Background: Spermidine administration is linked to increased survival in several animal models.
Objective: The aim of this study was to test the potential association between spermidine content in diet and mortality in humans.
Design: This prospective community-based cohort study included 829 participants aged 45-84 y, 49.9% of whom were male. Diet was assessed by repeated dietitian-administered validated food-frequency questionnaires (2540 assessments) in 1995, 2000, 2005, and 2010. During follow-up between 1995 and 2015, 341 deaths occurred.
Results: All-cause mortality (deaths per 1000 person-years) decreased across thirds of increasing spermidine intake from 40.5 (95% CI: 36.1, 44.7) to 23.7 (95% CI: 20.0, 27.0) and 15.1 (95% CI: 12.6, 17.8), corresponding to an age-, sex- and caloric intake-adjusted 20-y cumulative mortality incidence of 0.48 (95% CI: 0.45, 0.51), 0.41 (95% CI: 0.38, 0.45), and 0.38 (95% CI: 0.34, 0.41), respectively. The age-, sex- and caloric ratio-adjusted HR for all-cause death per 1-SD higher spermidine intake was 0.74 (95% CI: 0.66, 0.83; P < 0.001). Further adjustment for lifestyle factors, established predictors of mortality, and other dietary features yielded an HR of 0.76 (95% CI: 0.67, 0.86; P < 0.001). The association was consistent in subgroups, robust against unmeasured confounding, and independently validated in the Salzburg Atherosclerosis Prevention Program in Subjects at High Individual Risk (SAPHIR) Study (age-, sex-, and caloric ratio-adjusted HR per 1-SD higher spermidine intake: 0.71; 95% CI: 0.53, 0.95; P = 0.019). The difference in mortality risk between the top and bottom third of spermidine intakes was similar to that associated with a 5.7-y (95% CI: 3.6, 8.1 y) younger age.
Conclusion: Our findings lend epidemiologic support to the concept that nutrition rich in spermidine is linked to increased survival in humans. This trial was registered at www.clinicaltrials.gov as NCT03378843.