Spermidine is found in foods with strong smells like natto, durian fruit, and unpasteurized fermented cheese, as well as in some vegetables and foods where its scent is masked by other molecules.

“So it is frequently found in food items that have some kind of smell like natto or durian fruit or fermented cheese, when it is generated from non pasteurized sources and very rich in bacteria and fungi that are contributing to the fermentation process, which is, of course, smelly cheese. And it's also quite abundant in some vegetables and food where the scent is more agreeable to most people because it is complex to other molecules that reduce its volatility.”