A. The measurement of enzyme potency in supplements is more complex than measuring the potency of vitamins, minerals, or herbs. Unlike herbs and vitamins, the relevant units for enzymes are activity units, rather than weight units. Accurate measurement of enzyme activity depends on enzyme concentration, environment (pH and temperature), and the substrate upon which the enzymes act. Several different units are used to measure enzyme activity. The most common enzyme unit systems are Food Chemicals Codex (FCC), United States Pharmacopeia (USP), and Federal Internationale Pharmaceutique (FIP). Each unit system has its own assay methods and specified environmental conditions (like pH). The digestive tract has varying pH levels: the stomach’s pH is very acidic, while the pH of the intestines is more alkaline. The pH can also vary depending upon an individual's health status. For example, one unit used to quantify activity of the enzyme protease is Hemoglobin Unit Tyrosine (HUT). Others include USP and PC units. At Integrative Therapeutics, we use all three because we must be certain that the enzymes are active across the full physiologic range of pH. The USP and PC units measure protease activity in the alkaline pH range (pH 7.5 and pH 7.0, respectively), whereas HUT measures protease activity in a more acidic environment (pH 4.7). Multiple testing methods are the only way to demonstrate this range of activity.