Vitamin D3 Interactions

Vitamin D3 increases calcium absorption and stimulates production of vitamin K-dependent proteins (osteocalcin, matrix Gla protein) that themselves require K2 for activation. Co-supplementation supports bone density and may reduce vascular calcification compared with D3 alone.

Vitamin D (via VDR) and vitamin A (via RXR, the obligate heterodimer partner of VDR) bind together at vitamin D response elements to drive gene transcription for immunity, bone, and epithelial differentiation. Adequate levels of both are needed for optimal signaling, but at very high doses they can antagonize each other for bone and calcium endpoints.