The sunshine vitamin for hormone balance, immune system & energy
Vitamin D is a fat-soluble vitamin that the body largely produces itself through sunlight on the skin. It is not a vitamin in the classical sense, but rather a prohormone that plays a crucial role in hormone metabolism, the immune system, bone formation, and muscle strength. It is particularly important for men, contributing to testosterone production , protection against chronic inflammation, and overall performance.
Vitamin D deficiency is widespread in Germany, especially during the winter months, among those who spend a lot of time in an office setting, or with darker skin. Studies show that optimized vitamin D levels correlate with increased muscle mass , higher testosterone levels , improved mood , and fewer infections .
What makes vitamin D so important?
Vitamin D is involved in a variety of bodily processes:
- Regulation of calcium and phosphate metabolism → bone stability, teeth, muscles
- Modulation of the immune system → Protection against infections & chronic inflammation
- Cell division & DNA repair
- Production of sex hormones , especially testosterone
- Muscle strength, coordination & balance
- Mood & Brain Function
An optimal level can therefore help reduce the risk of osteoporosis, autoimmune diseases, infections and hormonal imbalances.
Symptoms of vitamin D deficiency
The symptoms are often nonspecific and develop gradually:
- Chronic fatigue, "winter blues"
- Muscle weakness, reduced regeneration after exercise
- Depressed mood, irritability
- Susceptibility to infection (e.g., frequent respiratory infections)
- Sleep problems
- Bone pain or increased susceptibility to fractures
- Loss of libido, reduced testosterone effect
A long-term deficiency can negatively affect the production of sex hormones, even with otherwise "normal" testosterone levels.
What are optimal values?
Vitamin D is measured in the blood as 25-OH-vitamin D (calcidiol) .
| Value (ng/ml) | Meaning |
|---|---|
| < 20 | Deficiency (requiring treatment) |
| 20–30 | suboptimal |
| 30–50 | good, healthy target range |
| > 60 | Possibly too high (check with a doctor) |
Note: Optimal ranges may vary slightly depending on the laboratory and source. For known risk groups (e.g., chronically ill individuals, seniors, vegans), a value > 40 ng/ml may be appropriate.
Who is particularly at risk?
- People with low sun exposure (office, big city, sunscreen)
- Men with dark skin (less conversion via UV radiation)
- Overweight people (Vitamin D is “stored” in fatty tissue)
- Older men (reduced synthesis in the skin)
- People with chronic bowel diseases or lipid metabolism disorders
- Men with low testosterone or high SHBG
How can the mirror be improved?
1. Soak up the sun
- 15–30 minutes of daylight per day on uncovered skin (face, arms, upper body) - but with sunscreen.
- Effectiveness varies depending on skin type, season, and latitude.
- In Germany, solar radiation is often insufficient between October and March .
2. Nutrition
- Vitamin D is only of limited effectiveness; it is found mainly in fatty fish, egg yolks, liver, and mushrooms.
- Insufficient to meet demand in case of shortage.
3. Supplementation
- Useful in cases of proven deficiency or risk factors.
- Typical dosage: 1000–4000 IU/day - to be adjusted individually.
- Ideal in combination with vitamin K2 and magnesium.
Before supplementing, the level should be checked via a blood test to avoid overdoses.
Connection to testosterone & hormone status
Studies show that men with higher vitamin D levels have, on average , higher testosterone levels, regardless of age and body weight. Vitamin D likely supports the function of the Leydig cells in the testicles, which are responsible for testosterone production.
Sex hormone-binding globulin (SHBG) also appears to be influenced by vitamin D, which in turn determines free testosterone levels . When combined with strength training, this results in an additional synergistic effect: muscle growth, libido, and recovery can all benefit.
Conclusion
Vitamin D is one of the most important micronutrients for men. Its effects extend far beyond the immune system, impacting bones, muscles, libido, mood, and hormonal balance. Anyone who is chronically tired, irritable, or prone to infections, or who suffers from training plateaus, should have their vitamin D levels checked.
A balanced vitamin D level is not a "booster", but a foundation for long-term health and performance, both physical and mental.
If required, vitamin D levels can be determined as part of a comprehensive hormone or micronutrient check, ideal for combination with testosterone, SHBG, magnesium and other health markers.
