Kalsiumabsorpsjon

Kalsiumabsorpsjon refers to the physiological process by which calcium ions are taken up from the gastrointestinal tract into the bloodstream. The majority of dietary calcium is absorbed in the duodenum and upper jejunum, with absorption occurring through both active and passive pathways. The active transport mechanism is vitamin D dependent; the active form 1,25-dihydroxyvitamin D stimulates the synthesis of calcium‑binding proteins in enterocytes and increases the transcellular influx of calcium. Passive diffusion, driven by a concentration gradient, contributes significantly when dietary calcium intake is high, and is independent of vitamin D status.

Several factors influence the efficiency of calcium absorption. Adequate vitamin D levels, sufficient dietary calcium, and normal gut integrity are essential. Hormones such as parathyroid hormone (PTH) can enhance calcium uptake during periods of hypocalcemia by upregulating active transport. Conversely, high levels of phytates, oxalates, and excessive sodium or protein intake can inhibit absorption. Age also plays a role; older adults often experience reduced active absorption, which can contribute to bone density loss.

Efficient calcium absorption is critical for skeletal health, muscle function, neuronal signaling, and blood clotting. Deficiencies or impaired absorption can lead to conditions such as osteopenia, osteoporosis, and, in severe cases, hypocalcemic tetany. Public health recommendations typically emphasize adequate dietary calcium, vitamin D sufficiency, and lifestyle measures such as regular weight‑bearing exercise to promote optimal calcium kinetics and maintain bone integrity.