Adequate vitamin D intake and its status as well outdoor physical activity are important not only for normal bone development and Ca-P metabolism, but for optimal function of many organs and tissues throughout the body. Due to documented changes in dietary habits and physical activity level, both observed in growing children and adults, the prevalence of vitamin D insufficiency is continuously increasing. National Consultants and experts in this field established the Polish recommendations for prophylactic vitamin D supplementation in infants, toddlers, children and adolescents as well as in adults, including pregnant and lactating women based on current literature review. Taking into consideration pleyotropic vitamin D action and safety aspects serum 25-hydroxyvitamin D (25-OHD) level of 20-60 ng/ml (50-750 nmol/l) in children and 30-80 ng/ml (75-200 nmol/I) in adults is considered as optimal. Sunlight exposure inducing vitamin D production in the skin is main endogen source of vitamin D in the body but sunscreens may reduce skin synthesis by 90%. In Poland, skin synthesis is effective only from April to September so other sources of vitamin D such as diet and supplements play an important role. All newborns should be supplemented with 400 IU/d of vitamin D beginning from the first few days of life and continue during infancy. In formula fed infants vitamin D intake from the diet should be taken into account. In preterm infants higher total vitamin D intake (400-800 IU/day) is recommended till 40 weeks post conception. Total vitamin D intake in children and adolescents required from all sources (diet and/or supplements) should be 400 IU/d between October and March and throughout the whole year in case of inadequate vitamin D skin synthesis during the summer months. In overweight/obese children supplementation with higher dosage of vitamin D up to 800-1000 IU/d should be considered. Adults require 800-1000 IU/d of vitamin D. In pregnant and lactating women such supplementation is recommended in case of inadequate intake from diet and/or skin synthesis supplementation. Monitoring of serum 25-OHD level to define optimal dosage should be considered.