Bioavailability: What the “Nutrition Facts” panel doesn’t reveal
Research Dietitian, Osteoporosis Research Center, Creighton University Medical Center
It is well established that the amount of calcium varies from one food to the next. The same applies to calcium absorption. Rafferty’s team has shown that the absorption of tricalcium phosphate, the form of calcium most often used to fortify soy beverages, is only 75% of that of milk calcium. They evaluated the physical characteristics of fortified soy and rice beverages. Contrary to the calcium found in milk, which is evenly dispersed, one-third to two-thirds of the calcium in the fortified soy and rice beverages didn’t remain suspended; rather, it tended to settle and form a residue at the bottom of the container. Consequently, due to the variable bioavailability of the added calcium, fortified soy and rice beverages do not consistently provide the amount of calcium indicated on the label.
