Which nutrient is often paired with calcium to aid absorption for bone health?

• A. Vitamin C
• B. Vitamin D
• C. Vitamin A
• D. Vitamin E

Answer: (B)

Calcium works best for bone health when the body can absorb it efficiently, and vitamin D is the nutrient that makes that possible. The active form of vitamin D, calcitriol, signals intestinal cells to produce calcium-binding proteins and transport mechanisms, so more calcium moves from the gut into the bloodstream for incorporation into bone. Adequate vitamin D can come from sun exposure, foods like fatty fish and fortified products, or supplements. Without enough vitamin D, calcium absorption is limited, even with adequate calcium intake, which is why these two are commonly paired on bone-support supplements. The other vitamins listed—C, A, and E—have important roles in health but do not primarily boost calcium absorption in the gut.