Phytic acid-trace element (Zn, Cu, Mn) interactions

Studies in animals and human subjects have shown that diets high in phytic acid can cause zinc deficiency, and that the phytate content is negatively correlated to zinc absorption. Suboptimal zinc status has been shown to cause increased morbidity, poor pregnancy outcome, impaired growth, immune competence and cognitive function, emphasizing the need to optimize zinc bioavailability. Reducing the content of phytate in the diet is one way of improving zinc absorption and this can be achieved by novel precipitation methods during processing, food preparation methods that activate endogenous phytase (e.g. baking, fermentation, malting and hydrothermal processing), or addition of exogenous phytase. During the action of phytase on phytic acid, the hexaphosphate is hydrolysed into inositol phosphates with lower degrees of phosphorylation. Because only the penta- and hexaphosphates have been shown to inhibit zinc absorption, it is often essential to analyze the individual forms of phytate in the diet when evaluating zinc bioavailability. Phytic acid does not inhibit copper absorption, but has a modest inhibitory effect on manganese absorption.