Vitamin D or otherwise the vitamin of the sun is the only one of the vitamins that is produced in our body, and more specifically, it is produced in our skin with the effect of sunlight in its most active form, cholecalciferol or D3. While we are a Mediterranean country bathed in the sun most months of the year, clinical research proves that we are deficient in vitamin D.
Vitamin D contributes to:
In the normal functioning of the immune system*.
In maintaining the normal condition of bones and teeth *.
In the normal absorption/utilization of calcium and phosphorus*.
In maintaining normal levels of calcium in the blood*.
In maintaining normal muscle function

Vitamin C is one of the most popular dietary supplements. It is the most loved vitamin of all time, because its properties as a food supplement take care of your body regardless of the weather.
Vitamin C contributes to:
In the normal functioning of the immune system*
In maintaining the normal function of the immune system during and after intense physical exercise*
In the normal formation of collagen for the normal function of blood vessels, bones, cartilage, skin and teeth*
In the protection of cells from oxidative stress*
In increasing the absorption of iron*
In the normal functioning of the nervous system*
In normal psychological functioning*
In reducing tiredness and fatigue*

* The above are official health claims from the European Food Safety Authority (EFSA).