Most authors define vitamin D in normal range from 30 to 100 ng/mL, which might be the optimal range to ensure its immunoregulatory effects; insufficient between 20 and 29 ng/mL, and deficient if serum levels are <20 ng/mL (50 nmol/L), since this level is necessary to maintain optimal bone mineralization and calcium homeostasis in 97.5% of the population [109,110].