Even if every day gives us a few minutes more light, it is still the time of year when we rarely see the sun – and therefore produce less vitamin D. Is this a problem? Seven questions and answers about the so-called sunshine vitamin.
Why does the body need vitamin D?
One thing first: When we talk about vitamin D, we are not talking about a single vitamin, but about a whole group of vitamins. The most important forms: D2 and D3.
Our body needs vitamin D, among other things, for the stability of our bones, as Daniela Krehl, nutrition expert at the Bavarian Consumer Center, explains. Vitamin D ensures that the body can absorb calcium from the gastrointestinal tract and incorporate it into the bones. Our body also needs vitamin D for muscle function and hormone metabolism, as well as for immune defense.
Where do we get vitamin D?
“Usually a vitamin is a nutrient that we consume through food,” says Daniela Krehl. However, things are a little different with vitamin D. There are foods that provide us with it, such as fatty sea fish such as salmon and mackerel, vegetable oils and dairy products.
“But this cannot cover the need,” says Prof. Johannes Wechsler, President of the Federal Association of German Nutritional Medicine Doctors. We only get around ten percent of what we need through food.
The body produces the rest itself, but for this it needs sunlight that hits the skin. More precisely: the sun’s UV-B radiation. Exactly how much vitamin D a body can produce in this way depends on many factors. About the time of year, latitude, time of day and skin type.
Whether we have applied sunscreen to protect ourselves from UV rays also has an impact – after all, spending time in the sun increases the risk of skin cancer. “If you apply a high sun protection factor or don’t go out in the sun at all, then you block the formation of vitamin D,” says nutritionist Wechsler.
So how intensively should we expose ourselves to the sun in order to produce enough vitamin D but not to run an unnecessary risk of skin cancer? Several specialist societies and research institutions have developed an answer to this question.
Her recommendation is: To produce enough vitamin D, it is enough to expose your face, hands and arms to the sun uncovered and without sunscreen two to three times a week. For half the time that you would otherwise get sunburned without protection. An example: For a person with a fairly light skin type, that would be around 12 minutes on a summer day with a UV index of 7.
Is that enough in winter too?
Between October and March there is not enough solar radiation in Germany for the body to produce enough vitamin D. “But since it is a fat-soluble vitamin, we can store it well,” says Daniela Krehl. These reserves in our fat and muscle tissue help us through the winter. But are they enough?
According to the German Nutrition Society (DGE), the majority of the population is not affected by a vitamin D deficiency. But almost 60 percent of Germans do not have the desired concentration in their blood. This is not (yet) a deficiency that leads to soft bones – osteomalacia. But there is not enough vitamin D in the body to achieve optimal prevention for bone health.
Who is at increased risk of actually developing a deficiency?
People who get little sunlight are at risk of vitamin D deficiency. “For example, people who are bedridden or people who cover themselves completely,” says Daniela Krehl.
Also: babies. Since infants should not go out in the sun unprotected and breast milk contains hardly any vitamin D, children should receive the vitamin in the form of tablets or drops in the first year of life. Parents are informed about this during the U2 check-up, which takes place in the days after the birth.
As we get older, the body produces less vitamin D, and even then a deficiency is more likely to occur. Obesity, i.e. being very overweight, can also mean that the body is poorly nourished. “This is probably because vitamin D is stored in fatty tissue – and is very strongly bound there,” says Daniela Krehl.
So should I take vitamin D supplements?
There is no one answer that applies equally to all people. For anyone who actually has an increased risk of a deficiency, it makes sense to have their vitamin D levels checked regularly by a doctor – and to take countermeasures.
And for everyone else? You can plan to bring the topic with you to your next doctor’s appointment and discuss it. Then you are on the safe side.
And take vitamin D supplements on your own? Nutritional doctor Johannes Wechsler thinks that this can definitely make sense. Prerequisite: Pay close attention to the dosage, which is given in international units (IU) or micrograms.
He recommends a dosage of 1000 international units “all year round, regardless of vitamin D levels. And it makes sense to have the level checked occasionally to see that this is actually helping.” Background: Disturbances in the gastrointestinal tract can mean that the body cannot absorb vitamin D as well – that can discovered during such checks.
The Federal Institute for Risk Assessment (BfR) is more cautious: “If you want to supplement vitamin D, you can use dietary supplements with up to 20 micrograms of vitamin D per daily dose,” the authority said in a statement. This corresponds to 800 international units.
Can I also take more vitamin D – according to the motto “A lot helps a lot”?
Better not. “With pure sunlight and a diet that is very rich in vitamin D, an oversupply cannot occur,” says Daniela Krehl. The situation is different with high-dose dietary supplements.
Anyone who takes them long-term risks hypercalcemia. During this process, more calcium is pulled out of the bones so that it is then found in the blood. The result: nausea and headaches, and in the long term there is a risk of kidney damage.
According to the BfR, high-dose vitamin D preparations should therefore only be taken under medical supervision. The authority refers to studies that have shown that a daily intake of just 100 micrograms or 4,000 international units permanently reduces bone density in older women.
Can’t I just go to the solarium to get my vitamin D needs?
This is not a good idea – especially because of the risk of skin cancer that every visit to a solarium increases. In addition, the UV radiation from modern solariums usually contains little or no UV-B radiation, as the BfS writes. So there are lower-risk ways to protect yourself from a vitamin D deficiency.