The 3000 GDU in Doctor's Best® High Potency Bromelain refers to the standardization of enzymatic potency and reflects the quality of the raw material used in the product. Bromelain is an enzyme derived from pineapple stem and fruit that has proteolytic (protein-digesting) properties. The bromelain found in High Potency Bromelain 3000 GDU is the most potent form of this enzyme available!