Vitamin D3 (cholecalciferol) What: Natural vitamin D made in skin from sun; also an oral supplement. Roles: Aids calcium absorption for bone health, supports immunity, muscle function, and mood. Sources: Sun (UVB), fatty fish, fish liver oils, fortified foods, supplements. Doses: OTC 1,000–2,000 IU/day; deficiency treatments 5,000–50,000 IU/week under medical supervision. Deficiency: Fatigue, bone pain, muscle weakness, higher infection risk; severe cases: osteomalacia/rickets.
Vitamin D3 (cholecalciferol) What: Natural vitamin D made in skin from sun; also an oral supplement. Roles: Aids calcium absorption for bone health, supports immunity, muscle function, and mood. Sources: Sun (UVB), fatty fish, fish liver oils, fortified foods, supplements. Doses: OTC 1,000–2,000 IU/day; deficiency treatments 5,000–50,000 IU/week under medical supervision. Deficiency: Fatigue, bone pain, muscle weakness, higher infection risk; severe cases: osteomalacia/rickets.