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How can poor absorption of calcium and vitamin D affect bones?

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bone disease Defect of tibia, caused by septic osteomyelitis in childhood, with compensatory thickening of the fibula (right). Normal bones are shown at left.

Poor absorption of calcium and vitamin D significantly compromises bone health by preventing proper mineralization, which is essential for maintaining bone strength and rigidity.123

When the body cannot absorb sufficient calcium—a process heavily dependent on the active form of vitamin D, calcitriol—serum calcium levels drop. In response, the parathyroid glands secrete parathormone, which triggers the mobilization of calcium from the bones into the bloodstream to maintain vital functions like muscle contraction and nerve transmission.423

While the body continues to produce the protein matrix (osteoid) of the bone, the lack of available minerals means this matrix remains poorly calcified. This leads to the softening of bones, resulting in:3

Rickets: A condition in children characterized by stunted growth, bone deformities (such as bowlegs or knock-knees), and enlarged joints.3
Osteomalacia: A condition in adults involving bone pain, muscle weakness, and an increased susceptibility to fractures.53

Ultimately, these deficiencies disrupt the balance between bone formation and resorption, leading to structurally weak and brittle skeletal tissue.12