An algorithm to assess calcium bioavailability from foods

Background and objectives: Calcium bioavailability from individual foods, beverages, and fortified foods has been determined with calcium isotopic tracers and compared to milk as a referent to adjust for physiological differences of the host. Our objective was to develop a calcium bioavailability algorithm using these data to predict calcium bioavailability in the food supply. Methods: We modeled data from 475 observations to develop a predictive algorithm for calcium bioavailability in adults based on calcium load and oxalate and phytate loads which represent the two main inhibitors of calcium absorption. Results: The calcium bioavailability model was optimized by minimizing the squared residuals between observed data and model-calculated values using the least-squares fitting routine in WinSAAM software. Model development affirmed the effect of calcium load on fractional calcium absorption and the potency of oxalate as an inhibitor of calcium absorption compared to phytate. Conclusions: This algorithm will be helpful in assessing calcium availability from the food supply and for designing policies and interventions to address inadequate calcium intake for populations. It will also be useful for developing diets for individuals, research cohorts, and populations. We plan to work with an international network of scientists to apply this algorithm to countries in South Asia and Africa as test cases.