4.1. Brief Synopsis of Key Findings
To the best of our knowledge, this is the first randomized placebo-controlled pharmacokinetic study with spermidine in humans. Previous data on the pharmacokinetics of spermidine are either based on animal studies only or on clinical trials that do not meet the standards of pharmacokinetic studies. Most strikingly, we found that oral intake of spermidine at 15 mg/d for 5 days increased spermine levels in the plasma but not levels of spermidine or putrescine. Similarly, a nonsignificant trend indicated that spermidine supplementation increased fasted matutinal spermine plasma concentrations but not respective spermidine and putrescine concentrations.