Sunlit wheat field at golden hour with a calm winding path leading toward a bright open doorway
October 09, 2026

Spermidine Side Effects and Safety

By SciRouter Editorial Team · Last reviewed: 9 October 2026

Spermidine supplements were well tolerated in the small human trials published so far. Adverse events were similar with spermidine and placebo, and routine blood tests did not differ[1–4]. One 12-month trial recorded more joint and muscle complaints with spermidine[1]. The main cautions are wheat and gluten in wheat-germ products, missing data in pregnancy, and a history of cancer[2, 5, 6].

This page is the safety companion to our spermidine supplement evidence guide. For the amounts used in studies, see our guide to daily spermidine doses in trials.

Important: If you have celiac disease, a wheat allergy, or a current or past cancer diagnosis, talk to your doctor or oncologist before taking spermidine.

How we researched this. We searched PubMed through NCBI E-utilities, read Europe PMC full text where it was open, and checked agency pages from the UK Food Standards Agency, the US FDA and Health Canada. Searches ran on 8 October 2026. We put human trials first, then observational studies, and labelled animal studies by species. We cited only sources we opened and checked against PubMed or the agency's own site. This page cites 24 sources. We sell no spermidine product. This page is not medical advice.

What spermidine side effects did trials report?

In placebo-controlled trials of up to 12 months, adverse events were similar with spermidine and placebo[1–4]. The one imbalance was more muscle, bone or joint complaints with spermidine in the SmartAge trial[1].

An adverse event is any health problem recorded during a trial, whether or not the supplement caused it. In these trials, no serious adverse event was judged likely to be caused by spermidine[1–4].

Study People Daily dose and length Adverse events as reported
SmartAge trial, 2022[1] 100 adults aged 60–90 with memory complaints About 0.9 mg from wheat germ extract, 12 months 58 adverse events vs 71 on placebo. Serious events 7 vs 12, none judged related. Muscle, bone or joint problems in 11 vs 4 people
Safety trial, 2018[2] 30 adults aged 60–80 with memory complaints 1.2 mg from wheat germ extract, 3 months No differences from placebo in vital signs, weight, blood chemistry or blood counts. One serious event per group, neither judged likely related
UK pilot trial, 2026[3] 40 adults over 65 6 mg from wheat germ extract, 13 weeks Well tolerated; no supplement-related adverse events; blood safety tests, compared at week 2, did not differ
Higher-dose trial, 2024[4] 37 healthy men aged 50–70 40 mg of a purified spermidine salt, 28 days No significant changes in routine blood tests; no product-related adverse events
Blood-level study, 2023[7] 12 healthy adults 15 mg, 5 days Adverse events not reported
Radiotherapy trial, 2026[8] 58 adults having head and neck radiotherapy 1 mg, from 1 week before to 1 week after radiotherapy No severe adverse events; mild bloating or diarrhea in a few people in both groups
Rice germ pilot, 2025[9] 12 adults, no placebo group 1.5 or 3.3 mg, 8 weeks Authors reported a good safety profile for the 3.3 mg dose
  • The muscle and joint imbalance. Most of these complaints were age-related conditions such as osteoporosis, arthritis, gout attacks and joint pain[1].
  • Small, short and mostly older adults. The seven studies enrolled under 300 people, and the longest lasted 12 months[1–4, 7–9]. Four enrolled only people aged 50 or older[1–4].
  • Industry links. One supplement company supplied the extract for three trials, and some authors held equity in it or consulted for it[1–3]. Two authors of the 40 mg trial, including the lead author, worked for the ingredient's maker[4].

Is spermidine safe at higher doses?

Higher doses have little safety data: we found only two published supplement trials above 6 mg a day[4, 7]. At 40 mg a day for 28 days, 37 men had no significant routine blood-test changes and no product-related adverse events[4].

The other study gave 15 mg a day to 12 healthy adults for 5 days and did not report on adverse events[7]. Both were too small and short to detect rare or long-term effects[4, 7].

Animal studies give a rough sense of the margin:

  • Rats, 6 weeks. The highest intake with no observed harm was 83 mg per kg of body weight a day. At the top doses, blood creatinine, calcium and phosphate fell[10].
  • Rats, 90 days. In a study funded by an ingredient maker, spermidine trihydrochloride produced no reported adverse effects up to the highest dose tested, 728 mg per kg a day in males[11].
  • Mice, 28 days. The only organ change was a 12% higher relative kidney weight in female mice given an extreme overdose of wheat germ extract[2].

Two research teams have turned these animal results into human estimates, but the estimates differ widely and are not tested or legal limits[2, 12]. Our spermidine dosage guide compares those estimates with trial doses, food intake and the higher-dose trials now under way.

What have regulators said about spermidine safety?

No regulator we found has set a safe upper intake level for spermidine[5, 13, 14]. Great Britain allows one wheat germ extract in adult supplements at up to 6 mg of spermidine a day[5].

Health Canada says spermidine cannot be used in natural health products without more safety evidence[13]. The table sets out what each agency has said, plus one recall posted by the FDA.

Body What it covers What it says
UK Food Standards Agency, Great Britain[5] Spermidine-rich wheat germ extract Allowed in food supplements for adults, excluding pregnant and breastfeeding women, up to the equivalent of 6 mg spermidine a day
Health Canada[13] Spermidine in natural health products Not allowed without more evidence of safety (record dated 2019)
US FDA, GRAS notice inventory[14] One notice for a spermidine-rich wheat germ extract in foods Evaluation stopped in 2020 at the company's request, with no safety decision
Company recall posted by the FDA, 2025[15] One supplement sold as spermidine trihydrochloride Recalled because it contained wheat not declared on the label

GRAS means "generally recognized as safe", a US status for food ingredients. In the UK register, 6 mg is a usage condition attached to one adult-supplement ingredient. It is not a safe upper limit for spermidine from all sources[5]. We could not verify any EFSA (European Food Safety Authority) safety opinion or upper limit for this ingredient, so we do not cite one.

Spermidine and gluten: what to check

Great Britain's authorised spermidine ingredient is a wheat germ extract, and wheat is a gluten-containing grain[5, 16]. If you have celiac (coeliac) disease, a wheat allergy or gluten sensitivity, check the label and ask the maker for gluten test results.

  • In celiac disease, eating gluten damages the lining of the small intestine, according to the FDA[16].
  • Wheat is a major food allergen in the US, and allergen labelling rules apply to dietary supplements[17].
  • Two wheat germ trials excluded people with wheat germ or gluten allergy or gluten intolerance, so they offer no safety data for these groups[2, 3].
  • We found no verified, published measurement of gluten in spermidine-rich wheat germ extracts.
  • Other forms are not automatically wheat-free. In 2025, a supplement sold as spermidine trihydrochloride was recalled for undeclared wheat. The company warned that people with a wheat allergy or severe sensitivity risked a serious or life-threatening allergic reaction, though none had been reported[15].

What to check on the label:

  • The source. Trials used wheat germ, rice germ, a chlorella and soybean product, and a purified salt[1, 4, 7, 9].
  • Wheat declared as an allergen. US labelling rules require it[17].
  • A "gluten-free" claim. The claim is voluntary. If a supplement makes it, any unavoidable gluten must be below 20 parts per million (ppm)[16].
  • Wheat plus "gluten-free". A label that lists wheat and claims to be gluten-free must also state that the wheat was processed to meet FDA gluten-free rules[16].
  • A test result. Ask the maker for a recent certificate of analysis that reports gluten in ppm.

Pregnancy, breastfeeding and children: no safety data

We found no published safety data for spermidine supplements in pregnancy, breastfeeding or childhood. Great Britain's authorisation covers adults only and excludes pregnant and breastfeeding women[5].

None of the trials above was designed to study these groups[1–4, 7–9]. Spermidine is also part of everyday food, especially plant foods[18]; see which foods contain the most spermidine. If you are pregnant, breastfeeding or choosing for a child, ask a doctor or midwife first.

Spermidine and cancer: why researchers urge caution

Spermidine belongs to the polyamines, which cells need to grow, and polyamine metabolism is often disrupted in tumours[6, 19]. If you have a current or past cancer diagnosis, speak with your oncologist before taking spermidine.

This caution rests on biology, not on evidence of harm from supplements. The trials were small and short, and SmartAge and the 2018 trial excluded people who had had cancer, so they cannot settle the question[1, 2].

  • The SmartAge team chose a low dose partly because polyamine levels are higher in some tumours and polyamines promote cell growth[1].
  • Authors of a 2024 study on fasting and spermidine noted that polyamine levels are raised in many cancer types and may spur cell growth, so the effects of fasting in people with cancer need careful evaluation[20]. Our page on spermidine, autophagy and fasting explains what that study found.

Observational studies of diet show links, not cause and effect, and their results are mixed[21–24]:

Study People What was found
Diet and colorectal polyps, 2012[21] 1,164 adults with past colorectal polyps Above-median polyamine intake from food was associated with 39% higher odds of new polyps
Women's Health Initiative, 2015[22] 87,602 postmenopausal women Polyamine intake from food was not associated with higher colorectal cancer risk
US screening-trial cohort, 2026[23] 54,517 men Spermidine intake from food was not associated with prostate cancer or prostate cancer death
Takayama study, Japan, 2024[24] About 29,000 adults followed for 16 years No significant link with overall or cause-specific death; a borderline signal for cancer death in women with the highest vs lowest spermidine intake (hazard ratio 1.38, 95% CI 0.99 to 1.93)

A hazard ratio of 1.38 means a 38% higher rate. The 95% confidence interval, the range the data fit, just included 1.0 (no difference), so that comparison was not statistically significant. The trend across the four intake groups was significant (P = 0.02), and the authors called the link suggestive[24]. All four studies measured food, not supplements[21–24].

Does spermidine interact with medications?

We found no published study designed to test spermidine supplements for interactions with any medicine. Interaction risks are therefore unknown, not ruled out.

The 2018 safety trial excluded people taking anticoagulants or platelet inhibitors, two kinds of blood thinner, and people with histamine intolerance[2]. If you take a prescription medicine, ask your pharmacist or prescriber first. Don't stop or change a prescribed medication without talking to your prescriber.

Who should talk to a clinician first?

Talk to a doctor or pharmacist before taking spermidine if any point below applies to you. Most describe groups that trials or regulators left out, so there is no evidence either way[2, 3, 5, 12].

  • Celiac disease, wheat allergy or gluten sensitivity. Two trials excluded people with wheat germ or gluten allergy or gluten intolerance[2, 3].
  • A current or past cancer diagnosis. Speak with your oncologist first[1, 2, 6].
  • Pregnancy, breastfeeding or under 18. Great Britain's authorisation covers adults only and excludes pregnant and breastfeeding women[5].
  • Taking blood thinners, or histamine intolerance. The 2018 trial excluded both groups[2].
  • Reduced kidney function. A Danish spermidine trial in older adults with coronary artery disease (POLYCAD) excludes people with an eGFR below 45, a blood-test estimate of how well the kidneys filter[12].
  • Any regular prescription medicine. We found no interaction studies.
  • Plans for high doses or long-term use. Trials tested about 0.9 mg a day for 12 months, 6 mg for 13 weeks and 40 mg for 28 days[1, 3, 4].

For what spermidine has and has not been shown to do, read our yeast-to-humans review of the spermidine evidence.

Get our plain-English longevity research digest

Short, sourced summaries of new longevity research, written in plain English. No product pitches. Unsubscribe anytime.

Frequently asked questions

Is spermidine safe?

In small trials lasting up to 12 months, spermidine supplements were well tolerated, and adverse events were similar to placebo[1–4]. Doses ran from about 0.9 to 6 mg a day, plus 40 mg a day for 28 days[1, 3, 4]. The 2018 safety trial excluded people with past cancer, wheat or gluten allergy, or blood-thinner use, so safety in those groups is unknown[2].

What are the side effects of taking spermidine?

No serious adverse event in the spermidine trials was judged likely to be caused by spermidine[1–4]. In the 12-month SmartAge trial, 11 people taking spermidine and 4 taking placebo reported muscle, bone or joint problems, mostly age-related[1]. In a 58-patient trial, a few people in both groups had mild bloating or diarrhea[8]. Rare side effects could still be missed.

Does spermidine contain gluten?

Spermidine supplements can contain gluten, depending on the source. The ingredient authorised in Great Britain is a wheat germ extract, and wheat is a gluten-containing grain[5, 16]. Other forms can carry wheat too: a spermidine trihydrochloride supplement was recalled in 2025 because its label did not declare wheat[15]. In the US, a "gluten-free" label means under 20 ppm gluten[16]. People with celiac disease or a wheat allergy should check first.

What not to take with spermidine?

There is no tested list, because we found no published study designed to test spermidine for interactions with any medicine. The 2018 safety trial excluded people taking anticoagulants or platelet inhibitors, so there are no data for people on blood thinners[2]. If you take any prescription medicine, ask your pharmacist or prescriber before starting spermidine.

Is spermidine hard on the liver?

Small trials found no sign that spermidine harms the liver, but the evidence is thin. Routine blood chemistry, including liver tests, did not differ from placebo with 1.2 mg a day for 3 months, or with 6 mg a day when checked at week 2[2, 3]. A 40 mg trial lasting 28 days found no significant blood chemistry changes[4]. None was designed to study the liver. If you have a liver condition, ask your doctor first.

Can spermidine cause cancer?

Spermidine trials were not designed to answer this, and the two main wheat germ trials excluded people with past cancer[1, 2]. Polyamines such as spermidine are needed for cell growth and are often raised in tumours, one reason SmartAge used a low dose[1, 6]. Food studies are mixed: higher intake was linked to more new colorectal polyps in people with past polyps, but not to colorectal or prostate cancer in large cohorts[21–23]. Ask your oncologist first.

References

  1. 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
  2. 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
  3. 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
  4. 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
  5. Food Standards Agency (UK). Spermidine-rich wheat germ extract (Triticum aestivum) - NOVEL-130. Register of authorised novel foods. Last updated 1 April 2025.
  6. Casero RA Jr, Murray Stewart T, Pegg AE. Polyamine metabolism and cancer: treatments, challenges and opportunities. Nat Rev Cancer. 2018. PMID: 30181570
  7. 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
  8. Min Y, Gao K, Liu Y, et al. Oral Spermidine Supplementation Preserves Submandibular Gland Function After Radiotherapy: Mechanistic Insights and Use in a Phase II Randomized Clinical Trial. MedComm (2020). 2026. PMID: 42460130
  9. 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
  10. Til HP, Falke HE, Prinsen MK, et al. Acute and subacute toxicity of tyramine, spermidine, spermine, putrescine and cadaverine in rats. Food Chem Toxicol. 1997. PMID: 9207896
  11. 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
  12. 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
  13. Health Canada. Chemical Substance - Spermidine (Natural Health Products Ingredients Database). Record last modified 1 March 2019.
  14. US Food and Drug Administration. GRN No. 889 Spermidine rich wheat germ extract (GRAS Notice Inventory). Closed 20 March 2020.
  15. US Food and Drug Administration (company announcement). Recall of a spermidine 3HCl supplement due to undeclared wheat allergen. 14 April 2025.
  16. US Food and Drug Administration. Questions and Answers: Gluten-Free Food Labeling Final Rule. Accessed 8 October 2026.
  17. US Food and Drug Administration. Food Allergies. Accessed 8 October 2026.
  18. Muñoz-Esparza NC, Latorre-Moratalla ML, Comas-Basté O, et al. Polyamines in Food. Front Nutr. 2019. PMID: 31355206
  19. Gerner EW, Meyskens FL Jr. Polyamines and cancer: old molecules, new understanding. Nat Rev Cancer. 2004. PMID: 15510159
  20. Hofer SJ, Daskalaki I, Bergmann M, et al. Spermidine is essential for fasting-mediated autophagy and longevity. Nat Cell Biol. 2024. PMID: 39117797
  21. Vargas AJ, Wertheim BC, Gerner EW, et al. Dietary polyamine intake and risk of colorectal adenomatous polyps. Am J Clin Nutr. 2012. PMID: 22648715
  22. Vargas AJ, Ashbeck EL, Wertheim BC, et al. Dietary polyamine intake and colorectal cancer risk in postmenopausal women. Am J Clin Nutr. 2015. PMID: 26135350
  23. Wang G, Lin J, Lin Z, et al. Dietary spermidine intake is not associated with prostate cancer incidence or prostate cancer-specific mortality: findings from the prostate, lung, colorectal, and ovarian cancer screening trial. Front Nutr. 2026. PMID: 42591195
  24. Nagata C, Wada K, Yamakawa M, et al. Dietary polyamine intake and all-cause and cause-specific mortality in Japanese adults in the Takayama study. Br J Nutr. 2024. PMID: 37964604

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.

more Blog posts

View all