The effect of phytic acid on in vitro rate of starch digestibility and blood glucose response

Abstract

The effect of phytic acid on starch digestibility was studied in vitro and related to the blood glucose response (glycemic index) in healthy volunteers. The glycemic index was found to correlate negatively with the phytic acid content of the food tested. In vitro digestion studies involving human saliva at physiological pH and temperature showed that in the presence of sodium phytate (equivalent to 2% phytic acid based on the starch portion), the rate of digestion of raw wheat starch was reduced significantly by 50%. This was reversed by the addition of calcium which is known to complex phytic acid. Similarly, when sodium phytate was added to unleavened bread, its digestibility was also decreased and in feeding trials high phytate bread produced a flattened blood glucose response.