With proper attention to dietary manipulation, adequate calcium balance should be attained. A number of carbohydrates and glucose polymers enhance the intestinal absorption of calcium. The precise mechanism through which these carbohydrates modify intestinal calcium absorption is unclear, but it is known that absorption occurs via a process that is independent of the actions of vitamin D. Osmotic forces that enhance the net intestinal absorption of water also enhances the passive absorption of calcium. Fractional intestinal absorption of calcium is enhanced by dietary restriction of calcium or inorganic phosphate. Under these conditions there is increased production of 1,25-dihydroxyvitamin D with resultant increase in active intestinal absorption of calcium.
Fat malabsorption has the potential to impair intestinal calcium absorption.
Preterm infants are not likely to have an intraluminal concentration of bile salts which is sufficient for the establishment of a micelle-phase, leading to reduced absorption of fat. The unabsorbed free fatty acids are then available to interact with ionic calcium to form insoluble soaps which are not available for absorption. Significant amounts of endogenous calcium are lost daily through intestinal secretion. This portion of the intraluminal calcium is reabsorbed at a level of efficiency less than that of dietary calcium. Compared to calcium, much less is known about the intestinal absorption of inorganic phosphate.