Schematic outline of the mechanisms of spermidine-mediated health effects. Schematic outline of the mechanisms of spermidine-mediated health effects. The natural polyamine spermidine has prominent cardioprotective and neuroprotective effects, ameliorates aging-associated metabolic decline, and stimulates anticancer immunosurveillance in animal models. Autophagy is required for several of these health-promoting effects of spermidine. Spermidine also suppresses proinflammatory cytokines and improves the bioavailability of arginine required for NO biosynthesis. It remains an open question whether all these effects depend on the autophagy-stimulatory properties of spermidine. Frank Madeo et al. Science 2018;359:eaan2788 Published by AAAS