Calcium absorption dynamics in the presence of ferrous salts

Abstract

This study investigates the complex dynamics of calcium absorption from various sources in the presence of ferrous salts, with a focus on the roles of lactate and gluconate anions. Using a Caco-2 cell model, we examined the absorption of calcium chloride, calcium lactate, and calcium gluconate, and the effects of corresponding ferrous salts on their absorption. Calcium lactate demonstrated the highest absorption rate (6.03 % ± 0.7 %), followed by calcium gluconate (5.40 % ± 0.58 %) and calcium chloride (4.97 % ± 0.23 %). The presence of ferrous salts generally inhibited calcium absorption, with varied degree of inhibition according to different combinations of calcium and iron salts. Analysis of calcium transport pathways revealed that ferrous salts did not significantly affect TRPV6 and claudin-2 expression but decreased calbindin-D9k expression, potentially reducing intracellular calcium retention. The study also found that ferrous salts downregulated DMT1 expression, suggesting a compensatory response to excessive iron uptake. Kinetic studies of intracellular calcium uptake showed that calcium chloride had the fastest uptake rate, followed by calcium lactate and calcium gluconate. The addition of ferrous salts generally slowed calcium uptake, but lactate and gluconate anions mitigated this inhibitory effect, may due to the weaker oxidative stress levels. These findings provide new insights into the mechanisms of calcium absorption in the presence of iron and highlight the potential of hydroxycarboxylates in optimizing mineral supplementation strategies. The results have important implications for the development of more effective and compatible mineral supplements, particularly in addressing concurrent calcium and iron deficiencies.