Aim. To determine the reasons of vitamin D deficiencies detected in the Spanish infant-juvenile population.Method. Different databases of scientific publication were consulted through a systematic review. , Systematic reviews and original articles of meta-analyses were used to fulfill the proposed objective.Results. The evidence reveals that there are many causes that result in a decrease in vitamin D levels in the population under study: pregnancy and lactation, food, diseases, medications and sun exposure; being the latter the most influential as the main source of this vitamin and having numerous barriers that prevent solar radiation from making its effect on existing precursors in the dermis.Conclusions. No general recommendations can be made to prevent vitamin D deficiency in the Spanish child and adolescent population with the results obtained. More studies are needed to specify adequate levels and to determine if there is a real deficiency of this micronutrient in our community.