Nutritional Supplement. Immune & Bone Health. Health Booster. Great Tasting. Rapid Absorption. Natural Fruit Flavoring. 1200 IU-Adults. 400 IU-Children. 1st Step supplements are purchased by over 200 professional and university sports teams because they work. Better Vitamin Absorption. Vitamin D is an essential nutrient that helps infants, children, adolescents and adults with Vitamin D deficiency. Recent studies have shown Vitamin D intake can also aid in maintaining breast and colon health. Vitamin D3 is an essential nutrient in the development of strong bones and help to promote a healthy immune system. The American Academy of Pediatrics now recommends that infants, children and teens should take 400 IU per day in supplement form.