Spermidine

The verdict

Is Spermidine worth taking?

Spermidine has the best story in the longevity field and the widest gap between that story and what a capsule actually delivers. The gap is arithmetic, it is roughly tenfold, and nobody selling it reconciles the two numbers.

The claim. A 2018 Italian cohort of 829 people followed for twenty years found that higher dietary spermidine tracked with lower mortality — a hazard ratio of 0.76 per standard deviation, and a difference between the top and bottom third equivalent to being 5.7 years younger. That study is the foundation of the entire category. The top third of that cohort was eating roughly 11.6 mg of spermidine a day or more.

What is in the bottle. European law specifies the authorized wheat germ extract at 0.8 to 2.4 mg of spermidine per gram of extract. So an 800 mg serving — the standard dose on the leading products — contains somewhere between 0.6 and 1.9 mg. The labels say so. The "800 mg" on the front describes the extract, not the active. The legal maximum for a supplement in the EU and UK is 6 mg of spermidine a day, which is still only about half the intake the mortality finding rests on.

And the largest study found nothing. A Japanese cohort of 29,079 adults, followed 16 years, with 5,339 deaths — thirty-five times the size of the Italian study and sixteen times the deaths — found no association between spermidine intake and all-cause or cause-specific mortality in either sex. The authors wrote that their results "did not provide support for the notion that dietary spermidine has beneficial effects on mortality." That study is almost never cited in marketing.

And the best trial was null. One hundred older adults, twelve months, 0.9 mg a day: no effect on memory or biomarkers against placebo. The authors concluded that any benefit would need validating at higher dosage.

Emerging is the right grade, and the honest version of it is this: the biology is genuinely interesting, the epidemiology is contested rather than settled, and the supplement delivers about a tenth of the dose the epidemiology describes. If the dietary association is real, the way to act on it is food, not capsules — and the arithmetic below shows why that is not a stylistic preference.

What it does

What Spermidine does in the body

Autophagy induction (cellular self-cleaning), mitochondrial function support, anti-inflammatory activity, and cardiovascular and cognitive health support through polyamine-mediated cellular maintenance. Spermidine is a naturally occurring polyamine produced by all living cells and consumed in the diet primarily from wheat germ, mushrooms, soybeans, aged cheese, and fermented foods. Spermidine levels decline with age, and this decline is associated with reduced autophagy efficiency, a central pathway of biological aging.

The evidence

What the research actually shows

The epidemiology disagrees with itself, and the disagreement runs with study size.

The Bruneck study (Italy, n=829, 20 years, 341 deaths) found the headline result: all-cause mortality hazard ratio 0.76 per standard deviation of spermidine intake. A NHANES analysis and a Korean cohort found protective associations too. But the Takayama study (Japan, n=29,079, 16 years, 5,339 deaths) found nothing at all, and a UK Biobank analysis of 187,432 people found a non-linear relationship with the best mortality figure in the second quintile rather than the fifth. If the curve is an inverted U, then "more is better" is wrong on the epidemiology's own terms.

Where all of it is weakest: nobody measured what these people ate. Every one of these studies estimated spermidine intake by mapping a food questionnaire onto a polyamine composition table. The Italian study built its table from three prior sources — a 2011 literature compilation pooling published values from 1986 to 2009 across assorted countries, a US database, and a Japanese one. No Italian or Austrian food sample was ever analyzed for this purpose. The underlying per-food values rest on very small sample counts, and the 2011 compilation says outright that there is considerable variation between studies: it gives tomato putrescine anywhere from 1.2 to 122 mg/kg depending on whose paper you read.

The clearest demonstration that these tables are not interchangeable: estimates of average daily spermidine intake across published cohorts run from about 8 to about 55 mg a day, a sevenfold spread, including two separate figures for US adults that differ by a factor of seven. At least one of them is badly wrong, and nothing in the literature says which.

The trials, in order of how much weight they can carry.

The only adequately powered, placebo-controlled, long trial is SmartAge: 100 adults aged 60 to 90 with subjective cognitive decline, 0.9 mg of spermidine a day in 750 mg of wheat germ extract, twelve months. The primary outcome was a memory task. The between-group difference was −0.03 (95% CI −0.11 to 0.05), P = 0.47. Nothing moved. The product was supplied by the manufacturer.

Before it, the same group ran two three-month studies at about 1.2 mg a day in around 30 people each. One reported a moderate memory improvement; the other, a safety study, found that blood polyamine levels did not differ between the supplemented and placebo groups at follow-up. A further pair of Austrian nursing-home studies reported cognitive gains, but one had two active arms and no placebo at all and the other was open-label with no control group — in a dementia population over a year, neither can be interpreted.

Seven of the ten trials I could find involved the manufacturer, and several of the senior authors in this field hold or have held financial interests in the company that supplies the extract. That does not make the work wrong. It does mean the independent studies deserve extra weight, and the two cleanest ones are the two that found nothing.

The arithmetic

A capsule is about one milligram

This is the number that decides whether the rest of the page matters.

Source	Spermidine, mg/day	Note
Typical supplement, 800 mg wheat germ extract	0.6 – 1.9	EU specification for the authorized extract
EU and UK legal maximum per day	6	Adults only, excluding pregnant and lactating women
Bruneck top third — the group with the mortality finding	over 11.6	The intake the longevity claim describes
Japanese population average (Takayama)	about 14	Achieved by ordinary eating, and associated with no mortality benefit
Wheat germ, 30 g — two heaped tablespoons	about 11 – 13	Two independent measurements of wheat germ agree within 25%
Natto, 50 g	about 13	Fermentation raises spermidine about 41% over steamed soybeans

To reach the intake the mortality association describes using the leading supplement, you would need somewhere around eight grams of extract a day — about twenty capsules. Two heaped tablespoons of plain wheat germ gets you there, and so does a small bowl of natto. That calculation is mine, but every figure in it comes from the table above.

Worth noticing how little concentrating the extract actually does. Wheat germ itself runs around 35 to 44 mg of spermidine per 100 g. The authorized extract made from it is specified at 0.8 to 2.4 mg per gram — that is 80 to 240 mg per 100 g, so roughly two to five times the raw material by weight, in a capsule you take 800 mg of rather than 30 g of. The concentration step is real and the serving size undoes it.

None of this means the labels are lying. They are not: the good ones print the actual spermidine content in milligrams, and it is about 1 mg. The problem is that "800 mg" is the number on the front of the bottle and 1 mg is the number that matches the research, and almost nobody puts those two side by side.

One honest caveat on the other side. A single independent analysis of nine products found most of them landing where their labels said, and two coming in below the EU minimum specification — one of them about tenfold below. That was one commercial lab, the analytical method was not published, and it has not been replicated, so treat it as a reason to buy from someone who publishes a certificate of analysis rather than as a verdict on any particular brand.

Worth checking

What reaches your blood is spermine, not spermidine

Four independent human studies have measured what happens to blood spermidine when you swallow spermidine. All four found essentially nothing, across a thirtyfold dose range.

1.2 mg a day for three months: no difference between supplemented and placebo groups. Fourteen milligrams a day from natto for twelve months: spermidine did not increase in either group. Fifteen milligrams a day for five days, in an independently funded crossover trial with no declared conflicts: plasma spermidine unchanged, no change in any of 39 metabolites or 112 lipoprotein parameters. And 40 milligrams a day of purified spermidine for 28 days — forty times a typical capsule — moved serum spermidine from 0.169 to 0.174 micromolar, with an interaction p-value of 0.92.

What did rise in two of those studies was spermine. The reading the investigators themselves give is that dietary spermidine is converted before it reaches the circulation — in the gut wall and the liver — so that what enters the bloodstream is largely a different polyamine. One group put it plainly: it is rather unlikely that spermidine supplements below 15 mg a day exert any short-term effects.

This matters for two reasons. First, it undercuts the simplest version of the mechanism, because the autophagy effects demonstrated in cell culture occur at 10 to 100 micromolar and human serum sits around 0.2 micromolar — two to three orders of magnitude lower, and not moving. Second, it matters for the safety section below, because spermine is the one polyamine that has shown up on the wrong side in human cancer data.

The single human study to measure autophagy after oral spermidine found increased flux in B cells only, at two weeks, at 6 mg a day, in 40 people, as a secondary observation in a trial whose actual endpoint was safety. The authors say a larger sample is needed to confirm it. That is the entire human evidence that this compound does in people what it does in yeast.

Stated carefully

The cancer question, and why it is not a scare story

Polyamines are required for cells to divide. Depleting them is an active cancer therapy strategy. That makes the question of whether to supplement one of them a fair one to ask, and the honest answer is mixed rather than alarming.

The directly relevant human study found harm. In 1,164 people pooled from the control arms of two randomized trials, all of whom had already had a colorectal adenoma removed, above-median dietary polyamine intake was associated with a 39 percent higher risk of a new adenoma at follow-up (adjusted odds ratio 1.39, 95% CI 1.06 to 1.83). That is the closest anyone has come to asking whether dietary polyamines matter in someone who already has a precancerous lesion, and the answer was unfavorable.

A second signal, in the largest cohort. The Japanese study that found no mortality benefit did find a suggestive positive association between spermidine intake and cancer mortality in women — hazard ratio 1.38 for the highest against the lowest quartile, with a trend p-value of 0.02. The authors flag it as unexpected and contrary to the animal literature.

And a signal in the other direction. In 87,602 postmenopausal women followed for over twelve years, no positive association between polyamine intake and colorectal cancer appeared at all. A large case-control study found dietary spermidine protective and spermine associated with increased risk — which is worth sitting with, given that oral spermidine appears to arrive in the circulation largely as spermine.

What to take from this. For a healthy adult eating a normal diet, nothing here is a reason to avoid wheat germ or mushrooms or natto; the foods carrying spermidine are the foods everyone agrees are worth eating, and no study has ever found harm from them. The caution attaches to concentrated supplementation in someone with a history of colorectal adenomas or an active cancer, where the only directly relevant human evidence points the wrong way and there is no supplement trial at all in that population. That is a conversation with an oncologist, not with a label.

Otherwise, short-term tolerability is well documented: 40 mg a day of purified spermidine for 28 days produced no product-related adverse events and no meaningful change in blood chemistry, and twelve months at 0.9 mg a day produced no imbalance in serious events against placebo. Beyond about twelve months, in humans, there is no safety data at all.

Two practical notes that marketing leaves out. The authorized supplement is for adults only and explicitly excludes pregnant and lactating women. And wheat germ products are not gluten-free — the leading ones declare gluten in the daily dose, which matters if you have celiac disease.

Food first

Getting Spermidine from food

This is the one compound in the guide where food first is not a preference, it is the only route that reaches the dose the research describes.

Food	Spermidine, mg per 100 g	Note
Wheat germ	35 – 44	Two independent measurements, 25% apart. The most consistent high source
Natto	about 26	Fermenting steamed soybeans raises spermidine about 41%
Soybeans, dried or raw	3 – 20	A sixfold spread across three studies. Treat with caution
Cheddar, matured one year	about 20	But see the note below — aged cheese is not reliable
Mushrooms	9 – 13	Two sources, 45% apart
Green peas	4 – 5
Chickpeas	about 3
Pork liver, roasted	about 5	The highest of the meats measured
Chicken breast, roasted	about 3
Whole grain bread	1 – 2
Beef, cooked	0.4 – 0.7
Gouda, 16 months	not detected	Same category as the Cheddar above

Read that table with its disagreements showing. Soybeans run from 3 to 20 mg per 100 g depending on whose paper you read. Lentils differ by a factor of five to twelve between studies. And aged cheese is incoherent: matured Cheddar measures around 20 mg per 100 g while sixteen-month Gouda came back as not detected, with hard-ripened cheeses generally sitting near the bottom. The widely repeated claim that aged cheese is rich in spermidine rests on Cheddar and does not generalize. What dominates fermented dairy is putrescine, a different polyamine. Wheat germ is the one entry two labs agree on, and natto is the one dish that delivers a research-level dose in a normal serving.

Cooking changes this more than almost anything else in the guide, and the direction is useful.

• Boiling loses up to 64 percent — but it is leaching, not destruction. About 94 percent of what leaves the food is recovered in the cooking water. Chard, spinach, zucchini, pork and beef are worst affected. Keep the pot liquor and you keep the polyamines.
• Grilling loses over 20 percent, and this one is genuine chemical destruction rather than leaching — the Maillard reaction consumes the amino groups that make a polyamine a polyamine. The same browning that makes the crust eats the compound.
• Microwaving loses significantly less than either.
• Sous-vide showed no significant loss in any food tested. It is the best-preserving method measured, which is the kind of thing worth knowing if you already cook that way.
• Fermentation adds. Turning steamed soybeans into natto with Bacillus subtilis raised spermidine by about 41 percent while reducing spermine.

No data exists on storage or shelf life, so nobody knows what a bag of wheat germ open in a cupboard for three months is worth.

The practical version. Two heaped tablespoons of wheat germ, stirred into something rather than cooked hard, or a 50 g serving of natto, puts you at or above the intake the entire longevity literature is built on — for pennies, and without the dose gap. Whether that does anything for how long you live is a separate question, and the largest study to ask it said no. But if you are going to act on this compound at all, that is how.

What the guide adds

The part that is not on this page

Everything above is the assessment. What the guide adds for Spermidine is the protocol:

• Optimal Form
• Bioavailability
• Purity Red Flags
• Stack With / Avoid

147 entries across nine categories, every one graded against the clinical literature the same way.

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About the author

Who graded this

Daniel Edlund is a Le Cordon Bleu-trained private chef in Los Angeles, a certified personal trainer and strength coach, and an internationally licensed massage therapist. Thirty years of strength training and fifteen years cooking in private estate kitchens. He is the author of The Complete Supplement Guide, which grades 147 entries against the clinical literature, and of The EASY Way to Organic Cooking, first published in 2013.

More about Daniel →

This page is information, not medical advice. Supplements interact with prescription medication and with each other, and the right answer depends on your own bloodwork and history. Talk to your doctor before starting anything, particularly if you are pregnant, nursing, managing a health condition, or already taking medication.

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