Vitamin D is no ordinary vitamin – it is a hormone that influences virtually every cell in the human body. Prof. Dr. Jörg Spitz, one of the leading Vitamin D experts in the German-speaking world, has devoted decades to studying this fascinating messenger substance.
The skin functions as a highly efficient solar power plant: under the influence of UVB radiation, it converts the precursor molecule 7-dehydrocholesterol into previtamin D3, which is then activated in the liver and kidneys to the biologically active form calcitriol. This process is evolutionarily optimised – and chronically disrupted in our modern world of indoor living and sun protection.
Vitamin D deficiency is widespread: estimates suggest that over 60 percent of the population in Germany have suboptimal levels. Particularly affected are older people, those with darker skin types, people who spend little time outdoors, and obese individuals – since Vitamin D is fat-soluble and stored in adipose tissue.
The function of Vitamin D extends far beyond bone metabolism. It regulates the immune system, inhibits excessive inflammatory responses, protects nerve cells, controls the cell cycle, and has demonstrably cancer-inhibiting effects. Prof. Dr. Spitz explains compellingly why cancer cells don't like sunshine: calcitriol promotes cell differentiation and inhibits uncontrolled cell growth.
In his books, lectures, and congresses, Prof. Dr. Spitz provides practical recommendations for optimal Vitamin D supply. He advocates regular measurement of 25-OH-Vitamin-D levels in the blood and individual supplementation when endogenous production is insufficient. Target values of 40–60 ng/ml are considered optimal according to current research.