Zinc balance and the chelating properties of phytic acid

Objectives: Zinc deficiency is recognized as a significant global contributor to morbidity and mortality risk. In the absence of a reliable biological marker for determining the absorption coefficient of dietary zinc, a mathematical model is employed. This systematic review aimed to study this mathematical model and evaluate its potential to calculate the recommended dietary intake of zinc (RDI), compared to actual zinc balance in the human body. Methods: This review analyzes scientific publications from 1980 to 2025 that focus on zinc balance in the bodies of healthy individuals aged 19 and older of both sexes. Special attention is given to experimental results that demonstrate the disruption of the balance between the RDI and the quantity of zinc excreted through the intestines. Results: A systematic review of the literature has shown that the recommended dietary allowances for zinc intake, the absorption rate into the bloodstream, and the intestinal excretion of zinc—all critical factors for assessing zinc balance — exhibit substantial variations according to data from different research groups. The mathematical model used to determine the absorption coefficient and calculate dietary zinc intake norms has limitations, as it does not account for the polydentate nature of phytate ions. Conclusions: The RDI of zinc is lower than the actual requirement and needs adjustments to increase it. The analysis of the zinc balance while considering the polydentate nature of phytic acid can help to make more accurate dietary selections and recommendations for zinc-based supplements, thereby maintaining homeostasis and preventing toxic levels in the body. Keywords: zinc absorption and excretion, zinc homeostasis, phytic acid polydentency