However, iron supplementation is not a simple matter. Such supplements can cause constipation and stomach irritation by ionizing the stomach lining. Consequently, this cuts down on the absorption of other vitamins and minerals.
Insoluble iron sources, like ferrous sulfate, are more bioavailable and less inclined to produce these adverse affects. Unfortunately, insoluble iron reacts with ingredients in food products, causing instability initiated by pH, heat and oxidation. Acting as a pro-oxidant, iron presents a significant formulation challenge that is discernible by precipitation and an unappealing “iron” flavor and color.