Nutraceuticals are ingested for health benefits in addition to their general nutritional value. These dietary supplements have become increasingly popular since the late twentieth century and they are a rapidly expanding global industry approaching a half-trillion US dollars annually. Many nutraceuticals are promulgated as potent antioxidants.Experimental support for the efficacy of nutraceuticals has lagged behind anecdotal exuberance. However, accumulating epidemiological evidence, and recent, well-controlled clinical trials, are beginning to support earlier animal and in vitro studies. Although still somewhat limited, encouraging results have been suggested in essentially all organ systems and against a wide range of pathophysiological conditions.Health benefits of the 'antioxidant' nutraceuticals are largely attributed to their ability to scavenge oxidants. This has been criticized based on several factors including limited bioavailability, short tissue retention time, and the preponderance of endogenous antioxidants. Recent attention has turned to nutraceutical activation of downstream antioxidant systems, especially the Keap 1/Nrf2 axis. The question now becomes, how do nutraceuticals activate this axis?Reactive sulfur species (RSS), including hydrogen sulfide (H