Are we overrating the extra-skeletal benefits of oral vitamin D supplementation?

摘要

Vitamin D (Vit D) is a fat-soluble hormone poorly present in food, which is endogenously produced mainly through the biological conversion of its precursors into the biologically active form (1,25-dihydroxy-cholecalciferol) triggered by ultraviolet radiation exposure from either sunlight or, less frequently, indoor tanning ( ). According to the Endocrine Society recommendations, Vit D3 deficiency can be diagnosed when serum 25-hydroxyvitamin D (25OHD) concentration falls below 20 ng/mL (i.e., ≤50 nmol/L), whilst Vit D3 insufficiency is conventionally defined as a serum 25OHD concentration between 21–29 ng/mL (i.e., 52.5–75.0 nmol/L) ( ). Although severe forms of Vit D3 deficiency are relative rare and mainly manifest as rickets ( ), the current worldwide burden of Vit D3 deficiency and insufficiency is alarming, being recently estimated at around 20% and 50%, respectively ( ). This evidence has paved the way to widespread serum Vit D3 testing ( ), enhanced oral Vit D3 supplementation ( ) and even food fortification in several countries around the world, such as Canada, United States, Finland and India ( ). For example, the Endocrine Society currently recommends that at least 600 IU/day of oral Vit D3 are needed in the adulthood to optimize bone health and muscle function ( ).