Spermidine
Summary
Spermidine supplements were well tolerated in small trials of 0.9–40 mg/day. A 12-month trial of a wheat germ extract in 100 older adults found no memory benefit, after an earlier 3-month pilot suggested one. Oral spermidine did not raise blood spermidine in a pharmacokinetic study; spermine rose instead.
Key facts
- Spermidine-rich wheat germ extract, rice germ extract, and high-purity spermidine trihydrochloride[1][6][3]
- No head-to-head human data between forms in our sources[3]
- Memory over 12 months: no change (C); memory in a 3-month pilot ↑ (D); safety markers at 40 mg/day: no change (D); blood spermidine: no rise, spermine ↑ (D)[1][2][3][4]
- Adverse events were balanced with placebo over 12 months at 0.9 mg/day; 40 mg/day for 28 days changed no clinical, lipid or blood-count measures[1][3]
- 4 graded human outcomes on this page
- October 9, 2026
How it works
ProposedSpermidine induces autophagy and protected against memory loss in aging model organisms (animal data). In people, a 15 mg/day study suggested oral spermidine is converted to spermine before reaching the blood, so any effects may partly come from spermine (proposed).[2][4]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Focus | Grade C | No effect | RCT · n = 100 · 2022 | 2 rows |
| Healthy aging | Grade D | No effect | RCT · n = 37 · 2024 | 2 rows |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Memory performance (mnemonic discrimination) | No effect | Grade C | RCT · n = 100 · 2022 Adults aged 60–90 with subjective cognitive decline (SmartAge trial) Form: Spermidine-rich wheat germ extract vs placebo · Dose: 0.9 mg spermidine/day · Duration: 12 months No significant change in memory performance or secondary outcomes versus placebo. Adverse events were balanced between groups. | 35616942 (opens PubMed)Source [1] |
| Safety and blood polyamines at a high amount | No effect | Grade D | RCT · n = 37 · 2024 Healthy men aged 50–70 Form: High-purity spermidine trihydrochloride vs placebo · Dose: 40 mg/day · Duration: 7 and 28 days No significant changes in clinical, lipid, chemistry or blood-count measures versus placebo and no product-related adverse events. Serum and urine polyamines did not change substantially. | 39405978 (opens PubMed)Source [3] |
| Memory performance in a pilot trial | Improved | Grade D | Pilot RCT · n = 30 · 2018 Cognitively intact adults aged 60–80 with subjective cognitive decline, described as at risk for Alzheimer's disease Form: Spermidine-rich plant extract vs placebo · Dose: Not stated in the abstract · Duration: 3 months Memory performance was moderately better than placebo (Cohen's d 0.77, confidence interval touching zero), and mnemonic discrimination improved in the spermidine group. | 30388439 (opens PubMed)Source [2] |
| Blood spermidine and spermine levels | Mixed | Grade D | Crossover RCT · n = 12 · 2023 Healthy volunteers Form: Spermidine vs placebo · Dose: 15 mg/day · Duration: 5 days per phase Plasma spermine rose versus placebo, but plasma spermidine and putrescine did not change, and saliva levels were unaffected. | 37111071 (opens PubMed)Source [4] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Spermidine-rich wheat germ extract | Varies[1][5] | No head-to-head human data[1] | Safety measures and self-reported health did not differ from placebo at 1.2 mg/day for 3 months; adverse events were balanced over 12 months.[5][1] | Memory in older adults |
| High-purity spermidine trihydrochloride | Varies[3] | 40 mg/day did not substantially change serum or urine polyamines over 28 days.[3] | No product-related adverse events at 40 mg/day for 28 days.[3] | Safety and polyamine levels |
| Spermidine-rich rice germ extract | Varies[6] | No head-to-head human data[6] | Clinical chemistry, blood counts, vital signs and adverse events reflected a good safety profile at 3.3 mg/day for 56 days in 12 adults.[6] | Blood markers of autophagy and heart health (uncontrolled pilot) |
Studied doses
Doses studied in human trials ranged from 0.9 to 40 mg of spermidine a day for 5 days to 12 months; most longer trials used about 1 mg/day from wheat germ extract.[1][3][4][5]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- High-amount products
- The only trial of 40 mg/day lasted 28 days in 37 healthy men, so longer-term safety at that amount is unknown.[3]
- Before you start
- Talk to your pharmacist or clinician before adding this supplement, especially if you take prescription medicines, are pregnant or breastfeeding, or have a chronic health condition.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Articles about Spermidine
Plain-English answers to common questions, built on the evidence above.
Frequently asked questions
Does spermidine improve memory?
A 3-month pilot of 30 older adults suggested a moderate benefit, but the 12-month follow-up trial in 100 older adults found no significant change in memory versus placebo.[2][1]
Does spermidine raise blood spermidine levels?
In a 5-day study at 15 mg/day, plasma spermidine did not rise but spermine did, suggesting conversion before it reaches the blood. A 28-day study at 40 mg/day also found no substantial change in polyamines.[4][3]
Sources
- [1]Effects of Spermidine Supplementation on Cognition and Biomarkers in Older Adults With Subjective Cognitive Decline: A Randomized Clinical Trial.. JAMA Netw Open, 2022. RCT
- [2]The effect of spermidine on memory performance in older adults at risk for dementia: A randomized controlled trial.. Cortex, 2018. pilot-RCT
- [3]Supplementation of spermidine at 40 mg/day has minimal effects on circulating polyamines: An exploratory double-blind randomized controlled trial in older men.. Nutr Res, 2024. RCT
- [4]High-Dose Spermidine Supplementation Does Not Increase Spermidine Levels in Blood Plasma and Saliva of Healthy Adults: A Randomized Placebo-Controlled Pharmacokinetic and Metabolomic Study.. Nutrients, 2023. crossover-RCT
- [5]Safety and tolerability of spermidine supplementation in mice and older adults with subjective cognitive decline.. Aging (Albany NY), 2018. RCT
- [6]Effects of Spermidine-Rich Rice Germ Extract Supplement on Biomarkers of Healthy Aging and Autophagy-Proof-of-Concept Pilot Study.. Altern Ther Health Med, 2025. open-label
What changed
- First draft. Every evidence-row PMID checked with NCBI E-utilities (esummary + efetch abstract) and re-read in an independent adversarial pass.