Vitamin D3 is an important vitamin for the development of a strong skeleton and teeth. It contributes to the normal absorption of calcium and phosphorus and normal blood calcium levels. Therefore, vitamin D has a significant role in maintaining normal bones and teeth. In summer vitamin D3 is sufficiently formed in the skin when the skin is exposed to sunlight. Dietary sources of vitamin D3 are limited as it is only present in fish and egg yolk as well as fortified milk and dairy products and margarine. If consumption of fish is less than 2-3 times a week, consumption of milk is low or someone follows a vegetarian diet, the recommended amount of vitamin D from the diet is impossible to reach, and development of vitamin deficiency is obvious at every age. A food supplement is not a substitution for a varied and balanced diet and healthy lifestyle.