This comprehensive guide explores six of the most popular science-backed anti-aging ingredients—NMN, AKG, PQQ, Urolithin A, Ergothioneine, and Spermidine. Each compound is analyzed for its unique mechanisms, clinical evidence, and ideal use cases. With detailed comparisons and practical suggestions, readers can identify which ingredient or combination best suits their needs, whether the goal is boosting energy, protecting brain health, or enhancing longevity.