive too little vitamin D in the first few months of their lives, their bones bend and their wrists swell. This is known as rickets. However, this condition can also have other causes, including a phosphate deficiency or genetic causes.

Important: Vitamin D deficiency exists if insufficient vitamin D is found in the body over a prolonged period and clinically relevant symptoms present themselves. The vitamin D status is determined by measuring a precursor of the active vitamin D in the blood. Depending on the test method, several different values are produced. Rapid tests from pharmacies are therefore not suitable for reliably diagnosing a vitamin D deficiency.

What is vitamin D and why is it important?

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What are the symptoms of vitamin D deficiency?

Doctors diagnose a vitamin D deficiency if people have not been supplied with vitamin D for such a long time that they have some of the following symptoms:

  • bone pain
  • bone deformation, especially of the ribs, legs and spine
  • bone fractures
  • swelling where cartilage meets the bones
  • softening of the back of the head
  • retarded closing of the fontanelles in infants
  • muscle weakness
  • vulnerability to infections

What are the risk factors for a vitamin D deficiency?

People who spend little time outdoors have a higher risk of vitamin D deficiency. This particularly applies to people who are immobile, in need of care and very elderly as well as people with dark skin and who cover themselves up when outdoors for cultural or religious reasons. Even people who live or work in bright rooms can be affected as window panes block UV radiation. 

Certain medical conditions such as malnutrition, chronic inflammatory bowel disorders, osteoporosis or rheumatoid arthritis also increase the risk of a vitamin D deficiency.

How can vitamin D deficiency be prevented?

To get enough vitamin D, the German Nutrition Society (DGE) recommends exposing the face, hands and parts of the arms and legs to the sun for 5 to 25 minutes per day – depending on the skin type and time of year – between 12 p.m and 3 p.m. The suggested period should be doubled in the morning between 10 a.m. and 12 p.m. and in the afternoon between 3 p.m and 6 p.m.

You should spend 5 to 25 minutes outdoors every day to ensure you get enough vitamin D.

Unlike in the summer months, the sun’s radiation in Germany from October to March is not strong enough to ensure that the body produces enough vitamin D. However, the body can make up for this by storing larger amounts of vitamin D in spring and summer.

Vitamin D can also be absorbed from food. It is primarily found in fatty saltwater fish, offal like liver and kidneys, edible mushrooms and eggs. Cod liver oil also contains high levels of vitamin D. It should, however, be noted that food only supplies supplemental vitamin D; it cannot provide enough vitamin D on its own.

In Germany, infants in their first few months of life are given vitamin D to prevent deficiencies.

Vitamin D supplements are only recommended if an insufficiency has been detected that cannot be rectified through sunlight and diet. Elderly people living in care homes, for instance, should receive 20 micrograms of vitamin D per day as a food supplement.

Important: Taking over 100 micrograms of vitamin D per day in tablet or drop form for a prolonged period can lead to an oversupply. This presents a risk of undesirable side effects as the heart, kidneys, blood vessels or liver can be increasingly affected by calcium deposits. This can result in headaches, vomiting, drowsiness, diarrhea and excessive urinary urgency. Excessive sunshine does not lead to oversupply.

How is vitamin D deficiency diagnosed?

There are several diagnostic procedures available to doctors if they suspect a vitamin D deficiency. These include:

  • asking about typical symptoms, habits such as diet and exercise in the fresh air, taking medication, family history
  • a physical examination
  • blood tests
  • for children, an X-ray of the hand to detect possible joint deformation

How is vitamin D deficiency treated?

A proven vitamin D deficiency that cannot be rectified through sunlight and diet is treated with tablets. Patients are usually also given calcium.

Further information

Do you want to know exactly what doctors class as a vitamin D deficiency or have other questions about vitamin D? Answers to frequently asked questions can be found on the Robert Koch Institute website.

Reviewed by the German Nutrition Society (Deutsche Gesellschaft für Ernährung e.V. – DGE).

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