Comparison
Urolithin A vs. Spermidine
Urolithin A or spermidine – which longevity compound is better proven in humans?
The short answer
Both compounds target the cell's self-renewal, but the evidence sits in different places. Urolithin A has the denser chain in humans: in muscle biopsies it changed the expression of mitochondrial genes, and two randomised trials over 4 months found better muscle endurance and about 12 percent more leg strength respectively. Spermidine has the stronger epidemiology – in the Bruneck cohort and the UK Biobank, higher dietary intake went along with lower mortality – and a mechanism causally tested in animal models. Where the data end: both urolithin A trials missed their primary outcome and were funded by the manufacturer, and SmartAge on spermidine missed its primary memory endpoint. Hard endpoints in humans are missing for both, and there is no direct comparison.
The numbers side by side
| Axis | Urolithin A | Spermidine | Difference |
|---|---|---|---|
| Human evidenceHow much and how good the data in humans are | 5 | 5 | even |
| MechanismHow well the chain of action is understood | 7 | 6 | Urolithin A better studied |
| Safety dataHow well safety has been studied – not how safe it is | 7 | 6 | Urolithin A better studied |
| Hype gap10 means: the advertising stays level with the data | 4 | 3 | Urolithin A closer to the data |
| Track record of useHow much documented use in humans exists – does not measure whether it works | 4 | 6 | Spermidine in use longer |
| Rating | Thin human evidence · Thin human evidence | ||
“Track record of use” measures how long and how widely something has been used in humans – not whether it works. The BK-Score is a subjective assessment by Biohacking Kompakt based on published scoring rules (German). It is not a scientific rating, not the consensus of a professional society and not a medical recommendation.
Why these numbers
Urolithin A
The mitophagy chain of action is supported in humans by biomarkers: in the first human study (Nature Metabolism 2019), urolithin A changed mitochondrial gene expression in muscle after 4 weeks. Two randomised, placebo-controlled trials over 4 months – 66 people aged 65 to 90 (JAMA Network Open 2022) and 88 middle-aged adults (Cell Reports Medicine 2022) – showed better muscle endurance and about 12% more leg strength respectively, as well as lower CRP, but both missed their primary outcome; both were funded by the manufacturer Amazentis. In trained runners, performance did not improve. After pomegranate juice, only about 40% of people produced meaningful amounts of urolithin A – something rarely mentioned in advertising.
Spermidine
Several randomised, double-blind trials exist, including SmartAge with 100 participants over 12 months – whose primary memory endpoint was missed. The other human studies are small, short and measure surrogate markers; autophagy has been measured in humans once, in B cells in a pilot study with 40 participants. The mechanism has been causally tested in animal models, and the cohort data on mortality are robust and replicated. Pharmacokinetically, even 15 and 40 mg daily do not raise the spermidine level in the blood. Wheat germ extract has been authorised in the EU as a novel food since 2017/2018, maximum 6 mg per day; health claims are not authorised. It is nevertheless marketed as a fasting substitute you can swallow.
Frequently asked questions
Is urolithin A better than spermidine?
There is no direct comparison; one can only put the studies side by side. Urolithin A has the chain of action tested closer to humans: mitochondrial genes in muscle and two randomised muscle trials over 4 months. Spermidine has the stronger observational data and a mechanism causally tested in animals, but only a single autophagy measurement in humans. In the BK-Score, both carry the label “Thin human evidence” with human evidence 5.
What do urolithin A and spermidine do in the cell?
Both target the cell's self-cleaning, but at different points. Urolithin A is meant to stimulate mitophagy, the recycling of worn-out mitochondria; in humans it changed the expression of mitochondrial genes in muscle after 4 weeks. Spermidine is meant to switch on autophagy, by which cells break down damaged components. In humans this has been measured once so far: in a pilot study with 40 participants, increased only in B cells, not in T cells.
Can you get urolithin A and spermidine from food?
Urolithin A only indirectly: gut bacteria make it from tannins in pomegranate, walnuts and berries, but after pomegranate juice only about 40 percent of people produced meaningful amounts. Spermidine is found directly in food, most of all in wheat germ, as well as in mushrooms, green peppers, peas, citrus fruits and tempeh. Cooking and grilling reduce the content by up to 64 percent. The cohort data on mortality refer to spermidine from food, not from capsules.
How safe are urolithin A and spermidine?
Both were well tolerated in controlled studies. On urolithin A, no more side effects occurred than on placebo over up to 4 months; for spermidine, adverse events in SmartAge were balanced over 12 months. Longer-term data are missing for both. For spermidine, the German consumer advice centre advises people with cancer or on immunosuppressants to consult a doctor first. There are no data on urolithin A for pregnant and breastfeeding women, and the EU authorisation for spermidine excludes them.
See all ratings in the ranking (German app)
Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in a doctor's hands.