Vitamin D and mood - the sunshine vitamin for your soul

The "Sunshine Vitamin" and Your Soul

It’s the same story every year: Starting in October, as the hours of sunlight dwindle, so does your mood. You feel more tired, less motivated, maybe even sad—for no apparent reason. What if it’s not your attitude, but a vitamin?

Strictly speaking, vitamin D is a hormone—and it plays a central role in your mental health. According to the Robert Koch Institute, about 60% of the population in Germany has insufficient vitamin D levels. In the winter months, the number is even higher.

What does vitamin D do in your body?

Vitamin D is involved in over 1,000 genetic processes. Particularly relevant for your mental health:

• Serotonin synthesis — Vitamin D activates the genes that convert tryptophan into serotonin
• Neuroprotection — protects nerve cells from oxidative stress and inflammation
• Immune regulation — a balanced immune system is essential for mental well-being
• Sleep quality — influences melatonin production and thus your sleep-wake cycle

Recognizing Vitamin D Deficiency

The symptoms are often nonspecific—and are therefore overlooked:

• Persistent fatigue and exhaustion
• Depressive mood, especially in winter
• Muscle pain and weakness
• Susceptibility to infections
• Hair loss
• Difficulty concentrating

At-risk groups

Those at particular risk include: people in Northern Europe (above the 50th parallel, UV radiation is insufficient from October through March), office workers, older adults, people with dark skin, and anyone who spends little time outdoors.

Did you know? According to the Robert Koch Institute, around 60% of the population in Germany have insufficient vitamin D levels - especially in the winter months from October to March, when there is not enough UVB radiation.

How to Boost Your Vitamin D Levels

1. Sunlight (the best source)

15–20 minutes of sun daily on your face and forearms—without sunscreen—from April through September. In winter, UVB radiation in Germany is too weak for vitamin D synthesis.

2. Food

Natural sources: fatty fish (salmon, herring, mackerel), egg yolks, mushrooms (especially if they’ve been exposed to UV light), liver. However, food covers a maximum of 10–20% of your needs.

3. Supplementation

During the winter months, many doctors recommend a daily supplement of 1,000–2,000 IU. Optimal: Have your blood 25-OH-D level checked beforehand (target range: 40–60 ng/ml).

4. Combination with Vitamin K2

Vitamin D improves calcium absorption. Vitamin K2 ensures that calcium is incorporated into the bones and does not end up in the blood vessels. The combination is recommended.

Can vitamin D cure depression?

Vitamin D alone does not cure depression. However, studies show that optimizing vitamin D levels in people with a deficiency can improve depressive symptoms. It is an important building block - alongside therapy, exercise and social connection.

Is it possible to overdose on vitamin D?

An overdose via sunlight is not possible. With supplements, hypercalcemia can occur if you take more than 4,000 IU per day without medical supervision. Have your levels checked regularly.

How do I know if my vitamin D level is too low?

The only reliable method is a blood test (25-OH vitamin D). The symptoms (tiredness, low mood, infections) are too unspecific for self-diagnosis. The test costs around 20-30 euros as an IGeL service.

Is a walk in winter enough for vitamin D?

Unfortunately not. In Germany (from 50 degrees latitude), the sun is too low from October to March to provide sufficient UVB rays. Walking in winter is nevertheless valuable - for exercise, fresh air and stress relief.