June 22, 2026, 8:11 am | Read time: 5 minutes
“Take vitamin D? I don’t need to, I’m outside so much!” I’ve heard that many times. And I used to say it myself. But the reality is different. Here are my reasons as a nutritionist for taking vitamin D even in the summer—and why you might want to consider it too.
Vitamin D Can Do Something Other Vitamins Can’t
Vitamin D is unique among vitamins: While other vitamins must be regularly obtained through diet, our bodies can produce vitamin D on their own. This requires UVB radiation to hit the skin. That’s why vitamin D is often called the “sunshine vitamin.”1
In the body, vitamin D ensures strong bones and teeth, influences muscle strength, and is involved in other metabolic processes, including immune function. Especially in older adults, good vitamin D levels can reduce falls and fractures. For chronic diseases, no clear benefit has been proven: Observational studies link low vitamin D levels to a higher risk of cancer, cardiovascular diseases, type 2 diabetes, and other illnesses. However, this doesn’t mean vitamin D offers protection.2,3
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What Is the Supply Situation in Germany?
The supply situation in Germany is not as good as many assume: 30.2 percent of adults have a vitamin D deficiency.4 According to the German Nutrition Society (DGE), about 60 percent of the population also has insufficient vitamin D levels. This means their blood marker 25-hydroxyvitamin D is below the optimal value of 50 nanomoles per liter. This doesn’t necessarily indicate a deficiency, but it shows that many people are not taking full advantage of vitamin D’s preventive potential, especially for bone health.5
In the absence of self-production, the DGE estimates a daily requirement of 20 micrograms of vitamin D. However, through a typical diet, teenagers and adults in Germany only consume about two to four micrograms daily. Food alone can hardly fill the gap. Foods relatively rich in vitamin D include:
- Salmon (16 micrograms of vitamin D per 100 grams)
- Egg yolk (5.9 micrograms of vitamin D per 100 grams)
- Chanterelles (2.1 micrograms of vitamin D per 100 grams)
Diet plays only a minor role in vitamin D supply. Most of it must come from the body’s own production in the skin (or a supplement). This requires UVB radiation—and in Germany, it’s not strong enough year-round. From October to March, according to the DGE, sunlight is generally insufficient to produce enough vitamin D.
But I’m in the Sun a Lot!
Many people think this way. As a rough guide, in the warm season, just five to 25 minutes of sun exposure several times a week is enough if the face, hands, and parts of the arms and legs are uncovered.6 Sounds easy to implement. So, no need for a supplement, right? It’s not that simple. The body’s vitamin D production is individual and depends on many factors:
- Limited time outdoors: Those who spend most of the day (especially the UVB-rich midday) indoors, such as in an office, receive little UVB radiation on their skin. Vitamin D production doesn’t work behind window glass.
- Covering clothing: The more skin is covered, the less vitamin D can be produced. This includes long pants and sleeves, head coverings, or fully covering garments like burqas or niqabs.
- Darker skin type: More melanin acts as a natural UV protection. People with darker skin produce vitamin D more slowly with the same sun exposure.
- Sunscreen: Sunscreen reduces UVB radiation on the skin. However, it remains important for skin cancer prevention.
- Older age: As age increases, the skin’s ability to produce vitamin D decreases. This is particularly relevant for older, mobility-impaired, or care-dependent individuals.
- Unfavorable time of day, shade, and weather: In the morning, evening, with heavy cloud cover, or in the shade, less UVB radiation reaches the skin. Air pollution can also reduce sunlight.
- Vegetarian or vegan diet: These diets don’t inhibit skin production but can further limit intake from food, as significant amounts of vitamin D are primarily found in animal products.
In short, just because it’s summer doesn’t mean our bodies produce enough vitamin D. That’s why it can be wise to have your vitamin D status checked—and, if necessary, consider a supplement even in summer. Many nutrition experts already do this. At the Life Summit 2026, Dr. Luisa Werner and nutritionist Sophie Chabloz shared that they regularly take the sunshine vitamin. “Even in summer, many people don’t reach optimal levels,” Chabloz said.