Vitamin D: the deficiency that affects 40% of Europeans

Vitamin D deficiency is so common in Central and Northern Europe that calling it an epidemic is barely an exaggeration. Studies consistently show that 40–60% of adults in the DACH region (Germany, Austria, Switzerland) have insufficient vitamin D levels, with rates climbing above 80% in winter months.

Despite this, vitamin D is one of the most misunderstood nutrients. The wellness industry has inflated its importance beyond what the evidence supports, while conventional medicine has often been too dismissive. Here's what we actually know.

What vitamin D does — and doesn't do

The evidence for vitamin D is genuinely strong in two areas: bone health and immune function. Severe deficiency causes rickets in children and osteomalacia in adults. Moderate deficiency increases fracture risk, particularly in older adults. Supplementation in deficient individuals reduces fracture rates — this is well-established in multiple randomized trials.

For immune function, the evidence is strong but less dramatic. Vitamin D plays a documented role in innate immune regulation. Deficiency is associated with increased susceptibility to respiratory infections. A large meta-analysis of individual patient data found that supplementation reduced acute respiratory infections by about 12% overall, and by 70% in people with severe deficiency.

Where the evidence gets weaker is the long list of other conditions vitamin D has been linked to: cardiovascular disease, cancer prevention, depression, autoimmune diseases, cognitive decline. For most of these, the associations are real but the causation is unproven. Large randomized trials (particularly VITAL, n=25,871) did not show that vitamin D supplementation prevents cancer or cardiovascular disease in people who aren't deficient.

What levels actually matter

Vitamin D levels are measured as 25-hydroxyvitamin D (25-OH-D) in ng/mL:

• Below 20 ng/mL: Deficient. Supplement with 4,000 IU daily. Recheck in 3 months.
• 20–30 ng/mL: Insufficient. Supplement with 2,000 IU daily.
• 30–60 ng/mL: Sufficient. No supplementation needed unless symptomatic.
• Above 100 ng/mL: Potentially toxic. Stop supplementation immediately.

Our target range at Health Detectors is 40–60 ng/mL, which reflects the range where bone and immune benefits are well-established without toxicity risk.

Why US patients in Munich should care

Munich sits at 48°N latitude — roughly the same as Vancouver or Paris. From October to March, the sun angle is too low for meaningful vitamin D synthesis through the skin. If you're visiting Munich in winter for your Health Detectors assessment, there's a very good chance your vitamin D is on the low side, regardless of how much time you spend outdoors at home.

We include 25-OH vitamin D in our core DETECT panel. If it's low, the treatment is simple and cheap — oral supplementation. No infusion, no injection, no exotic formulation. Just a pill.