Spermidine

Not a peptide. Spermidine is a polyamine — a small organic molecule with three amine groups, made in the body from the amino acid ornithine and also obtained from food. It is included because it is constantly discussed alongside peptides in longevity protocols and people search for it here. The same evidence standards apply.

N-(3-aminopropyl)-1,4-butanediamine; a polyamine alongside putrescine and spermine; wheat-germ extract is the usual supplement source

Longevity & cellular

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Summary

Class: Naturally occurring polyamine; present in all cells and in many foods (wheat germ, soybeans and natto, aged cheese, mushrooms, legumes). Supplements are usually wheat-germ extract standardised for spermidine, or synthetic spermidine trihydrochloride
Mechanism: Induces autophagy — the cell's recycling of damaged proteins and organelles — mainly by inhibiting the acetyltransferase EP300; also stabilises DNA and RNA, supports protein translation via hypusination of eIF5A, and has anti-inflammatory and cardioprotective effects in animals
Routes studied: Oral (human trials and epidemiology); drinking water or diet (rodents); culture medium (yeast, worms, flies, human cells). No injectable use of any note
Dose range reported: Human RCTs: 0.9–1.2 mg/day spermidine from wheat-germ extract for 3–12 months; a few studies up to ~6 mg/day. Typical dietary intake: roughly 10–15 mg/day in Western diets, higher in Mediterranean and Japanese diets. Community-reported: 1–10 mg/day from supplements, sometimes with high-polyamine foods
Half-life: Not meaningfully defined; dietary spermidine is absorbed in the small intestine, enters a body pool that is tightly regulated, and is also produced by gut bacteria. Blood levels respond slowly to intake
Storage: Capsules or powder: cool, dry, away from light. Wheat-germ extracts are food products and keep for the labelled shelf life
Regulatory status: A food constituent and supplement ingredient, not a medicine, in all regions. See region table

Doses are as reported in studies or by the community — never recommendations.

1What it is

Spermidine was named in the 1920s after the fluid it was first isolated from, but it is in every cell of every organism, where it binds and stabilises DNA and RNA, supports cell growth and helps make proteins. Levels in tissue fall with age in most species studied, including humans. Interest in it as a longevity compound dates from a 2009 paper showing that adding spermidine to yeast, worms, flies and human immune cells extended their lifespan by triggering autophagy (Eisenberg 2009, Nat Cell Biol), followed in 2016 by a mouse study showing longer life and better heart function with spermidine in drinking water, together with epidemiological data linking dietary spermidine to lower blood pressure and heart disease in people (Eisenberg 2016, Nat Med).

It is eaten in gram-free, milligram amounts every day — a bowl of natto or a serving of aged cheese contains more than most supplements — and supplements are mostly concentrated wheat-germ extract. That makes it one of the most benign compounds on this site to discuss, and also one where the gap between enthusiastic marketing and the small, mixed human trials deserves to be stated.

2How it's thought to work

Autophagy induction. Spermidine inhibits EP300, an acetyltransferase that normally restrains autophagy, and reduces acetylation of autophagy-related proteins; the net effect is more clearance of damaged mitochondria and protein aggregates (Pietrocola 2015). This is the mechanism behind lifespan extension in model organisms and is abolished when autophagy genes are deleted.

Translation. Spermidine is the only source of the unusual amino acid hypusine in eIF5A, a translation factor needed for making certain mitochondrial and autophagy proteins; this links polyamine levels to immune cell function and ageing (Puleston 2019; Zhang 2019).

Cardiovascular. In old mice, dietary spermidine improved diastolic heart function, reduced cardiac hypertrophy and lowered blood pressure in a salt-sensitive rat model, with autophagy and improved mitochondrial function in heart muscle as the proposed route (Eisenberg 2016).

Anti-inflammatory and anti-oxidative. Reduced inflammatory cytokines and oxidative damage in animal and cell models; some effect on gut barrier and microbiome composition.

Hair and skin. Polyamines prolong the growth phase of hair follicles in culture (Ramot 2011), the basis of topical and oral hair products.

A polyamine from food rather than a peptide, reaching the same end point as mTOR inhibition by a different route: it inhibits EP300 and induces autophagy. Most of the human evidence is observational, from dietary intake rather than supplementation.Schematic — not to scale

3What the research shows

Lifespan and healthspan in model organisms

Reproducible lifespan extension in yeast, worms, flies and mice with dietary spermidine, dependent on autophagy (Eisenberg 2009, 2016). Mouse cardioprotection and reduced age-related hypertrophy are the most clinically suggestive animal findings. [1][2]

Graded B (observational)

Dietary intake and mortality in humans

In the Bruneck prospective cohort (n=829, 20-year follow-up), higher dietary spermidine intake was associated with lower all-cause mortality, with the top third of intake corresponding to roughly five years' lower mortality risk after adjustment (Kiechl 2018, Am J Clin Nutr). Observational; spermidine-rich diets are also whole-food, plant- and fermented-food diets. [4]

Graded A (negative on primary endpoint)

Memory and cognition in older adults

The SmartAge pilot (n=30, 3 months, ~1.2 mg/day wheat-germ extract) suggested improved memory performance (Wirth 2018, Cortex). The full SmartAge trial (n=100, 12 months, 0.9 mg/day) found no significant difference from placebo on the primary memory outcome, though it was safe and well tolerated (Schwarz 2022, JAMA Netw Open). A smaller nursing-home study reported improved cognitive test scores over 3 months (Pekar 2021, Wien Klin Wochenschr). The best-designed trial is null; the dose used may be below what animal work would predict. [5][6][7]

Cardiovascular and blood pressure in humans

Observational associations with lower blood pressure and cardiovascular events (Eisenberg 2016 human cohort data). No with cardiovascular outcomes. [2]

Graded B/C

Hair growth

A small industry-involved RCT of an oral spermidine-based supplement (2017) reported a modest increase in the proportion of hairs in the growth phase in healthy adults, and ex-vivo human follicle studies show prolonged anagen (Ramot 2011). Small; not independently replicated. [10]

Graded C/B

Immunity, vaccine response, infection

Spermidine restored autophagy and vaccine responses in B cells from older donors (Zhang 2019), and improved T-cell function in old mice. A small human trial in COVID-era immune ageing was proposed; no robust outcome data †. [8]

4Reported side effects and interactions

Literature-reported

Spermidine supplementation at 0.9–1.2 mg/day for up to 12 months in older adults was safe and well tolerated, with adverse events no different from placebo (Schwarz 2022). Higher doses have only short-term data. Dietary intake far above supplement doses is normal in several populations.

Community-reported

occasional mild gastrointestinal upset or bloating from wheat-germ extracts (gluten-containing unless specified), rare headache. Most users report no acute effects at all, which is expected for a compound acting over months.

Theoretical. polyamines are needed by rapidly dividing cells, and cancer cells upregulate polyamine synthesis — polyamine-synthesis inhibitors (DFMO/eflornithine) are used in oncology, and polyamine-restricted diets have been studied in cancer patients. People with active cancer or a recent cancer history should discuss supplementation with their oncologist; the epidemiology (lower cancer mortality with higher intake) and the theory point in opposite directions and are unresolved. Autophagy induction is likewise double-edged in established tumours. Wheat-germ products contain gluten (relevant for coeliac disease) and may be high in histamine-related compounds.

Interactions. none established. In theory additive with other autophagy inducers (fasting, rapamycin, metformin); clinically unstudied.

Markers researchers commonly monitor

No compound-specific clinical markers are established; whole-blood polyamine levels are research assays. Reasonable choices for anyone taking it long term:

Marker	Why it's watched
Blood pressure	the most consistent human association and the mouse cardiovascular finding; cheap to track.
Lipid panel, fasting glucose, HbA1c	general cardiometabolic outcomes that the epidemiology suggests might shift over years; realistically a baseline for context.
A repeatable cognitive test	if memory is the goal, given the SmartAge result, a baseline is the only way to see whether anything happens.
hs-CRP	a general inflammation marker; spermidine is anti-inflammatory in animals.
For anyone with a cancer history, whatever surveillance their oncologist already runs	because of the polyamine–proliferation question; this is a conversation with a clinician, not a self-test.
CBC and CMP	general baseline.

Free for everyone. Safety information is never behind a paywall.

5Formulation and handling

Oral only. Supplements are wheat-germ extract capsules standardised to about 0.8–1.5 mg spermidine per capsule, or less commonly synthetic spermidine trihydrochloride at 1–10 mg. Label claims for extract products refer to spermidine content, not total polyamines; check which. Food sources (natto, wheat germ, aged cheese, mushrooms, legumes, whole grains) deliver comparable or higher amounts and were what the epidemiology measured. Store cool and dry. There is nothing to and the calculator is not relevant.

6Commonly studied alongside

NAD+ and its precursors (#99) in longevity protocols; resveratrol, fisetin and quercetin as "senolytic/sirtuin" companions (community); fasting and time-restricted eating (as another autophagy trigger); in peptide-community stacks, Epitalon, MOTS-c and SS-31. No combination has human outcome data.

Informational cross-links. Not stack recommendations.

7Regulatory status by region

Region	Status (checked —)
United States	Food constituent; sold as a dietary supplement (wheat-germ extract and synthetic spermidine). Not FDA-approved as a drug, and no drug application is pending to our knowledge
European Union	Spermidine-rich wheat-germ extract is marketed as a food supplement; a specific wheat-germ extract has novel-food authorisation and synthetic spermidine has been assessed for novel-food status †
United Kingdom	As EU (retained novel-food framework) †
Australia	Available as a listed complementary medicine ingredient / food supplement †
South Africa	Available as a supplement; no specific status
Sport (WADA)	Not prohibited

8Open questions

Is ~1 mg/day from a supplement meaningful on top of a 10–15 mg/day dietary intake, or do only dietary patterns matter?
Do higher supplement doses (5–10 mg/day) do anything the SmartAge dose did not? No long-term trial.
Cardiovascular outcome trial — none exists.
The cancer question: does raising polyamine intake carry risk in people with occult or treated tumours?
How much of the benefit in epidemiology is spermidine versus the foods that contain it.

9References

1Eisenberg T et al. (2009). Induction of autophagy by spermidine promotes longevity. Nat Cell Biol. PubMed · DOI
2Eisenberg T et al. (2016). Cardioprotection and lifespan extension by the natural polyamine spermidine. Nat Med. PubMed · DOI
3Pietrocola F et al. (2015). Spermidine induces autophagy by inhibiting the acetyltransferase EP300. Cell Death Differ. PubMed · DOI
4Kiechl S et al. (2018). Higher spermidine intake is linked to lower mortality: a prospective population-based study. Am J Clin Nutr. PubMed · DOI
5Wirth M et al. (2018). The effect of spermidine on memory performance in older adults at risk for dementia: a randomized controlled trial. Cortex. PubMed · DOI
6Schwarz C et al. (2022). Effects of spermidine supplementation on cognition and biomarkers in older adults with subjective cognitive decline: a randomized clinical trial. JAMA Netw Open. PubMed · DOI
7Pekar T et al. (2021). The positive effect of spermidine in older adults suffering from dementia: first results of a 3-month trial. Wien Klin Wochenschr. PubMed · DOI
8Zhang H et al. (2019). Polyamines control eIF5A hypusination, TFEB translation, and autophagy to reverse B cell senescence. Mol Cell. PubMed · DOI
9Madeo F et al. (2018). Spermidine in health and disease. Science. PubMed · DOI
10Ramot Y et al. (2011). Spermidine promotes human hair growth and is a novel modulator of human epithelial stem cell functions. PLoS One. PubMed · DOI

† Being confirmed by our reviewers against current sources.

10Community

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11Page history

26 Oct 2026Profile published — awaiting medical review

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