Vitamin D is central to health, but many people are not adequately supplied with it. Broken bones and an increased risk of respiratory disease can be the result of a deficiency. Vitamin D is available in two variants: as vitamin D2 and D3. Vitamin D3 is formed in the human skin by the action of sun rays. So, humans cover about 90 % of their needs. The rest is ideally absorbed through the diet.
Vitamin D2 occurs, for example, in mushrooms.

A research group from Martin Luther University Halle-Wittenberg (MLU) and the Max Rubner Institute (MRI) has identified a previously unknown source of vitamin D2: Cocoa and cocoa-containing foods contain significant amounts of the important nutrient. According to the researchers, cocoa butter and dark chocolate have the highest vitamin D2 content. In a study by the nutritionist Prof. Gabriele Stangl of the MLU, the researchers examined the vitamin D content of cocoa and cocoa-containing products because they suspected a previously unknown source of the vitamin.

Cocoa beans are dried after fermentation. They are placed on mats and exposed to the sun for one to two weeks. Due to the sunlight, the precursors of vitamin D, which probably originate from harmless fungi, convert to vitamin D2.

To test their idea, the research group analysed various cocoa products and cocoa powders using modern methods. The result: cocoa-containing products are a source of vitamin D2, but the content varies greatly. While dark chocolate has a relatively high vitamin D2 content, researchers found little of it in white chocolate. This is not surprising, because the cocoa content in white chocolate is much lower. This confirms the assumption that cocoa is the source of vitamin D2.