The truth about fillers. (Warning: This may shock you) When you look at the label on your supplements you may see a list of ingredients that seem foreign. Manufacturers include these ingredients to meet several key criteria such as stabilization of products, improve flowability, enhance bioavailability, and other functional benefits. These ingredients are called excipients (or “fillers”). We’re going to explore what they are, how they’re used and if they’re even safe.