The 15mg/d they used in that study is just the standard dietary intake (top end, europeans). Looked a number of other studies that also used just regular intake levels as "supplementation". Weird how they all stay small when the no observable adverse effects level is much higher.

>(3) Results: Compared with a placebo, spermidine supplementation significantly increased spermine levels in the plasma, but it did not affect spermidine or putrescine levels. No effect on salivary polyamine concentrations was observed.

Which might be fine if the metabolite is actually the responsible molecule.

Helpful reminder that mice lie, monkeys exaggerate, and ferrets are not people (surprisingly enough).

Order? Considering the source of Spermidine, might be easier to get it for free from your local glory hole