Comparison
Spermidine vs Urolithin A: Compared on Evidence
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Spermidine and urolithin A both get attention in longevity circles, and people often ask which to try. This page lines up what human trials found for each. For the full evidence and safety, see our spermidine guide and urolithin A guide. For spermidine products see best spermidine supplements. This page has no buy links: we don’t link to urolithin A products, and the spermidine products are on the best spermidine page.
Side by side
| Spermidine A natural compound found in cells and foods; supplements usually use wheat germ extract | Urolithin A A compound made by gut bacteria from plant chemicals; supplements use a lab-made form | |
|---|---|---|
| What it is | A natural compound in your cells and in many foods. In lab and animal studies it switches on a cell clean-up process called autophagy. | A compound your gut bacteria make from chemicals in foods such as pomegranates, berries and walnuts. In animals it helped muscle function. |
| Evidence grade (our scale) | D: interesting, but early. | D: early and promising, but not proven. |
| Main human trial | 100 adults aged 60 to 90 with memory worries, 12 months at 0.9 mg a day. | Several small trials of 4 weeks to 4 months at 500 or 1,000 mg a day, in older and middle-aged adults. |
| What trials measured and found | Memory test: no significant change in the main measure. Possible gains in verbal memory and inflammation were exploratory. Scans of brain blood flow were exploratory too. | Muscle endurance and strength: some measures improved, but main goals were missed in two trials. Mitochondrial and immune markers shifted. Artery function did not change in a 50-person trial in adults with obesity. |
| Who funded the research | Several authors of the main trial have links to a spermidine company. | Several trials were funded by the maker of the main product. See our urolithin A guide for each. |
| Amounts used in trials | 0.9 to 1.2 mg of spermidine a day in the memory trials. These are study amounts, not recommendations. | 500 mg or 1,000 mg a day. These are study amounts, not recommendations. |
| Typical cost (our product data) | From $0.62 to $1.25 (US) or £2.47 (UK) per daily serving on the label, checked Nov 3, 2026. Amounts per serving range from 2 mg to 21 mg of spermidine. | Not shown: we don't link to urolithin A products. |
| Who might prefer it | We found no evidence on who should choose each, so we make no claim. | Same: we found no evidence either way. |
Our verdict
We can't say which is better, because no trial has compared them. They are different compounds studied for different things: spermidine mostly in memory trials, urolithin A mostly in muscle and immune trials. The best spermidine memory trial missed its main goal, and the urolithin A trials often missed theirs too, so both stay at grade D.
What spermidine trials show
In 100 older adults with subjective cognitive decline (memory worries), 12 months of spermidine did not significantly change the main memory test. The authors reported possible gains in verbal memory and inflammation as exploratory findings that need confirming, and several authors have links to a spermidine company. Source: Schwarz C et al., JAMA Netw Open, 2022 (PubMed · DOI). An exploratory MRI analysis of 75 of these people found regional differences in brain blood flow and a white matter measure, but they were not linked to memory changes and the authors call them preliminary. Source: Schwarz C et al., Aging Dis, 2026 (PubMed · DOI). An earlier safety study in older adults with memory worries found it was well tolerated. Source: Schwarz C et al., Aging (Albany NY), 2018 (PubMed · DOI).
What urolithin A trials show
In 66 adults aged 65 to 90, 1,000 mg a day for 4 months improved muscle endurance at 2 months, but the main goals (walking distance and muscle energy production) showed no significant difference from placebo. Source: Liu S et al., JAMA Netw Open, 2022 (PubMed · DOI). In middle-aged adults, muscle strength rose about 12% in a company-funded trial, but the main goal (peak power output) did not improve significantly. Source: Singh A et al., Cell Rep Med, 2022 (PubMed · DOI). In 50 healthy middle-aged adults, 4 weeks changed the make-up and activity of some immune cells; the maker funded it. Source: Denk D et al., Nat Aging, 2025 (PubMed · DOI). In 50 adults with obesity, 4 weeks did not significantly change artery widening, the main measure. Source: da Costa Pinaffi-Langley AC et al., JAMA Netw Open, 2026 (PubMed · DOI). A 2026 review found five small, short trials (236 people) and called the findings hypothesis-generating. Source: Dao T et al., Front Nutr, 2026 (PubMed · DOI).
Why we can’t pick a winner
The trials measured different things in different people for different lengths of time, so their results can’t be lined up. Several were funded by the makers of the products tested. Both compounds have mostly early evidence, so what you spend should match how much that matters to you.
Talk to your doctor or pharmacist
Talk to your doctor or pharmacist before you start any supplement, especially if you are pregnant or breastfeeding, take prescription medicine, or have a health condition. Spermidine supplements often come from wheat germ, so check the label if you have a wheat allergy or celiac disease.
FAQ
Spermidine vs urolithin A: which is better?
No one can say. We found no trial comparing them. They were studied for different outcomes, and the best spermidine memory trial and several urolithin A trials missed their main goals.
Can you take spermidine and urolithin A together?
We found no trial testing the pairing, so we can’t say whether it adds anything. Ask a doctor or pharmacist about your own situation.
Which has more human evidence?
Urolithin A has more small human trials, mostly 4 weeks to 4 months, while the best spermidine supplement trial lasted 12 months. Both are grade D on our scale, meaning early evidence.