For centuries, Curcuma longa (turmeric) was used as a spice in Asian cuisine and as a medicinal herb for treatment of inflammation, pain, wound healing, and digestive disorders, to name a few. Considerable preclinical research found that turmeric and its bioactive curcuminoid polyphenols can affect a variety of chronic conditions. Poor oral bioavailability of these curcuminoids hindered human trials investigating the efficacy of oral turmeric and its curcuminoids in treating various diseases and disorders. However, with the development of absorption-enhanced curcuminoid formulations in the past decade, dozens of clinical studies were conducted examining this spice's actions toward inflammatory conditions and glucose/lipid dysregulation. This narrative review of human trials addresses the scientific evidence for potential health benefits of turmeric and its curcuminoids in the treatment of arthritis, diabetes, and the metabolic syndrome and discusses recommendations for future research.