(1) Background: One of the ways to prevent nutritional deficiencies may be supplementation. Experts have observed the increased use of dietary supplements, not only in adults but also in children. Considering controversies among dietary supplements and possible errors in children's feeding, the goal of our research was to evaluate use and reasons behind supplementation in terms of children's diet analysis. (2) Methods: Our research involved 507 legal guardians of the youngest children (up to 3 years of age) and was conducted via a questionnaire. (3) Results: 79% of all children received dietary supplements. The analysis of children's diets showed a need to implement omega-3 acids and vitamin D supplementation, which was very low in children. On the other hand, vitamin C, vitamin B, vitamin A, and copper levels were extremely high. (4) Conclusions: Popularity of dietary supplements in Polish children aged 0-3 years old is an omnipresent issue. Although the reasoning behind administering nutritional supplements to children seems justified, considering the supply of vitamin D and omega-3 fatty acids, it seems justified to increase parents' knowledge in this regard in terms of the use and means to choose the best supplement possible, as dietary supplementation should always be tailored to individual needs.
Keywords: contamination; nutritional programming; omega-3 acids; vitamin D.