Researchers in Italy found that by the time most people reached their sixties and seventies, their spermidine levels had already fallen to about a third of what they measured in middle age. But those living into their nineties and beyond were somehow able to maintain their youthful spermidine levels, presumably by just making more of it internally. However, we could also replenish declining levels externally with a spermidine-rich diet. The researchers suggested foods like soybeans and mushrooms,324 but, as we’ll learn, wheat germ is an even more concentrated natural source.
