Spermidine vs NMN – Which Longevity Supplement Is Better for You?

Last updated: November 1, 2026 · Originally published: January 5, 2026 · By Eternal Elixir Editorial

Spermidine vs NMN is not a contest between two versions of the same thing. NMN (nicotinamide mononucleotide) is a building block your cells turn into NAD+, and several human trials show it raises blood NAD+. Spermidine is a polyamine studied mainly for autophagy, the cell’s recycling system, and most of that work is in animals. If you want one, NMN has more human evidence on its direct target. If you want both, our NMN 500mg and Spermidine 10mg come in 90-capsule bottles, and together they clear free shipping.

This guide compares the two on what each one does, what the human trials used and found, the doses and costs, and whether it makes sense to take NMN and spermidine together. We also answer the questions people search for most: whether spermidine is worth taking on its own, what not to take with it, the downsides of NMN, and which foods are high in spermidine.

Key numbers:

• 80 adults took 300 mg, 600 mg or 900 mg of NMN or placebo for 60 days in the largest dose-ranging NMN trial here. Blood NAD+ rose in every NMN group.
• 0.9 mg a day of spermidine from wheat germ extract for 12 months did not change memory against placebo in 100 older adults.
• 829 people in a population study who ate more spermidine had lower death rates over 20 years. That is an association, not proof that spermidine caused it.
• $0.67 and $0.56 a day for our NMN 500mg and Spermidine 10mg at one capsule each.

Spermidine vs NMN at a glance (as of Sep 2026)

Add NMN 500mg to cart · $59.99 Add Spermidine 10mg to cart · $49.99

Comparing NMN brands rather than ingredients? Our guide to the best NMN supplements in Australia compares them on cost per serve, and our round-up of the best spermidine supplements in Australia does the same for spermidine.

What spermidine is and what it does

Spermidine is a polyamine, a small molecule that every living cell makes and that you also eat. The spermidine supplement research centres on autophagy, the process that breaks down worn-out proteins and cell parts so their materials can be reused. Autophagy tends to slow with age, which is why spermidine sits in the longevity category.

What the animal work shows. In a 2016 study in Nature Medicine, Eisenberg and colleagues gave mice oral spermidine and found it extended their lifespan and preserved heart function in old animals. The heart benefit disappeared in mice whose heart cells couldn’t carry out autophagy. In 2024, Hofer and colleagues reported in Nature Cell Biology that spermidine levels rose during fasting in yeast, flies, mice and human volunteers, and that blocking spermidine production cut fasting-induced autophagy in yeast, worms and human cells and removed the lifespan benefit of fasting in animals. These are strong results in the lab. They are not evidence that a spermidine capsule extends human life.

What the human work shows. In a population study published in 2018, Kiechl and colleagues followed 829 adults aged 45 to 84 for 20 years. People in the top third for dietary spermidine had markedly lower death rates than those in the bottom third, and the link held after adjusting for lifestyle and other diet factors. Observational data like these can’t separate spermidine from everything else about a spermidine-rich diet.

The one long randomised trial is less encouraging. In the 12-month SmartAge trial (Schwarz and colleagues, 2022), 100 adults aged 60 to 90 who reported memory concerns took either 0.9 mg a day of spermidine from wheat germ extract or placebo. Memory performance did not change against placebo, and neither did the secondary outcomes. Exploratory analyses hinted at effects on inflammation and verbal memory, and the authors called for trials at higher doses. Adverse events were balanced between the groups.

Our capsule gives 10 mg of spermidine (as spermidine trihydrochloride), roughly eleven times the dose in that trial. That is a higher intake than the trials tested, not a proven one, and published human safety data at 10 mg a day are limited.

What NMN is and what it does

NMN is a direct precursor of NAD+ (nicotinamide adenine dinucleotide), a coenzyme that hundreds of enzymes use in energy metabolism. NAD+ levels fall with age in several tissues, and raising them is the idea behind NMN.

What the trials show. In the largest dose-ranging trial, Yi and colleagues (2023) gave 80 healthy middle-aged adults 300 mg, 600 mg or 900 mg of NMN, or placebo, once a day for 60 days. Blood NAD+ rose significantly in every NMN group, most at 600 mg and 900 mg. Six-minute walking distance improved more than placebo in all NMN groups, and no safety issues were found. Three of the authors work for the chemical companies Abinopharm and Aba Chemicals.

In older adults, Morifuji and colleagues (2024) gave 60 participants 250 mg a day of NMN or placebo for 12 weeks. The main outcome, a stepping test, showed no difference. Secondary outcomes did: the NMN group had higher blood NAD+, a shorter 4-metre walking time and better scores on a sleep quality questionnaire. Three of the four authors work for Meiji Holdings. A 2022 trial by Igarashi and colleagues gave older men 250 mg a day for 6 or 12 weeks and found higher blood NAD+ and small, nominal changes in gait speed and grip strength that the authors said need confirming.

On safety, Fukamizu and colleagues (2022) gave 31 healthy adults 1,250 mg of NMN a day for 4 weeks and found no changes beyond normal variation and no serious adverse events.

So NMN has the stronger human evidence for doing what it is meant to do, which is raising NAD+. Whether that translates into lasting benefits for ageing in people hasn’t been shown, and the trials run weeks to months, not years. Our capsule gives 500 mg, inside the 250 mg to 900 mg range the trials used. For a closer look at the NAD+ options, see our comparison of NMN vs NR as NAD+ precursors and our guide to NAD+ boosters.

Start with NMN 500mg · $59.99

Spermidine or NMN: which is better?

On the evidence as it stands, NMN is the better-supported choice if you take only one. Its human trials show it reaches its target, blood NAD+, at the doses on sale. Spermidine’s case rests mostly on animal studies and diet surveys, and its one long human trial found no effect at a low dose.

That doesn’t make spermidine pointless. It works on a different pathway, it’s the natural companion to fasting in the research, and it costs less per day. And neither compound has been shown to slow or undo human ageing. Anyone who says otherwise is going beyond the data.

Which should you choose?

Choose NMN if you want the compound with the most human trial data, you are interested in energy metabolism, or you are in your 40s or older, the ages most NMN trials enrolled. Take one capsule in the morning, as the label suggests.

Choose spermidine if your interest is the autophagy research, you already fast or eat within a time window, or you want the lower daily cost. Take one capsule with a meal.

Take both if you want to cover both pathways and are comfortable that the combination itself hasn’t been tested. A bottle of each costs $109.98 and ships free, and both last 90 days. Our Cellular Longevity Stack puts NMN 500mg, Spermidine 10mg and Trans-Pterostilbene 500mg in one order at $139.99. It already contains both, so buy it in place of the two single bottles rather than alongside them.

Can you take spermidine and NMN together?

People commonly take NMN and spermidine together, and there’s no known interaction between them. They act on different pathways and are taken at different times on the labels: NMN in the morning and spermidine with a meal. What doesn’t exist yet is a trial of the combination, so any claim that NMN and spermidine together work better than either alone is theory.

If you take both, start one at a time for a couple of weeks so you can tell how each suits you. Our guide to taking spermidine and NMN together covers timing in more detail, and our longevity stack guide shows how they fit with resveratrol and TUDCA. For a single capsule that pairs NMN with resveratrol, we also stock Vitasolutions NMN & Resveratrol 1100mg, and our comparison of pterostilbene vs resveratrol explains why our stack uses pterostilbene instead.

Is there a downside to taking NMN?

The trials above reported NMN as well tolerated at 250 mg to 900 mg a day for up to 12 weeks, and at 1,250 mg a day for 4 weeks, with no serious adverse events. The limits are length and scale: the longest trials here ran 12 weeks, and most enrolled 30 to 80 people. Long-term effects in people are unknown.

Cost is the other downside. NMN is dearer per day than many supplements, and the benefit you can measure is a blood marker. Talk to your doctor before starting if you are pregnant or breastfeeding, take prescription medicines, or have a medical condition.

What not to take with spermidine?

There’s no established list of medicines that interact with spermidine, and the 12-month trial reported adverse events at similar rates to placebo. That is different from saying it has been tested with everything. Our product page advises anyone pregnant, breastfeeding or taking medication to check with a healthcare professional first, and that’s the sensible rule for any supplement. Much of the spermidine research used wheat germ extract, so if you have a wheat allergy, check the source on any spermidine label before you buy.

Which food is highest in spermidine?

A food database compiled by Atiya Ali and colleagues at the Karolinska Institutet found spermidine highest in dried soybeans, chicken liver, green peas, corn, shellfish and blue cheese, with mushrooms also high in the data they collected. Wheat germ is the source of the spermidine extract used in the main human trials. Eating more of these foods is the cheapest way to raise your intake, and the population study above measured spermidine from food, not supplements.

Frequently asked questions

Is spermidine better than NMN?

Not on current human evidence. NMN has several randomised trials showing it raises blood NAD+ at 250 mg to 900 mg a day, while spermidine’s one long trial, at 0.9 mg a day, found no memory effect. If you choose one, choose NMN. Our NMN 500mg is 90 capsules for $59.99, or $0.67 a day.

Add NMN 500mg to cart · $59.99

Can I take NMN and spermidine together?

Yes. There’s no known interaction, and the labels suggest different times of day. The combination itself hasn’t been tested in a trial. Buying our NMN 500mg and Spermidine 10mg together comes to $109.98 with free shipping, or choose the Cellular Longevity Stack, which already includes both.

Add Spermidine 10mg to cart · $49.99

Can spermidine undo ageing?

No study has shown that in people. Spermidine extended lifespan in mice, and diets higher in spermidine are linked with lower death rates in population studies, but a link isn’t proof of cause and mouse results don’t carry over to humans.

Is there a downside to taking NMN?

Trials up to 12 weeks found it well tolerated, with no serious adverse events at up to 1,250 mg a day for 4 weeks. Long-term effects are unknown. Check with your doctor first if you are pregnant, breastfeeding or take prescription medicine.

What not to take with spermidine?

No specific interactions are established. If you take prescription medicines, are pregnant or breastfeeding, or have a wheat allergy (much of the research used wheat germ extract), talk to your doctor or pharmacist first.

Which food is highest in spermidine?

Dried soybeans, chicken liver, green peas, corn, shellfish and blue cheese are among the richest sources in published food data, and mushrooms are also high. Wheat germ is used to make the extract in the main spermidine trials.

What doses of NMN and spermidine were used in studies?

NMN trials used 250 mg to 900 mg a day, and one safety trial used 1,250 mg a day for 4 weeks. The main spermidine trial used 0.9 mg a day from wheat germ extract. Our capsules give 500 mg of NMN and 10 mg of spermidine, one capsule a day each.

How long before I notice anything?

In the Yi trial, blood NAD+ was already higher at day 30, and in the trials the walking and sleep measures changed by 60 days to 12 weeks. There’s no marker for spermidine you can check at home, and the 12-month trial found no memory change. Give either supplement at least one full 90-capsule bottle before judging it.

Which should I start with, NMN or spermidine?

Start with NMN if you want the one with more human data, or spermidine if you want the autophagy angle at a lower daily cost. Many people add the second after a few weeks on the first.

The verdict

If you take one: Eternal Elixir NMN 500mg. It has the stronger human evidence for reaching its target, and a 90-capsule bottle is $59.99, or $0.67 a day.

If you want the autophagy side as well: add Eternal Elixir Spermidine 10mg at $49.99 for 90 capsules. Know that its human evidence is thinner and that the trials used a much lower dose.

If you want a set: the Cellular Longevity Stack combines NMN 500mg, Spermidine 10mg and Trans-Pterostilbene 500mg for $139.99, shipped free from Sydney.

More reading

• Best NMN supplements in Australia, compared on cost per serve
• NMN supplement buyer’s guide for Australia
• Ca-AKG vs spermidine for autophagy
• Spermidine powder vs capsules
• Shop the full Eternal Elixir range

Sources

1. Yi L, Maier AB, Tao R, et al. The efficacy and safety of β-nicotinamide mononucleotide (NMN) supplementation in healthy middle-aged adults: a randomized, multicenter, double-blind, placebo-controlled, parallel-group, dose-dependent clinical trial. GeroScience. 2023;45(1):29-43. PubMed 36482258
2. Morifuji M, Higashi S, Ebihara S, Nagata M. Ingestion of β-nicotinamide mononucleotide increased blood NAD levels, maintained walking speed, and improved sleep quality in older adults in a double-blind randomized, placebo-controlled study. GeroScience. 2024;46(5):4671-4688. PubMed 38789831
3. Igarashi M, Nakagawa-Nagahama Y, Miura M, et al. Chronic nicotinamide mononucleotide supplementation elevates blood nicotinamide adenine dinucleotide levels and alters muscle function in healthy older men. NPJ Aging. 2022;8(1):5. PubMed 35927255
4. Fukamizu Y, Uchida Y, Shigekawa A, et al. Safety evaluation of β-nicotinamide mononucleotide oral administration in healthy adult men and women. Scientific Reports. 2022;12(1):14442. PubMed 36002548
5. Schwarz C, Benson GS, Horn N, et al. Effects of spermidine supplementation on cognition and biomarkers in older adults with subjective cognitive decline: a randomized clinical trial. JAMA Network Open. 2022;5(5):e2213875. PubMed 35616942
6. Kiechl S, Pechlaner R, Willeit P, et al. Higher spermidine intake is linked to lower mortality: a prospective population-based study. American Journal of Clinical Nutrition. 2018;108(2):371-380. PubMed 29955838
7. Eisenberg T, Abdellatif M, Schroeder S, et al. Cardioprotection and lifespan extension by the natural polyamine spermidine. Nature Medicine. 2016;22(12):1428-1438. PubMed 27841876
8. Hofer SJ, Daskalaki I, Bergmann M, et al. Spermidine is essential for fasting-mediated autophagy and longevity. Nature Cell Biology. 2024;26(9):1571-1584. PubMed 39117797
9. Atiya Ali M, Poortvliet E, Strömberg R, Yngve A. Polyamines in foods: development of a food database. Food & Nutrition Research. 2011;55. PubMed 21249159
10. Product pages read on 25 September 2026: NMN 500mg, Spermidine 10mg, Cellular Longevity Stack