Spermidine

Spermidine is a naturally-occurring polyamine produced by every living cell, with the highest dietary concentrations in wheat germ, soy, and aged cheeses. The reason it's having a moment in skincare: it's one of the only known dietary compounds that reliably triggers autophagy, the cellular recycling process that clears damaged proteins and organelles. Autophagy declines with age, and that decline is increasingly understood as a driver of skin aging — backed-up cellular junk degrades barrier function, slows turnover, and dulls tone. Topical spermidine is dramatically newer than the oral form (where there's a decade of human longevity data), but early formulations from premium K-beauty and J-beauty brands have shown meaningful improvements in barrier integrity and fine lines over 8–12 weeks. Stable, gentle, and pairs well with everything — the catch is cost. Effective formulations typically run premium because pharmaceutical-grade spermidine is expensive to source.