Spermidine is also pretty high in fermented cheeses and mushrooms.

Spermidine causes damaged cells to be cleared through a process known as autophagy which has itself been shown to extend healthspan of animals.

In this study, mice had to be fed spermidine from weaning in order to get the 25% lifespan extension. Those mice that were fed spermidine starting in early adulthood only had a 10% increase in lifespan.