Vitamin D deficiency

A vitamin D deficiency exists if insufficient vitamin D is found in the body over a prolonged period and symptoms appear that require treatment.

A differentiation should be made from an insufficient supply of vitamin D, where the amount of vitamin D in the body is reduced but the person has no symptoms.

What is vitamin D?

Vitamin D is the umbrella term for various fat-soluble vitamin D compounds, which are also known as calciferols. The active form of vitamin D in the body is called calcitriol.

The two most important precursors are:

• Vitamin D2 (ergocalciferol)
• Vitamin D3 (cholecalciferol)

Humans primarily require vitamin D to develop healthy bones. Vitamin D helps the body absorb calcium from the intestines and incorporate it into the bones. This makes them strong and stable.

Vitamin D is also involved in other metabolic processes in the body. For example, it influences muscle strength and is important for the immune system.

How is vitamin D formed?

Vitamin D is formed from its precursors in several steps. These involve the skin, the liver and the kidneys. The body can independently produce most of the vitamin D it requires if the skin is directly exposed to the UVB radiation produced by sunlight. This can be achieved by spending time outdoors. 

The actual amount of vitamin D produced in the skin as a result of sunlight depends on various factors. These include the latitude, the time of year, the time of day and the weather. A person’s skin type, clothing and the use of sunscreen also have an influence. As a result, the amount of time that people need to spend outdoors for the body to produce enough vitamin D can vary significantly.

In addition to the body’s natural production of vitamin D, small amounts of the vitamin can also be absorbed from food. The body can also store a certain amount of vitamin D during the spring and summer so that it already has sufficient supplies for less sunny periods such as winter.

Even if people do not have enough vitamin D in their body for a long time, they will not necessarily develop any symptoms of this.

An actual vitamin D deficiency, on the other hand, is associated with various symptoms. Many symptoms are caused by problems with the bone metabolism. These result in the bones becoming “decalcified” and therefore losing stability.

Symptoms in children

If children have a vitamin D deficiency, this can severely impair bone growth and cause permanent skeletal deformities. This is known as rickets.

The main symptoms of a vitamin D deficiency in children include:

• bone deformation, especially of the spine, ribs and legs
• swelling where cartilage meets the bones
• softening of the back of the head and retarded closing of the fontanelles in infants
• muscle weakness with problems standing and walking
• delayed motor development
• seizures
• increased susceptibility to infection

Symptoms in adults

In adults, the decalcification of bones can result in osteomalacia. This is the term used by medical practitioners for a condition characterized by soft bones, bone pain and muscle weakness.

A vitamin D deficiency also increases the risk of developing osteoporosis (bone atrophy), especially in older people.

A vitamin D deficiency in adults can manifest itself through the following symptoms:

• Bone and limb pain
• Muscle weakness, muscle pain and muscle twitches
• Falls and broken bones
• Tiredness and rapid exhaustion (fatigue)

The body is able to naturally produce most of the vitamin D that it requires. To do this, however, the skin has to come into regular contact with sunlight. People who spend little time outdoors are therefore at greater risk of not having enough vitamin D.

In this context, certain groups of people are at particularly high risk of developing a vitamin D deficiency. These include:

• people who have restricted mobility or chronic illnesses or who are in need of care and spend little time outdoors
• elderly people: as we age, our body’s natural production of vitamin D wanes.
• infants: their skin is still extremely sensitive and should be protected against direct sunlight.
• people who always remain covered when outdoors for cultural or religious reasons
• people with a dark skin color: they need to remain in the sun for longer than people with light-colored skin to meet their vitamin D needs. This can be problematic due to the number of hours of sunshine in northern and central Europe.

Certain medical conditions also increase the risk of a vitamin D deficiency. These include chronic gastrointestinal diseases, chronic kidney diseases and liver diseases such as cirrhosis of the liver. Some medication can also lead to a vitamin D deficiency. This primarily includes epilepsy medication and chemotherapy medication.

The following actions are recommended to get enough vitamin D:

• Expose the face, hands and arms to the sun without any sunscreen two to three times per week
• The length of exposure to the sun should be half the time it would usually take to get sunburned when not using sunscreen
• The specific amount of time depends on factors such as skin type, time of year and time of day. For example, people with light-colored skin should expose this to sunlight for between 5 and 60 minutes per day from March to October

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. The body can make up for this by storing larger amounts of vitamin D in spring and summer, providing it has produced enough.

To a low extent, vitamin D can be absorbed from food. For example, it is found in oily saltwater fish, offal, mushrooms and eggs. However, people cannot meet their vitamin D needs through food alone. 

Prevention using vitamin D supplements

Vitamin D supplements should generally only be taken if an insufficiency has been detected that cannot be rectified through sunlight and diet. A dietary supplement is also recommended for people in certain at-risk groups.

In Germany, for example, the advice is to administer a vitamin D supplement to infants until their second early summer in order to prevent deficiency. The recommended daily dose of vitamin D is 10 to 12.5 micrograms, which equates to 400 to 500 international units (IU). Different recommendations apply to premature babies and chronically ill children. A pediatrician will provide personalized advice in such cases.

For people in other high-risk groups, a dietary supplement of 20 micrograms (800 IU) of vitamin D per day is recommended. This particularly includes people who are chronically ill, in need of care or extremely elderly.

Whether and to what extent a dietary supplement with vitamin D is required should best be discussed with a family doctor.

If doctors suspect a vitamin D deficiency, there are several diagnostic procedures available to them. They start by asking about typical symptoms and risk factors as well as conducting a physical examination. A blood test will then be used to determine the vitamin D status and other blood values in a laboratory. X-rays can be used to detect potential changes to the bones.

How is the vitamin D status determined and assessed?

The vitamin D status is determined by measuring the amount of 25-hydroxy vitamin D3 in the blood. 25-hydroxy vitamin D3 is a precursor to active vitamin D3 and is also known as calcidiol. 

The amount in the blood is specified as a serum concentration in nanomoles per liter (nmol/l) or nanograms per milliliter (ng/ml).

The vitamin D supply is assessed as follows in line with internationally recognized criteria:

• Values over 50 nmol/l or 20 ng/ml: sufficient supply to maintain bone health
• Values between 30 and 50 nmol/l or 12 and 20 ng/ml: restricted supply with potential consequences for bone health
• Values below 30 nmol/l or 12 ng/ml: deficient supply with heightened risk of illnesses such as rickets, osteomalacia and osteoporosis

How useful are vitamin D rapid tests?

Pharmacies and drugstores sell rapid tests for home use that people can use to independently determine their vitamin D status. However, these tests are not very reliable. Experts therefore advise against using them.

A proven vitamin D deficiency that cannot be rectified through sunlight and diet is treated with vitamin D supplements. These are generally in the form of vitamin D3.

The precise dose depends on several factors including the severity of the deficiency and the existing risk factors. In some cases, doctors will also prescribe calcium.

Regular follow-up tests are recommended so the dose of the vitamin supplement can be adjusted as required. This particularly applies to high dosage products, so as to avoid an overdose, which can have severe consequences.

Further information about vitamin D and when it is useful to take vitamin D supplements can be found at klartext-nahrungsergaenzung.de – a site provided by the customer advice centers.