Vitamin D in Deutschland: Sonnenstunden, Breitengrad und wie viel Sonne wir wirklich brauchen

Vitamin D ist essenziell für zahlreiche Stoffwechselvorgängen im Körper – dennoch ist ein Vitamin D Mangel in Deutschland weit verbreitet. Der Grund dafür liegt nicht nur im Lebensstil, sondern vor allem im Breitengrad und der Sonneneinstrahlung.

In diesem Artikel erfährst du, wie viele Sonnenstunden Deutschland hat, wie der Breitengrad die Vitamin D Bildung beeinflusst und wie viel Sonne du tatsächlich brauchst – basierend auf aktuellen wissenschaftlichen Informationen der Deutschen Gesellschaft für Ernährung (DGE) und internationalen Studien.

Hours of sunshine in Germany: How much sun is there really?

Germany has approximately 1,500 to 2,000 sunshine hours annually. Regions in the south often reach higher values than the north. However, the duration of sunshine varies greatly depending on the region and season.

However, for vitamin D synthesis, it's not the pure duration of sunshine that's crucial, but the UV radiation in the UVB range (290–315 nm) – and this strongly depends on the sun's position and its height above the horizon.¹

👉 Therefore:
Despite many hours of sunshine, vitamin D production is not possible all year round. Studies show that in Germany, UVB radiation is only sufficient for vitamin D production from March/April to October.²

Latitude and Vitamin D: Why Germany is at a Disadvantage

Germany is located between the 47th and 55th parallels of latitude. This geographical factor has a direct impact on vitamin D synthesis.³

The problem:
The further a country is from the equator, the lower the sun is in the sky – especially in winter. At a solar zenith angle of >45°, UV radiation is filtered so strongly by the atmosphere that hardly any vitamin D can be formed.⁴

Specifically, this means:

October to March: hardly any UVB radiation
Insufficient vitamin D production via the skin is possible
In Berlin (52° N), this "vitamin D winter" phase lasts about 6 months; in the south (47° N), it lasts about 4–5 months³

For comparison:

Countries near the equator: year-round vitamin D production
Southern Europe (e.g., Barcelona, 42° N): significantly longer periods with sufficient sun exposure

👉 Latitude is one of the most important factors for vitamin D status – this was confirmed in a comprehensive EU study of 46 cities over 18 years.¹

A study by Khanna et al. (2022) analyzed seasonal UV radiation variation in Europe and found: In high European latitudes (>52° N), the "vitamin D winter" lasts over 7 months, while in Southern Europe it is only <2 months. The data correlated strongly with seasonal fluctuations of 25(OH)D serum levels in the population.⁴

How does the body produce vitamin D through the skin?

Vitamin D production in the skin occurs through UV radiation, which converts 7-dehydrocholesterol (a precursor) in the skin into pre-vitamin D3. This is then converted in the liver to calcifediol and finally in the kidneys to calcitriol – the active hormone. ⁵

Vitamin D holds a special position among vitamins: It functions more like a hormone and regulates numerous genes via the Vitamin D receptor.⁶

For this process to function optimally, several factors are crucial:

Requirements for Vitamin D Production:

Sun exposure (optimally between 11 AM and 3 PM)
Sufficient uncovered skin (e.g., arms, face, head if bald)⁷
Direct sunlight (no glass!)⁷
Stay outdoors for at least 15–30 minutes⁷

Factors reducing education:

Sunscreen (SPF 15 reduces synthesis by ~99%)
Clothing
Staying behind glass (windows completely block UV radiation)
Air pollution
Darker skin type (requires 3–6× more time)⁷
Old age: Elderly people produce up to 75% less vitamin D⁸

How Long in the Sun for Vitamin D?

The question "How much sun do you need for vitamin D?" cannot be answered with a blanket statement, but there are clear guidelines based on skin type and season:⁷

Skin type

Recommended Duration (Summer, midday)

Skin type: Fair (Type I–II)

approx. 10–15 minutes

Medium (Type III)

approx. 15–25 minutes

Dark (Type IV–VI)

approx. 30–60 minutes

Important:

2–3 times a week is often enough⁷
Better regularly than rarely for long periods⁷
No sunburn – this damages the skin and increases the risk of skin cancer⁷
The sum of weekly exposure is more crucial than individual long sessions³

Note: Full-body exposure can generate up to 250 µg (10,000 IU) of vitamin D per day in summer – but only in the first 30 minutes, after which production flattens out. International Units (IU) are often used for dosage: 1 µg = 40 IU.³

Vitamin D Requirement: How Much Vitamin D Per Day?

If there is insufficient sunlight exposure, the recommended vitamin D intake is:

approx. 800 IU (20 µg) vitamin D per day for adults³
The German Nutrition Society (DGE) recommends this intake if endogenous production is insufficient.⁹

However, individual requirements may vary depending on:

Age (older people need more)
Body weight (vitamin D is fat-soluble and stored in fat tissue)
Skin type
Lifestyle (indoors vs. spending time outdoors)
Geographic location (Germany: 47–55° N)¹⁰

Vitamin D Suppliers: Nutrition and Food

The intake via food is limited, as only a few foods contain significant amounts:³

Natural sources of vitamin D:

Fatty fish (salmon, herring, mackerel): 10–25 µg per serving
Egg yolk: 2–5 µg
Mushrooms (only after UV irradiation): variable
Fortified foods (rare in Germany)³

Through diet alone, only approx. 2–4 µg per day can be absorbed – far below the required amount. The sum of sunlight exposure and food is not sufficient in Germany in winter.

Why Vitamin D is so Important: Bones, Muscles, and More

Vitamin D contributes to

normal absorption | utilization of calcium and phosphorus in
a normal blood calcium level in
normal blood clotting in
maintaining normal muscle function in
maintaining normal bones in
normal immune system function in

Calcitriol (the active form of vitamin D) acts in the intestine to increase the absorption of calcium and phosphate.⁷

Why Vitamin D Deficiency is So Common in Germany

A vitamin D deficiency in Germany arises from the interplay of several factors: ¹¹

High latitude (47–55° N) → long winters without UV radiation¹¹
Long winter period without sufficient sunlight ¹¹
Predominantly indoor lifestyle (office, school, home office) – too little time spent outdoors¹¹
Use of sunscreen (important for skin cancer prevention, but blocks UV radiation)⁷
Air pollution (additionally filters UV radiation)¹¹
Elderly people: reduced production in the skin and lower mobility⁸

👉 Even in summer, too little time is often spent in the sun to adequately replenish stores.¹¹

Latest Data: Vitamin D Status in Germany

According to the Robert Koch Institute (RKI) and the German Nutrition Society:

30.2% of adults have a vitamin D deficiency (<50 nmol/l)
In winter, this figure is even >50%
Among older people (women over 65), the rate is 75% – even in summer⁸
The average value is 55–60 nmol/l in summer, but only 30–40 nmol/l in winter⁹

Risk groups for vitamin D deficiency:

Older people (>65 years)
People with dark skin types
Individuals who spend little time outdoors (office workers, nursing home residents)
Overweight individuals (vitamin D is stored in fat tissue)⁸
People with chronic liver or kidney diseases³

Study Result:
A representative study of over 4,000 German adults showed: 57% of men and 58% of women had 25(OH)D values below 50 nmol/l. Independent predictors for low values were: winter, low physical activity, high BMI, and low socioeconomic status.⁹

Conclusion: Latitude determines your vitamin D supply

While Germany has many hours of sunshine, it does not have enough UV radiation in winter²
The latitude (47°–55°) limits the body's own vitamin D production to approximately 6–7 months per year ¹
Regular sun exposure in summer is crucial to fill up stores⁷
In winter, vitamin D supply should be consciously considered through diet or vitamin D supplements⁴
Risk groups (e.g., elderly people, dark skin types, spending little time outdoors) should have their vitamin D status checked⁸

👉 In short:
It's not just the sun that matters – but when, where and how it hits your skin. In case of insufficient sun exposure, vitamin D tablets or other food supplements are a sensible option for an adequate vitamin D supply.⁷

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