CanPrev Iron Bis-Glycinate 25 120 Veggie Caps25mg of pure elemental iron per capsule Chelated iron that is easy to absorb and gentle on the stomach Iron is an oxygen carrier and also a catalyst for enzymatic reactions that help the body with energy production, metabolism and DNA construction. Bumping up iron stores is easy: simply take a daily iron supplement. But not all iron supplements provide a pass from uncomfortable side effects like constipation, diarrhoea, stomach upset and nausea.