Influential Factors in Intestinal Absorption and Renal Reabsorption of Calcium

Abstract

Calcium is one of the vital and essential elements in the body, serving as a primary constituent of bones and teeth. It plays a fundamental role in nerve signal transmission, muscle contractions, heart rate regulation, blood clotting, energy production, glandular secretion, and immune system maintenance. Calcium is abundantly found in dietary sources, with most of it residing in the teeth and bones within the body. Approximately 40% of daily dietary calcium is absorbed primarily at the beginning of the intestine and before gastric juice neutralization, while 60% of it is excreted through feces. Calcium absorption occurs in two forms, passive and active, through the intestines, and renal reabsorption takes place through the kidneys. Various factors such as intestinal environment, dietary components (including lactose, proteins, and amino acids),bile salts, parathyroid hormone, vitamin D, acidic pH, health status, age, and growth hormone influence intestinal calcium absorption positively. Conversely, fatty acids, phytic acid, aging, alkaline pH, iron, magnesium, calcitonin hormones, and glucocorticoids reduce calcium absorption. Parathyroid hormone, calcitonin hormone, vitamin D, and dietary regimen significantly contribute to the active reabsorption of calcium through renal tubules. Despite the considerable variations in the calcium content of dietary sources, a highly precise regulatory system controls vitamin D production, preventing fluctuations in plasma calcium ion concentrations. This regulation helps prevent hypocalcemia and hypercalcemia, which can lead to numerous irregularities in the body.