Kitchen scale beside bowls of wheat germ, green peas, mushrooms, soybeans and a pear on a sunlit table
October 09, 2026

How Much Spermidine Per Day? Doses Used in Studies

By SciRouter Editorial Team · Last reviewed: 9 October 2026

There is no official recommended daily amount of spermidine[1]. Estimates of what people eat from food run from about 5 to 15 mg a day[1]. Human studies have given about 0.9 to 40 mg a day[2, 3]. The only year-long placebo-controlled trial used the lowest dose and found no significant effect on its main outcome[2].

This page separates three numbers that are easy to mix up: what food provides, what trials tested and what labels say. For the wider evidence, see our guide to what the science shows about spermidine supplements.

How we researched this. Our searches ran on 8 October 2026 in PubMed, through NCBI E-utilities, and we read open full text on Europe PMC where it existed. We also checked agency pages from the UK Food Standards Agency, the US FDA, Health Canada and EFSA. We put human trials first, labelled animal studies by species, and cited only sources we opened and checked against PubMed or the agency page. We flag studies linked to an ingredient maker. This page cites 30 sources. It is not medical advice.

How much spermidine do people get from food?

Most published estimates fall between about 5 and 15 mg of spermidine a day, depending on the country and the method[1]. Two recent studies, one of more than 168,000 UK adults, put average or median intake at about 10.5 to 11.5 mg a day[4, 5].

Who was studied How intake was estimated Spermidine per day Source
UK Biobank, 168,137 adults 24-hour diet questionnaires Average 10.5 mg [4]
184 older Danish adults with coronary artery disease Food-frequency questionnaire Median 11.5 mg [5]
93 Swedish teenagers 7-day weighed food records About 9.6 mg [6]
165 US adults aged 40 to 80 with past colorectal polyps Food-frequency questionnaire About 7.9 mg [7]
Spain, by age group National food data About 4.6 mg (under 35) to 13.4 mg (over 65) [8]
Turkey National food data About 4.8 mg [9]
Model diets (Swedish advice; Mediterranean) Diet modelling About 25 to 30 mg; about 28 mg [6, 8]
  • Plants supply most of it. Spermidine is the leading polyamine in plant foods[1]. In Spain, vegetables were the largest single source, at about a third of intake[8].
  • Rich sources include wheat germ, soybeans, natto and mushrooms[10, 11]. Our table of spermidine content by food gives values in mg per 100 g.

What doses did human spermidine studies use?

Human studies gave between about 0.9 and 40 mg of spermidine a day[2, 3]. Most were small or short, and only the lowest dose was tested against placebo for a full year[2].

Study People (n) Daily spermidine and form Length What was found
SmartAge, 2022[2] Older adults with self-reported memory decline (100) About 0.9 mg, wheat germ extract 12 months No significant effect on the main memory measure; blood polyamines unchanged; side effects similar to placebo
Pilot trial, 2018[12, 13] Older adults with self-reported memory decline (30) 1.2 mg, wheat germ extract 3 months Blood tests no different from placebo; memory effect uncertain (confidence interval included zero)
Bread rolls, 2021[14] Nursing-home residents (92; 85 tested) 3.3 or 1.9 mg per roll, 6 rolls a week 3 months No placebo; test scores rose in both groups; blood spermidine rose with 3.3 mg rolls only
Follow-up, 2024[15] Nursing-home residents (45) At least 3.3 mg in the diet 1 year No control group; median 5-point rise on a cognitive screening test
Rice germ pilot, 2025[16] Healthy adults (12) 1.5 or 3.3 mg, rice germ extract 8 weeks No placebo; some blood markers linked to autophagy changed from baseline at 3.3 mg
Immune pilot, 2026[17] Adults over 65 (40) 6 mg, wheat germ extract 13 weeks Well tolerated, the main outcome; exploratory immune findings
Natto diet, 2021[18] Healthy men (57; 30 ate natto) About 14 mg extra, from natto 12 months Not randomized; blood spermine rose, blood spermidine did not
Blood-level study, 2023[19] Healthy adults (12) 15 mg, chlorella and soy capsules 5 days Blood spermine rose, blood spermidine did not
Safety trial, 2024[3] Healthy men aged 50 to 70 (37) 40 mg, spermidine trihydrochloride 28 days No significant change in routine blood tests; no product-related side effects
Hair trial, 2017[20] Healthy adults (100) Not reported 90 days Maker-funded; more hair follicles in the growth phase than placebo
Spermidine per day in diets and in human studies Log-scale chart. Diets supply about 5 to 15 mg a day. Studies gave 0.9 mg for 12 months, 1.2 mg for 3 months, 1.5 to 3.3 mg for 8 weeks, 6 mg for 13 weeks, 15 mg for 5 days and 40 mg for 28 days.6 mg: GB cap, one extractTypical diets5–15 mgSmartAge, 12 months0.9 mgPilot, 3 months1.2 mgRice germ, 8 weeks1.5–3.3 mgImmune pilot, 13 weeks6 mgBlood-level study, 5 days15 mgSafety trial, 28 days40 mg0.5125102050mg of spermidine per day (log scale)
Daily spermidine in typical diets and in human studies. Diet range[1]; study doses[2, 3, 12, 16, 17, 19]; Great Britain cap[21]. On a small screen, scroll the figure sideways.

How to read the table:

  • Terms. In a randomized trial, chance decides who gets the supplement and who gets a placebo, a dummy pill. A 95% confidence interval shows the spread of results the data are consistent with; when it spans zero, the study cannot rule out no effect.
  • Industry links. SmartAge, the 2018 trial and the 2026 pilot all used wheat germ extract supplied by its maker, and some of their authors had equity or consulting ties to that company[2, 12, 17]. The 2026 authors say it had no input into their design or analysis[17]. Two authors of the 40 mg trial worked for the ingredient's maker, and the rest received its funding[3].
  • Design. The two studies that compared doses had no placebo group[14, 16].

What happened at 15 mg and 40 mg a day?

Neither high dose clearly raised blood spermidine[3, 19]. At 15 mg a day for 5 days, blood spermine rose but blood spermidine did not, and 40 mg a day for 28 days changed blood and urine polyamines little[3, 19].

The 15 mg study was a crossover trial in 12 healthy adults: each person took spermidine for 5 days and a placebo for 5 days, in turn[19]. The dose was ten 1.5 mg capsules a day[19]. Spermine, a related polyamine, rose in the blood, while spermidine, putrescine and saliva levels did not change[19]. The authors suggested the gut lining or liver turns spermidine into spermine before it reaches the blood[19].

They also wrote that doses below 15 mg a day are unlikely to have short-term effects[19]. That was their reading of blood levels, not a tested health result[19]. It does not show that higher doses help.

The 40 mg trial, in 37 men aged 50 to 70, found no significant change in routine blood tests and no product-related side effects, but it lasted only 28 days[3].

Salt or spermidine: what does "40 mg" mean?

Spermidine trihydrochloride, also written spermidine-3HCl, is a purified salt form[3, 22]. The 40 mg trial's abstract does not say whether 40 mg counts the whole salt or only the spermidine in it[3]. If a dose counts the salt, it holds less spermidine than the number suggests.

Does a bigger dose raise blood spermidine?

Mostly not. In the intervention studies that reported it, extra spermidine from capsules or food left blood spermidine largely unchanged, and bread rolls were the one exception[2, 3, 14, 18, 19].

  • Capsules. Blood polyamines did not change after 12 months at 0.9 mg a day or 3 months at 1.2 mg a day[2, 12].
  • Natto. About 14 mg extra a day for 12 months raised blood spermine a little, but not blood spermidine[18].
  • Bread rolls. Median blood spermidine rose from 41.65 to 59.40 ng/ml with the 3.3 mg rolls, but not with the 1.9 mg rolls[14].
  • Everyday diets. In older Danish adults, doubling food intake was linked to only 18% higher blood spermidine, and not to muscle levels[5].

Blood levels may be a poor guide anyway. The SmartAge authors noted that tissues probably take up polyamines from the blood quickly[2].

Is 6 mg a day an official limit?

No. The 6 mg figure is a condition of use for one ingredient, spermidine-rich wheat germ extract, in adult supplements in Great Britain[21].

The UK Food Standards Agency register lists this extract for food supplements "intended for the adult population, excluding pregnant and lactating women"[21]. The limit reads "equivalent of max. 6 mg/day spermidine"[21]. Its legal basis is EU-era rules from 2017 and 2018[21]. We could not open the EU's own legal texts to confirm their current wording. Some websites call 6 mg an "EFSA upper limit", but we found no EFSA document that sets one. The only EFSA spermidine opinion we found, from 2011, did not accept a proposed health claim about hair growth[23].

Figure What it is What it is not
6 mg a day Great Britain limit for one wheat germ extract in adult supplements[21] A limit for all spermidine products
3.4 mg a day 2018 authors' safety estimate for a 70 kg adult, from a 28-day mouse study[12] A limit tested in people
Under 40 mg a day POLYCAD team's estimate for adults weighing 50 kg or more, from rat data with a 100-fold margin[24] A regulatory limit

In the US, FDA stopped reviewing the only spermidine GRAS ("generally recognized as safe") notice, for a wheat germ extract, at the company's request in 2020, without a safety decision[25]. In Canada, spermidine is not allowed in natural health products until more safety evidence is provided, according to Health Canada's ingredient database[26].

How do you read the dose on a spermidine label?

Look for milligrams of spermidine per daily serving, not milligrams of extract. Each 750 mg daily serving of wheat germ extract in the trials held only about 0.9 to 1.2 mg of spermidine[2, 12].

  • Extract is not spermidine. SmartAge's six 125 mg capsules held about 0.9 mg of spermidine, plus 0.5 mg of spermine and 0.2 mg of putrescine[2]. The 2018 trial called the same 750 mg dose 1.2 mg of spermidine, and we found no explanation for the gap[12].
  • Per capsule or per serving. Trial servings were 3, 6 or 10 capsules a day[2, 12, 19].
  • Salt or base. For spermidine trihydrochloride (3HCl), check whether the mg figure means the salt or the spermidine[3, 27].
  • Lab-checked content. The 15 mg study had an independent lab confirm the label content[19]. Outside testing is worth looking for.
  • Wheat. Wheat is a major US food allergen, and allergen labelling applies to supplements[28]. In 2025 a spermidine-3HCl product, not a wheat germ extract, was recalled for undeclared wheat[27]. A US "gluten-free" claim means under 20 parts per million of gluten[29].

Our page on spermidine side effects and gluten covers wheat, gluten and reported side effects.

How does food compare with supplement doses?

Typical diets already supply more spermidine than the lowest trial doses[1, 2]. SmartAge's 0.9 mg a day was about 10% of average daily intake, its authors estimated[2].

  • Wheat germ. Commercial wheat germ powders held about 22 to 34 mg per 100 g in one analysis, so 10 g would hold roughly 2.2 to 3.4 mg[10]. It contains wheat, a major allergen[28].
  • Cooking. Raw values can overstate what reaches the plate. Boiling or grilling cut spermidine by as much as about 37% in one Spanish analysis, and finished bread rolls held less than a third of the spermidine in their ingredients[11, 14].

Which higher doses are trials testing now?

Two newer trials use higher doses than most earlier ones. Neither had published results by 8 October 2026[24, 30].

  • POLYCAD (Denmark) gives 24 mg a day or placebo for 48 weeks to 187 adults aged 65 and over with coronary artery disease[24].
  • REPROGRAM (UK) plans to give 15 mg a day for 3 weeks to adults aged 70 and over and measure worn-out (senescent) cells in fat tissue[30].

Why we do not suggest a spermidine dose

We found no trial that compared different spermidine doses against a placebo, and the only year-long placebo-controlled trial found no significant effect on its main outcome[2, 14, 16]. Without better evidence, any "best dose" is a guess.

  • Low doses were deliberate. SmartAge's authors said 0.9 mg may have been too low[2]. They picked that dose partly out of caution, since polyamines promote cell growth and are higher in some tumours[2].
  • Higher doses have short records. As supplements, they were given for only 13 weeks at 6 mg, 5 days at 15 mg and 28 days at 40 mg[3, 17, 19]. The 2026 pilot's authors called 6 mg a conservative starting dose, not an optimised one[17].
  • Autophagy is an open question. One 40-person pilot at 6 mg a day reported more autophagy, the cell's recycling process, in one immune cell type, and its authors called this exploratory[17]. Our page on how spermidine relates to autophagy and fasting explains what is known.

Talk to a clinician first

Trials left out several groups, so they give no safety data for them[2, 12, 17, 24]. Talk to a clinician before taking spermidine if you are pregnant or breastfeeding, which the Great Britain authorisation excludes, or have a wheat or gluten allergy or intolerance, current or past cancer, histamine intolerance or low kidney function, or take blood thinners[2, 12, 17, 21, 24]. Our side effects guide sets out who should check with a clinician first.

For how these numbers fit the wider evidence, see our full review of spermidine research.

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Frequently asked questions

What is the recommended spermidine dosage?

There is no official recommended daily amount of spermidine[1]. Diets supply an estimated 5 to 15 mg a day[1]. Human studies gave about 0.9 to 40 mg a day[2, 3]. Great Britain's 6 mg a day is a cap for one wheat germ extract, not a recommended dose[21]. The only year-long placebo-controlled trial, in 100 older adults with memory complaints, gave about 0.9 mg a day and found no significant effect on its main memory measure[2].

Can you take spermidine every day?

Spermidine trials used daily doses, but only the lowest dose was tested against placebo for a year[2]. SmartAge gave about 0.9 mg a day for 12 months, with side effects similar to placebo[2]. Higher supplement doses were tested only briefly: 6 mg a day for 13 weeks, 15 mg for 5 days and 40 mg for 28 days[3, 17, 19]. Ask a clinician before taking it daily.

Is 10 mg of spermidine a day safe?

We found no published trial of 10 mg of spermidine a day. Nearby doses have short records: 6 mg a day for 13 weeks showed no differences from placebo in blood safety tests, and 15 mg a day was given for only 5 days[17, 19]. Ten milligrams is also above Great Britain's 6 mg cap for one wheat germ extract[21].

How much wheat germ equals a spermidine supplement?

In one lab analysis, commercial wheat germ powders held about 22 to 34 mg of spermidine per 100 g[10]. By that figure, 10 g of wheat germ would supply roughly 2.2 to 3.4 mg[10]. That is more than the 0.9 to 1.2 mg given in the wheat germ extract trials[2, 12]. Wheat germ contains wheat, a major food allergen[28].

Do higher spermidine doses work better?

We found no trial that compared spermidine doses against a placebo, so the evidence cannot show whether more works better[2, 14, 16]. Without a placebo, a 3-month study found blood spermidine rose with 3.3 mg bread rolls but not 1.9 mg rolls, and a 12-person, 8-week pilot reported blood marker changes only at 3.3 mg of rice germ extract, not 1.5 mg[14, 16]. Short trials at 15 and 40 mg a day did not clearly raise blood spermidine[3, 19].

References

  1. Muñoz-Esparza NC, Latorre-Moratalla ML, Comas-Basté O, et al. Polyamines in Food. Front Nutr. 2019. PMID: 31355206
  2. 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 Netw Open. 2022. PMID: 35616942
  3. Keohane P, Everett JR, Pereira R, et al. 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. PMID: 39405978
  4. Zhang X, Qian M, Liu M, et al. The Associations of Dietary Polyamines with Incident Type 2 Diabetes Mellitus: A Large Prospective Cohort Study. Nutrients. 2025. PMID: 39796620
  5. Thorup C, Jensen TH, Jeppesen CNA, et al. Spermidine and spermine in elderly patients with coronary artery disease: a cross-sectional study of dietary intake and plasma and skeletal muscle concentrations. Clin Nutr. 2026. PMID: 42000692
  6. Ali MA, Poortvliet E, Strömberg R, et al. Polyamines: total daily intake in adolescents compared to the intake estimated from the Swedish Nutrition Recommendations Objectified (SNO). Food Nutr Res. 2011. PMID: 21249160
  7. Zoumas-Morse C, Rock CL, Quintana EL, et al. Development of a polyamine database for assessing dietary intake. J Am Diet Assoc. 2007. PMID: 17524725
  8. Toro-Funes N, Comas-Basté O, Latorre-Moratalla M, et al. Dietary Polyamine Intake Across Age Groups in Spain: A Comprehensive Assessment. Nutrients. 2026. PMID: 42197044
  9. Buyukuslu N, Hizli H, Esin K, et al. A Cross-Sectional Study: Nutritional Polyamines in Frequently Consumed Foods of the Turkish Population. Foods. 2014. PMID: 28234336
  10. Mohajeri M, Ayatollahi SA, Kobarfard F, et al. Wheat germ, a byproduct of the wheat milling industry, as a beneficial source of anti-aging polyamines: A quantitative comparison of various forms. Food Sci Nutr. 2023. PMID: 37970387
  11. Muñoz-Esparza NC, Costa-Catala J, Comas-Basté O, et al. Occurrence of Polyamines in Foods and the Influence of Cooking Processes. Foods. 2021. PMID: 34441529
  12. Schwarz C, Stekovic S, Wirth M, et al. Safety and tolerability of spermidine supplementation in mice and older adults with subjective cognitive decline. Aging (Albany NY). 2018. PMID: 29315079
  13. Wirth M, Benson G, Schwarz C, et al. The effect of spermidine on memory performance in older adults at risk for dementia: A randomized controlled trial. Cortex. 2018. PMID: 30388439
  14. Pekar T, Bruckner K, Pauschenwein-Frantsich S, et al. The positive effect of spermidine in older adults suffering from dementia : First results of a 3-month trial. Wien Klin Wochenschr. 2021. PMID: 33211152
  15. Pekar T, Wendzel A, Jarisch R. The positive effect of spermidine in older adults suffering from dementia after 1 year. Wien Klin Wochenschr. 2024. PMID: 37284840
  16. Bruno G, La Monica M, Ziegenfuss TN. 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. PMID: 40862848
  17. Alsaleh G, Ali M, Kayvanjoo AH, et al. Spermidine Mitigates Immune Cell Senescence and Boosts Vaccine Responses in Healthy Older Adults-A Pilot Study. Aging Cell. 2026. PMID: 42169618
  18. Soda K, Uemura T, Sanayama H, et al. Polyamine-Rich Diet Elevates Blood Spermine Levels and Inhibits Pro-Inflammatory Status: An Interventional Study. Med Sci (Basel). 2021. PMID: 33805535
  19. Senekowitsch S, Wietkamp E, Grimm M, et al. 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. PMID: 37111071
  20. Rinaldi F, Marzani B, Pinto D, et al. A spermidine-based nutritional supplement prolongs the anagen phase of hair follicles in humans: a randomized, placebo-controlled, double-blind study. Dermatol Pract Concept. 2017. PMID: 29214104
  21. Food Standards Agency (UK). Spermidine-rich wheat germ extract (Triticum aestivum), NOVEL-130, register of authorised novel foods. Accessed 8 October 2026.
  22. Chrysostomou PP, Freeman EL, Murphy MM, et al. A toxicological assessment of spermidine trihydrochloride produced using an engineered strain of Saccharomyces cerevisiae. Food Chem Toxicol. 2024. PMID: 38163454
  23. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on the substantiation of a health claim related to spermidine and prolongation of the growing phase (anagen) of the hair cycle pursuant to Article 13(5) of Regulation (EC) No 1924/2006. EFSA J. 2011. PMID: 42015976
  24. Thorup CV, Jeppesen CNA, Jensen TH, et al. POLYamine treatment in elderly patients with Coronary Artery Disease (POLYCAD): study protocol for a Danish randomised, double-blind, placebo-controlled trial of spermidine treatment versus placebo. Trials. 2025. PMID: 41168834
  25. US Food and Drug Administration. GRN No. 889: Spermidine rich wheat germ extract, GRAS Notice Inventory. Accessed 8 October 2026.
  26. Health Canada. Chemical Substance - Spermidine, Natural Health Products Ingredients Database. Accessed 8 October 2026.
  27. US Food and Drug Administration (company announcement). Recall of a spermidine supplement, 10 mg capsules (spermidine 3HCl), due to undeclared wheat allergen. April 2025.
  28. US Food and Drug Administration. Food Allergies. Accessed 8 October 2026.
  29. US Food and Drug Administration. Questions and Answers: Gluten-Free Food Labeling Final Rule. Accessed 8 October 2026.
  30. Wilson D, Acharjee A, Duggal NA, et al. REPROGRAM: REsilience PROmotion with GeRoprotectors: AssessMent of biological effect: Rationale and protocol for a trial of biological effect. PLoS One. 2026. PMID: 42308222

This content is for education only and is not medical advice. Talk to your healthcare provider before starting any supplement, especially if you are pregnant, nursing, take medication, or have a medical condition.

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