MK-7 form of Vitamin K2 — the longest-acting K2 form with a ~72-hour half-life (vs. ~4 hours for MK-4), ensuring continuous calcium-directing protein activation. Activates two critical calcium-binding proteins: Osteocalcin (binds calcium into bone matrix, supporting density and structural integrity) and Matrix Gla Protein/MGP (inhibits calcium deposition in vascular smooth muscle, protecting arterial flexibility). Without K2, increased calcium availability from D3 supplementation may be misdirected to soft tissue instead of bone. K2 does not increase calcium absorption — it directs where existing calcium goes. The most effective K2 form for vascular outcomes.