Objective: Insoluble dietary fiber is a known inhibitor of mineral absorption, whereas the effects of soluble dietary fibers (including prebiotics) are less known. The aim was to study calcium, iron, and zinc availabilities from dairy infant formulas supplemented with soluble dietary fibers and modified starches in vitro.
Methods: Dairy infant formulas were supplemented with soluble dietary fibers (3%, dry wt) and modified starches (16% pregelatinized rice starch and 1.9% maltodextrin, dry wt) and kept in a well-controlled and defined environment in vitro. Pooled mature human milk was used as the reference standard.
Results: Calcium availability from standard formula was elevated by 30% after inulin supplementation (17.2%), whereas locust bean gum (11.9%) and high esterified pectin (11.7%) reduced availability by approximately 10%. Iron availability from standard formula was increased by pregelatinized rice starch (3.8%), whereas availability was reduced in the following order: high esterified pectin (2.3%), oligofructose (2.2%), and low esterified pectin (2.1%). Zinc availability was highest after the addition of pregelatinized rice starch (13.5%) but lowest with the addition of locust bean gum (6.8%) and maltodextrin (5.4%).
Conclusions: This study showed that addition of soluble dietary fiber affects calcium, iron, and zinc availabilities in positive (inulin) and negative ways, depending on the type of the dietary fiber used.