Vitamin D is naturally synthesized in the skin when it is exposed to sunlight. However, there are moments, especially in winter time, when it becomes an essential to supplement it by selection of appropriate supplementation. What benefits can you expect? First of all, the proper regulation of calcium - phosphorus balance - and thus strengthening of bones and skeletal elements. Vitamin D also supports and strengthens the immune system, especially during long and intense exercises. It also has an influence on the functioning of the nervous and muscle systems, and it also is a factor reducing inflammation.