[Update on recent progress in vitamin D research. Eldecalcitol and intestinal calcium absorption.]

Though various physiological actions have been attributed to vitamin D, its most important function is to promote absorption of calcium from the intestinal tract. While the absorption rate of calcium is generally low, it tends to decline further with age. In addition, calcium intake is decreasing in recent years in Japan. Therefore, it is important to increase the intestinal calcium absorption rate. Eldecalcitol has been shown to increase calcium absorption from the intestinal tract, suppress bone resorption, increase bone mineral density, and prevent fractures. Elocalcitol use leads to a lower systemic active vitamin D[1α,25(OH)2D]concentration, compared to that with alfacalcidol use. This is because eldecalcitol inhibits vitamin D activation in the kidney. Therefore, it is presumed that the calcium absorption-boosting effect of eldecalcitol is not due to the action of 1α, 25(OH)2D, but due to eldecalcitol itself.