Vitamin D is a fat-soluble vitamin that helps regulate the amount of calcium and phosphate in the body. The recommendation for dietary allowance for Vitamin D for different categories of people are based on scientific research, publications, traditional use, or expert opinion. Recommended daily allowance (RDA) is 600 International Units (IU) for those 1-70 years of age. Here belong also individuals around 20 years of age, so their recommended dietary allowance is also 600 IU.