What is the Origin of Vitamin D Bioavailability?

The term combines the nutritional concept of "bioavailability" with the endocrinological understanding of Vitamin D as a secosteroid hormone. Its origin is in nutritional science and clinical endocrinology, where the active form, calcitriol, is known to regulate gene expression. This concept refines the clinical approach to Vitamin D status.

What is the Mechanism of Vitamin D Bioavailability?

Vitamin D, whether from diet or sun exposure, must be hydroxylated in the liver and then the kidney to its active form, 1,25-dihydroxyvitamin D. Bioavailability is affected by gut health, liver and kidney function, and the concentration of its binding protein. Once active, it binds to the Vitamin D Receptor (VDR) to modulate the expression of hundreds of genes, impacting calcium homeostasis, immune function, and endocrine signaling.

Vitamin D Bioavailability ∞ Area

Vitamin D Bioavailability

Meaning

Vitamin D Bioavailability is the fraction of ingested or synthesized Vitamin D that is effectively absorbed, metabolized, and available to exert its biological effects on target tissues. This is a crucial metric that goes beyond simple serum concentration to account for factors like intestinal absorption, liver and kidney conversion efficiency, and transport protein binding. Optimal bioavailability is essential for its function as a potent secosteroid hormone.