Vitamin D - Small molecule, big influence

The sun's warming rays are not only vital for plants. Our bodies wouldn't function without them either. No, we don't perform photosynthesis in some strange way. Rather, it's about the production of the vital substance... Vitamin D, which is involved in several metabolic processes.

It's all the more alarming that many people in this country suffer from a deficiency, especially during the colder months. Below you'll learn what our bodies need this vitamin for, how to recognize a deficiency, and what you can do about it.

How does the body supply itself with vitamin D?

We humans obtain almost all the nutrients we need through our food, or we can even produce them ourselves from other nutrients. Strictly speaking, this also applies to the production of vitamin D, which our bodies can synthesize from precursors of the vitamin. However, sufficient sunlight is necessary for this process to function.

We cover roughly 80-90 percent of our vitamin D needs through sunlight, which is converted into the precursor provitamin D3 in our skin through various metabolic processes. Our bodies then produce the actual vitamin D from this in the liver and kidneys. We cover the small remaining gap, which is usually around 10-20 percent, through foods containing vitamin D.

Why and what does our body need this vitamin for?

The active form of vitamin D is involved in a whole range of metabolic processes in the body and thus performs numerous functions. Among other things, the vitamin is involved in regulating the calcium concentration in the blood, bones, and intestines.

Doctors recognized early on that this vitamin is important for tooth and bone structure. A deficiency can lead to bone softening and osteoporosis. Furthermore, the vitamin fulfills other functions, including:

• Strengthening the muscles
• Positive effect on the health of the cardiovascular system
• Strengthening the immune system by inhibiting excessive immune responses and the defense against pathogens.
• Can reduce the risk of vascular disease
• It protects nerve cells, including those in the brain.
• Potentially positive influence on the psyche (e.g., counteracting depressive moods or winter depression)

Important: Many of these effects are not yet fully understood.

Many people suffer from a vitamin deficiency.

The fact that vitamin D is primarily produced through the sun's UV radiation is a major problem, especially in Central and Northern Europe. Due to the reduced duration and intensity of sunshine during the colder months, we are able to produce less provitamin D3 in our skin than in summer.

The effect is particularly dramatic for people who already spend most of the day indoors. Even though our bodies have a high storage capacity and essentially build up reserves for winter over the summer, these are insufficient for many people.

According to medical estimates, almost every second German suffers from at least a mild vitamin D deficiency for the reasons mentioned. A deficiency is diagnosed when the serum level is below 12 ng/ml of blood. You can easily find out if you have a deficiency by having your doctor perform a comprehensive blood test. Several factors increase the risk of a deficiency:

Risk groups and risk factors for a deficiency

• Air pollution, which absorbs some of the UV radiation from the air
• Excessive use of sunscreens
• A diet low in vitamin D (e.g., a vegan lifestyle)
• Spending too much time indoors
• People with dark skin need significantly more UV radiation to produce sufficient provitamin D3.
• The skin's ability to absorb moisture decreases with age.
• Poor health of kidneys, liver, or intestines
• Obesity, as too much body fat can inhibit the absorption of the vitamin.
• Women during pregnancy and breastfeeding
• Babies who are breastfed, as breast milk contains very little vitamin D.

Possible symptoms and consequences of a vitamin D deficiency
A vitamin D deficiency has profound consequences for our bodies, as numerous processes no longer function optimally. Before serious damage occurs, such as to teeth and bone structure, the immune system, for example, suffers from a deficiency. Increased susceptibility to infections is one of the main symptoms. Other possible signs include:

• Muscle and joint pain
• Muscle weakness
• Hair loss (e.g., circular hair loss)
• Abnormal sensations in lips and fingers due to calcium deficiency
• Bone pain, bone deformities
• Bone mineralization disorders (e.g., osteomalacia in adults, rickets in children)
• Depression (especially winter depression)

This is how you ensure an adequate supply of vitamins.

According to official information from the Robert Koch Institute, significant amounts of vitamin D can only be produced in Germany between March and October. To ensure adequate intake during the darker months, experts at the Robert Koch Institute recommend spending plenty of time outdoors – especially when the sun is shining.

Important: You should keep your hands, face, and arms uncovered as much as possible. It's also advisable to increase your intake of vitamin D through foods rich in vitamin D. These include fatty fish (e.g., salmon, tuna, mackerel, cod), liver, milk, eggs, sprouts, oatmeal, porcini mushrooms, and sweet potatoes.

Are dietary supplements useful?

Since the number of foods rich in vitamin D is limited, supplementation can be beneficial. This is especially true if you follow a vegetarian or vegan diet.

Since a sustained overdose of this fat-soluble vitamin can lead to symptoms of poisoning, it is advisable to discuss your individual dosage with your doctor beforehand. Ultimately, however, if the deficiency cannot be corrected through sunlight and a proper diet, dietary supplements are very useful.