Supplement
Spermidine
Spermidine induces autophagy in laboratory models and extends lifespan in several model organisms, which made it one of the most hyped supplement candidates. The human evidence tells a humbler story: dietary intake associates with lower mortality in cohorts, but the flagship randomised trial of supplementation found no cognitive benefit.
Quick verdict
Higher dietary spermidine intake is associated with lower mortality in observational data. The main randomised supplementation trial in older adults found no significant effect on memory. Association plus a null trial equals an open question, not a longevity supplement.
The assessment
Claim by claim
Each claim is graded on its own evidence. A grade for one claim says nothing about the others.
| Claim | What was measured | Evidence |
|---|---|---|
| Higher dietary intake is associated with lower mortality | Lifespan | Early |
| Improves memory in older adults | Physical function | Against |
Higher dietary intake is associated with lower mortality
Early human evidenceOutcome measured: Lifespan — Death from any cause was measured.
A 20-year prospective study of 829 adults found higher dietary spermidine intake associated with lower all-cause mortality.
Why this grade — the appraisal in full
One or a small number of small, short or preliminary human studies. Directionally interesting, not yet dependable.
- Strongest study design. Prospective cohort with 829 participants.
- Human research volume. 1 human study, 829 participants in total.
- What was measured. 1 human study measured a clinical or functional outcome rather than a laboratory marker alone.
- Replication. The supporting result has not been independently replicated in humans.
- Study duration. Longest human study ran 1040 weeks.
Limitations. People who eat spermidine-rich diets (whole grains, vegetables, fermented foods) differ from those who do not in many ways adjustment cannot fully capture. Dietary association says nothing about supplements.
| Study | Design | Population | Finding |
|---|---|---|---|
| [1]Higher spermidine intake is linked to lower mortality: a prospective population-…The American journal of clinical nutrition · 2018 · PMID 29955838 | Prospective cohortHuman | 829 participantsMixed population | Supports the claim20-year population-based prospective study; higher dietary spermidine intake linked to lower mortality. |
Improves memory in older adults
Evidence against the claimOutcome measured: Physical function — A measured capability such as walking speed, grip strength or VO₂ max.
The SmartAge randomised trial gave spermidine supplements to older adults with subjective cognitive decline for 12 months and found no significant improvement in memory versus placebo.
Why this grade — the appraisal in full
Well-conducted human research indicates the claimed effect does not occur, or is too small to matter.
- Strongest study design. Randomised controlled trial with 100 participants.
- Human research volume. 1 human study, 100 participants in total.
- What was measured. 1 human study measured a clinical or functional outcome rather than a laboratory marker alone.
- Replication. The supporting result has not been independently replicated in humans.
- Study duration. Longest human study ran 52 weeks.
Limitations. One trial at one dose in one population; it does not close the question, but it removes the strongest human claim spermidine marketing relied on.
| Study | Design | Population | Finding |
|---|---|---|---|
| [2]Effects of Spermidine Supplementation on Cognition and Biomarkers in Older Adult…JAMA network open · 2022 · PMID 35616942 | Randomised controlled trialHuman | 100 participantsParticipants with a diagnosed condition | Found no effectSmartAge: 12-month randomised trial; no significant memory benefit. |
Human evidence
2 studies in people.
- [1]Prospective cohort · 829 participants
- [2]Randomised controlled trial · 100 participants
Animal and laboratory evidence
Shown separately, and never used to support a human claim.
No preclinical study is currently linked on this page.
Before anything else
Safety and interactions
Supplemental doses appear well tolerated in trials to date, which have been small and no longer than a year or so. Long-term safety data does not exist.
The ledger
Grade history
No grade on this page has changed since tracking began. When one moves — a new trial, a retraction, a corrected appraisal — the change is detected automatically and recorded on the public ledger.
Falsifiability
What would change our view
Randomised trials showing functional or clinical benefits at achievable doses, replicated independently.
Check everything
Sources
Every citation links to its PubMed record. Bibliographic details are retrieved from PubMed, not written by us.
- [1]Higher spermidine intake is linked to lower mortality: a prospective population-based study Kiechl S et al.. The American journal of clinical nutrition. 2018. PMID 29955838 · doi:10.1093/ajcn/nqy102
- [2]Effects of Spermidine Supplementation on Cognition and Biomarkers in Older Adults With Subjective Cognitive Decline: A Randomized Clinical Trial Schwarz C et al.. JAMA network open. 2022. PMID 35616942 · doi:10.1001/jamanetworkopen.2022.13875