Spermidine: why the longevity interest?

Spermidine has had a busy career for a molecule most people have never needed to pronounce. Your own cells make it. Wheat germ, soybeans, mushrooms and mature cheese contain it. Somewhere along the way it also picked up the nickname "fasting in a capsule". Let's find out how much of that reputation comes from people, how much from yeast and mice, and how much is just a good slogan.

Here is the scorecard so far. Lab and animal experiments tie spermidine to autophagy, the cell's recycling system. Some large food-diary studies find that people who eat more of it live longer. What is missing is the step in the middle: so far, the one 12-month randomised trial of a spermidine supplement in people with subjective memory worries (SmartAge) found no difference from placebo on its main memory test. That missing middle step is what this page is about.

What spermidine is and where it comes from

Spermidine is a polyamine, a small natural molecule found in living cells from bacteria to humans. Cells make it themselves, you get it from food, and gut microbes make some too (Yu and colleagues, 2025). One 2018 Science review describes it as already present in daily human nutrition (Madeo and colleagues).

That matters for how you read the headlines. Spermidine is not a foreign compound that a supplement introduces. The question is whether adding more, from food or a capsule, changes anything that matters for health.

Autophagy, minus the lecture

Autophagy is the cell's recycling system. A 2011 review in Cell describes it as the major route by which cell material is delivered to the lysosome and broken down, producing new building blocks and energy as well as clearing out what isn't needed (Mizushima and Komatsu). A tidy cell is a working cell, which is why researchers like to study it in ageing.

Here is how spermidine entered that story, in the order the experiments happened:

• 2009, yeast, flies, worms and human cells in a dish. Giving spermidine extended lifespan in yeast, flies and worms, and in cultured human immune cells. It also triggered autophagy, and autophagy turned out to be necessary for the lifespan effect (Eisenberg and colleagues).
• 2015, cultured human cells. Spermidine reduced the activity of an enzyme called EP300, which acts as a brake on autophagy. Taking the brake off is one proposed way it switches the process on (Pietrocola and colleagues).
• 2024, yeast, nematodes, mice, human cells and human volunteers. Spermidine levels rose during fasting and calorie restriction, and blocking the cell's own spermidine production weakened fasting-triggered autophagy and the lifespan benefits seen in the model organisms (Hofer and colleagues, Nature Cell Biology). This is where "fasting in a capsule" comes from.

That last result is the fun one, and it's worth reading precisely. It shows spermidine is part of how fasting switches autophagy on in those experiments. It does not show that swallowing spermidine reproduces fasting in a person. Autophagy is also hard to measure: the field's own guidelines say no single assay is perfect and that several methods are needed to monitor it properly (Klionsky and colleagues, 2021). So when a label says "activates autophagy", ask what was measured, in which organism, and at what dose.

Three layers of evidence, and what each can tell you

• Layer: Mechanism; What it looks like: Cells, yeast, worms, flies, mice; What it can tell you: Why researchers think spermidine might matter; What it can't: Whether a supplement helps a person
• Layer: Observational; What it looks like: Food questionnaires linked to health records; What it can tell you: Whether people who eat more spermidine-rich food tend to have different outcomes; What it can't: Whether spermidine itself is the reason
• Layer: Trials; What it looks like: Randomised, placebo-controlled studies of a supplement; What it can tell you: Whether a specific preparation changes a specific outcome; What it can't: Anything beyond the people, dose and time studied

Do spermidine-rich diets go with longer lives?

This is the evidence behind most longevity pitches, so it's worth a proper look.

The Bruneck study (Kiechl and colleagues, 2018). Researchers followed 829 adults aged 45 to 84 in South Tyrol, Italy. Diet was assessed by dietitian-administered food-frequency questionnaires in 1995, 2000, 2005 and 2010, with follow-up to 2015 and 341 deaths. Deaths per 1,000 person-years fell across thirds of spermidine intake, from 40.5 to 23.7 to 15.1. After adjusting for age, sex, lifestyle factors, established predictors of mortality and other dietary features, each standard-deviation increase in spermidine intake went with a hazard ratio of 0.76 for all-cause death (95% CI 0.67 to 0.86). The authors reported a similar result in a second cohort, the SAPHIR study, and compared the gap between the top and bottom thirds to being about 5.7 years younger (Kiechl and colleagues).

NHANES, United States (Wu and colleagues, 2022). Among 23,894 adults in surveys from 2003 to 2014, with 2,365 deaths, the highest quarter of dietary spermidine intake had hazard ratios of 0.70 for all-cause death and 0.68 for cardiovascular death compared with the lowest quarter (Wu and colleagues).

A prostate-cancer cohort (2026). In 54,517 men from the PLCO screening trial, dietary spermidine was not associated with prostate cancer incidence (relative risk 1.00 for top versus bottom fifth). The authors note that a possible inverse link with all-cause mortality may reflect residual confounding, and call the findings hypothesis-generating (Wang and colleagues).

Cognition. A 2025 review of 18 observational studies found mixed results: some linked higher spermidine to better cognition, others to worse outcomes. It also points out that food questionnaires may not reflect what ends up in the blood, and that spermidine measured in blood is tricky to interpret (Yu and colleagues).

How to weigh this? Our reading, which is editorial and not a finding from those papers: foods rich in spermidine, such as legumes, wholegrain products, vegetables, mushrooms and some cheeses, come bundled with fibre, other nutrients and, often, a certain style of eating. Researchers adjust for what they can measure, but a diet is a pattern, not a single ingredient. These studies make spermidine-rich eating look worth studying. They cannot tell you a capsule would copy the effect.

The supplement trials, one by one

Most human spermidine trials used a wheat-germ extract. They were small, short, and run mainly in older adults with memory concerns, so none of them can speak for a healthy 30-year-old.

• Trial: Wirth and colleagues, 2018; Who and how long: 30 adults aged 60 to 80 with subjective cognitive decline; 3 months; spermidine-rich plant extract versus placebo; Result: Moderately better memory-task performance with spermidine; the confidence interval for the between-group contrast just includes zero (-0.01 to 0.35). Described by the authors as a pilot; Ties and limits: Small pilot; effects judged by effect size (Cortex)
• Trial: Pekar and colleagues, 2021; Who and how long: 85 residents aged 60 to 96 in six nursing homes; 3 months; two spermidine doses; Result: Improved memory-test scores in the higher-dose group with mild dementia; authors call these first results of a preliminary study; Ties and limits: Early report; small subgroups (Wien Klin Wochenschr)
• Trial: SmartAge, Schwarz and colleagues, 2022; Who and how long: 100 adults aged 60 to 90 with subjective cognitive decline (51 spermidine, 49 placebo); 12 months; 750 mg wheat-germ extract giving about 0.9 mg spermidine a day; Result: No significant change in the primary memory outcome (difference -0.03, 95% CI -0.11 to 0.05, P=0.47) or in secondary outcomes; adverse events balanced between groups. Exploratory signals for verbal memory and inflammation need confirming; Ties and limits: The dose raised daily supply by only about 10 percent. Federal German research funding; the extract maker TLL The Longevity Labs provided funds for extract development, and several authors reported equity, advisory or executive roles there (JAMA Netw Open)
• Trial: Alsaleh and colleagues, 2026; Who and how long: 40 adults over 65 enrolled (results for 38) after a third COVID-19 vaccine dose; 6 mg spermidine daily for 13 weeks versus placebo; Result: Well tolerated. Among people who responded poorly to the vaccine, spermidine went with higher antibody and memory B-cell responses and signs of more autophagy in B cells; Ties and limits: Small pilot; the authors say its p-values are not meant as definitive evidence. Authors include consultants to TLL, which also contributed funding; the paper states TLL had no input into design, results or writing (Aging Cell)

Two other pieces are often quoted next to these. A Danish trial in older adults with coronary artery disease, POLYCAD, has so far published its study protocol only, which describes what will be tested, not what it found: 187 patients aged 65 and over randomised to 24 mg of spermidine a day or placebo for 48 weeks (Thorup and colleagues). And a 2026 review of the Alzheimer's evidence describes few, small and varied trials without consistent effects on their main cognitive endpoints (Angelucci and colleagues).

The dose gap is worth noticing. SmartAge used about 0.9 mg a day; the 2026 vaccine pilot used 6 mg. SmartAge's authors suggested a higher dose might be needed, and POLYCAD's protocol uses 24 mg a day. That keeps the question open, but only open: a null result at a low dose is not proof of benefit at a higher one.

Food or capsule? A portion-size reality check

If you mostly want spermidine, the obvious question is whether food already supplies a lot. A food-composition database assembled from published measurements gives portion estimates in milligrams (Atiya Ali and colleagues, 2011):

• Food (portion): Cooked soybeans (190 g); Spermidine per portion in that database: 9.7 mg
• Food (portion): Green peas (140 g); Spermidine per portion in that database: 9.1 mg
• Food (portion): Mushrooms (50 g); Spermidine per portion in that database: 4.4 mg
• Food (portion): Cheese (20 g); Spermidine per portion in that database: 2.0 mg

Put that beside the 0.9 mg in SmartAge's daily dose, which the authors say raised participants' daily supply by about 10 percent. A portion of peas, in this database, holds roughly ten times as much as that capsule dose. Peas, it turns out, have been quietly doing a lot of work.

A word on how firm those numbers are. They are averages built from papers that measured different samples in different countries, and the authors say cheese values varied considerably between studies. Spermidine content also depends on variety, storage and cooking, none of which this table captures. Your own absorption varies too, because gut bacteria both make and use polyamines (Yu and colleagues). Use the table to compare orders of magnitude, not to count milligrams.

Reading a spermidine label

A worked example from the EU rules: the authorised ingredient is a wheat-germ extract with a specification of 0.8 to 2.4 mg spermidine per gram of extract. SmartAge's 750 mg of extract therefore corresponds to roughly 0.6 to 1.8 mg of spermidine, which fits the 0.9 mg reported. That tells you what to look for:

• Spermidine per daily serving, not just extract weight. "500 mg wheat germ extract" and "3 mg spermidine" are different statements.
• Which source. Wheat-germ extract and other spermidine sources are different ingredients. The trials above mostly used wheat-germ extract, and the EU entry covers that extract only.
• Whether the dose matches a studied dose. If it doesn't, the trial results are about a different exposure.

Our guide to how to read supplement labels covers the general method.

Safety, medicines and who should wait

In SmartAge, adverse events were balanced between spermidine and placebo over 12 months. The 6 mg vaccine pilot reported good tolerability over 13 weeks. Those are reassuring but short, and they are in older adults under trial conditions. The EU authorisation applies to food supplements for adults, and no trial covers pregnancy, breastfeeding or children, so this is not a supplement for those groups on current evidence.

There is a reason for extra care around cancer. A 2025 review describes high rates of polyamine synthesis in both normal and malignant prostate tissue (Sena). The food-intake cohort above found no link between dietary spermidine and prostate cancer incidence, but eating spermidine-rich food and taking a concentrated supplement are not the same exposure. Our editorial advice is simple: if you have or have had cancer, or are in treatment, ask your oncology team before taking it.

Two more practical points that are our own cautions rather than trial findings. The extract comes from wheat germ, so anyone with a wheat allergy or coeliac disease should check with a pharmacist or doctor first. And none of the trials above was designed to answer interaction questions, so bring your medicines list to a pharmacist. Our page on supplements and medication explains what to ask.

Rules in the EU and the Netherlands (read on 8 October 2026)

The EU's Union list of novel foods includes "spermidine-rich wheat germ extract (Triticum aestivum)" for food supplements for the adult population, at up to the equivalent of 6 mg spermidine a day. The entry was first adopted in Implementing Regulation (EU) 2017/2470, and a March 2020 amendment changed one specification, the cadaverine limit (Regulation (EU) 2020/443). The company that notified this extract, TLL The Longevity Labs, is the same one named in the SmartAge disclosures above. The list is amended from time to time, so check the current consolidated version for newer changes.

The Netherlands applies EU novel-food law, and no separate Dutch rule on spermidine turned up. That covers the wheat-germ extract only; other spermidine ingredients may be treated differently. Law changes, so check the Commission's Novel Food Status Catalogue or the Dutch food authority (NVWA) before you buy.

Spermidine today: a good question, an unfinished answer

Spermidine has a real mechanism story and an unfinished human one. The mechanism work is real and consistent across organisms. The food studies hint at something, with the usual caveats. The one long supplement trial in people was negative on its main outcome, and the positive signals are small, early or exploratory.

For most readers, the practical takeaway is that the same foods linked to spermidine intake, beans, peas, whole grains, mushrooms, are worth eating anyway. A supplement is an optional extra rather than a shortcut. The news worth waiting for is a larger, longer, higher-dose trial with a clear primary result and funders independent of the extract's maker, plus the finished POLYCAD results.

Next reading: Smart Supplements 101 for a general decision framework.

Written by Smart Supplements with AI assistance from the sources linked in the text. It has not been reviewed by a clinician.

Last updated: 12 October 2026

This article is for informational purposes only and is not intended as medical advice. Always consult a healthcare professional before starting any new supplement, especially if you take prescription medication.