HUMAN NUTRITION

Detailed explanation-1: -The body needs vitamin D to absorb calcium. Without enough vitamin D, one can’t form enough of the hormone calcitriol (known as the “active vitamin D”). This in turn leads to insufficient calcium absorption from the diet.

Detailed explanation-2: -The principal function of vitamin D in calcium homeostasis is to increase calcium absorption from the intestine. Calcium is absorbed by both an active transcellular pathway, which is energy dependent, and by a passive paracellular pathway through tight junctions.

Detailed explanation-3: -Calcium is actively absorbed from the small intestine in the presence of vitamin D. Calcium and phosphorus form hydroxyapatite crystals to mineralize and strengthen bones. Thus, a diet containing both optimal vitamin D and calcium is important for proper mineralization of bone.