Two supplements dominate conversations about cellular longevity right now: urolithin A and nicotinamide mononucleotide (NMN). Both are backed by genuine research and both work at the level of the mitochondria — the energy-producing structures inside cells. But they arrive there by entirely different routes, and understanding that distinction matters if you are trying to make a thoughtful decision.
This article walks through what each compound does, what human clinical trials have actually shown, and where the evidence is still developing. Neither supplement is a cure for aging, and neither has been tested head-to-head in a clinical trial. What exists is a growing body of human data on each, taken separately, that is worth examining honestly.
Key Takeaways
- Urolithin A activates mitophagy — a cellular cleanup process that removes damaged mitochondria — while NMN replenishes NAD+, a coenzyme essential for energy metabolism and DNA repair.
- Human randomized trials have shown urolithin A improves muscle endurance and strength in middle-aged and older adults, with measurable mitochondrial gene expression changes [4] [6].
- NMN reliably raises blood NAD+ levels in humans and has shown metabolic benefits such as improved insulin sensitivity in specific populations [8] [2], but functional performance data is less established.
- The two compounds work through different and potentially complementary pathways; no human trial has tested them in combination.
- Both supplements have short-term safety data in humans, but neither has been studied for long-term use at scale, and neither replaces exercise, sleep, or a healthy diet.
How Urolithin A Works: Clearing Out Damaged Mitochondria
Urolithin A is a postbiotic compound — it is produced in the gut when certain gut bacteria metabolize polyphenols found in foods like pomegranate, berries, and walnuts. The molecule itself is not found in food in meaningful amounts; your gut flora make it. Critically, many people lack the gut bacteria needed to produce urolithin A in significant quantities, which is why oral supplementation has become a research focus.
Its primary mechanism is the activation of mitophagy — a cellular quality-control process that selectively removes damaged or dysfunctional mitochondria so healthy ones can replace them. As cells age, dysfunctional mitochondria accumulate and impair energy production. By stimulating mitophagy, urolithin A helps cells clear that backlog. A comprehensive review of the compound described this mitophagy-activation pathway as central to its effects on muscle function, inflammation, and longevity-related biology [3].
A first-in-human safety trial found that oral urolithin A supplementation was well tolerated and produced a molecular signature consistent with improved mitochondrial and cellular health — including changes in gene expression related to mitochondrial biogenesis and autophagy — measurable in muscle tissue [1].
How NMN Works: Replenishing a Critical Coenzyme
NMN — nicotinamide mononucleotide — works through a fundamentally different pathway. It is a precursor to NAD+ (nicotinamide adenine dinucleotide), a coenzyme essential for hundreds of metabolic reactions including cellular energy production, DNA repair, and the activity of sirtuins, a family of proteins implicated in longevity regulation. NAD+ levels decline with age, and restoring them is the central rationale for NMN supplementation.
Unlike urolithin A, NMN does not primarily activate waste-clearance pathways. Instead it aims to restore the raw metabolic fuel that mitochondria and repair enzymes need to function properly. A 2025 review summarized the biological properties and anti-aging mechanisms attributed to NMN, noting that its conversion to NAD+ in tissues underpins most of its proposed effects, though human evidence is still accumulating [12]. Researchers have also noted that the rate at which NMN is absorbed and converted to NAD+ in different tissues remains an active area of investigation [5].
What Human Trials Show for Urolithin A
Urolithin A has now been tested in several randomized controlled trials in humans. In a 2022 trial in middle-aged adults, supplementation improved muscle strength and exercise performance alongside biomarkers of mitochondrial health compared to placebo [6]. A separate randomized clinical trial published the same year, focused on older adults, found improvements in muscle endurance — specifically in how long participants could perform a hand-grip fatigue test — along with favorable changes in mitochondrial gene expression [4].
Beyond muscle, a 2022 study found that urolithin A reduced markers of cartilage degeneration and pain in an osteoarthritis model, suggesting the mitophagy mechanism may have relevance for joint tissues as well [7]. A 2024 systematic review synthesizing human studies concluded that evidence supports urolithin A as a promising agent for targeting aspects of aging, particularly around muscle and mitochondrial health, while calling for larger and longer trials [10].
What Human Trials Show for NMN
NMN research in humans has expanded considerably in recent years. A double-blind, placebo-controlled, dose-dependent trial in healthy middle-aged adults found that NMN supplementation raised blood NAD+ levels and was well tolerated across a range of doses, with higher doses producing larger NAD+ increases [8]. A 2023 review of human clinical trials concluded that NMN appears safe in the short-term doses tested and produced some favorable physiological markers, though the authors noted that most trials are still small and of short duration [9].
One notable human finding came from a study in prediabetic women, in which NMN supplementation improved skeletal muscle insulin sensitivity — a meaningful metabolic outcome — over a 10-week period [2]. That said, whether these metabolic effects translate into durable functional benefits for healthy individuals remains an open question. A 2024 review of NMN’s anti-aging effects in humans called for standardized outcome measures and longer follow-up periods before firm conclusions can be drawn [11].
Comparing the Two: Different Targets, Different Evidence Bases
The core difference is mechanistic. Urolithin A activates a cleanup process — mitophagy — that removes cellular debris. NMN replenishes a metabolic coenzyme — NAD+ — that supports energy production and repair. These are complementary rather than competing actions, which is why some researchers speculate they could work synergistically, though no human trial has tested that combination.
In terms of human evidence, urolithin A has produced measurable functional outcomes (grip strength, muscle endurance) in randomized trials, with direct measurement of mitochondrial gene expression changes in muscle biopsies providing mechanistic support [1] [4]. NMN’s strongest human evidence to date involves reliably raising NAD+ levels in the blood [8] and improving insulin sensitivity in a specific population [2], but translation into functional endpoints like muscle performance or exercise capacity in healthy adults is less established.
It is also worth noting that urolithin A production from diet is highly variable — studies suggest a large proportion of adults are non-producers, making supplementation the only reliable way to obtain meaningful levels [3]. NMN, by contrast, is present in small amounts in certain foods, though dietary amounts are far below those used in trials.
Practical Considerations: Who Might Consider Each
Neither supplement is appropriate as a substitute for foundational health practices — exercise, sleep, and nutrition drive mitochondrial health more robustly than any supplement studied to date. Within that context, urolithin A has the most specific human evidence in populations concerned about muscle function, exercise capacity, and mitochondrial decline — particularly middle-aged and older adults [6] [4]. Its safety profile has been characterized in clinical trials, with no serious adverse events reported in published studies [1].
NMN may appeal to those focused on metabolic health, given its insulin-sensitivity finding [2], or to those interested in the broader NAD+ biology literature. The safety signal in human trials is generally reassuring for short-term use [9], though long-term safety data is limited for both compounds. Anyone on medications, with chronic illness, or pregnant should consult a physician before adding either supplement.
🛒 Where to Buy Urolithin A
- Timeline Mitopure SoftgelsClinically studied
softgels, 500 mg/day — The clinically studied form (Amazentis); used in the human trials. - DoNotAge Pure Urolithin A
capsules, 250-500 mg — Popular longevity-brand generic, third-party tested. - ProHealth Longevity Urolithin A
capsules, 500 mg — Longevity-focused brand, often higher dose. - Double Wood Urolithin A
capsules, 250-500 mg — Budget-friendly, widely available, COA on request.
As an Amazon Associate we earn from qualifying purchases. Prices and availability vary; verify dose and third-party testing before buying.
A Note on the Evidence
The human evidence base for both urolithin A and NMN is still developing — most trials are small, short in duration, and conducted in specific populations, so results may not generalize to everyone. Neither supplement has been approved to treat, cure, or prevent any disease, and neither should replace medical care or established healthy behaviors. People who are pregnant, have chronic illnesses, or take prescription medications should consult a physician before using either supplement.
Frequently Asked Questions
Can urolithin A and NMN be taken together?
No human trial has tested them in combination, so there is no direct evidence on whether co-supplementation is more effective or raises any safety concerns. Mechanistically they target different pathways — mitophagy and NAD+ replenishment — which are not known to interfere with each other. Consult a healthcare provider before stacking supplements.
Has urolithin A been tested in human clinical trials?
Yes. A first-in-human trial confirmed safety and showed mitochondrial health biomarker improvements in muscle tissue [1]. Subsequent randomized trials found improvements in muscle endurance in older adults [4] and muscle strength and exercise performance in middle-aged adults [6].
Does NMN actually raise NAD+ levels in humans?
Yes. A dose-dependent randomized trial in healthy middle-aged adults demonstrated that NMN supplementation increased blood NAD+ levels, with higher doses producing larger increases, and the supplement was well tolerated [8]. Whether raising blood NAD+ translates into tissue-level benefits in healthy people remains under investigation.
Why can't people just eat pomegranate instead of supplementing urolithin A?
Because urolithin A is not in pomegranate — gut bacteria produce it from pomegranate polyphenols. Research indicates that a large fraction of adults lack the gut microbiome composition needed to produce urolithin A in meaningful amounts, regardless of diet [3]. Supplementation bypasses this conversion step.
What is mitophagy and why does it matter for aging?
Mitophagy is a selective form of autophagy — the cell’s internal recycling system — that specifically targets damaged or dysfunctional mitochondria for breakdown and removal. As cells age, dysfunctional mitochondria accumulate, impairing energy production and promoting inflammation. Activating mitophagy helps restore the quality of the mitochondrial pool. Urolithin A is described as a mitophagy activator in both preclinical and human research [3] [1].
Is NMN safe, and are there any known concerns?
Short-term human trials have generally found NMN to be well tolerated [9]. However, a review of NMN as a health product noted that long-term safety data in humans is limited, and questions remain about optimal dosing, potential effects on cell proliferation over time, and interactions with certain medications [5]. People with existing health conditions should speak with a doctor before use.
References
- Andreux PA et al. The mitophagy activator urolithin A is safe and induces a molecular signature of improved mitochondrial and cellular health in humans. Nature metabolism (2019). PMID 32694802
- Yoshino M et al. Nicotinamide mononucleotide increases muscle insulin sensitivity in prediabetic women. Science (New York, N.Y.) (2021). PMID 33888596
- D'Amico D et al. Impact of the Natural Compound Urolithin A on Health, Disease, and Aging. Trends in molecular medicine (2021). PMID 34030963
- Liu S et al. Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults: A Randomized Clinical Trial. JAMA network open (2022). PMID 35050355
- Nadeeshani H et al. Nicotinamide mononucleotide (NMN) as an anti-aging health product – Promises and safety concerns. Journal of advanced research (2022). PMID 35499054
- Singh A et al. Urolithin A improves muscle strength, exercise performance, and biomarkers of mitochondrial health in a randomized trial in middle-aged adults. Cell reports. Medicine (2022). PMID 35584623
- D'Amico D et al. Urolithin A improves mitochondrial health, reduces cartilage degeneration, and alleviates pain in osteoarthritis. Aging cell (2022). PMID 35778837
- Yi L 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). PMID 36482258
- Song Q et al. The Safety and Antiaging Effects of Nicotinamide Mononucleotide in Human Clinical Trials: an Update. Advances in nutrition (Bethesda, Md.) (2023). PMID 37619764
- Kuerec AH et al. Targeting aging with urolithin A in humans: A systematic review. Ageing research reviews (2024). PMID 39002645
- Han M et al. [Research progress on anti-aging effects of β-nicotinamide mononucleotide (NMN)]. Sheng li xue bao : [Acta physiologica Sinica] (2024). PMID 39780578
- Wang E et al. Biological properties, synthetic pathways and anti-aging mechanisms of nicotinamide mononucleotide (NMN): Research progress and challenges. Biogerontology (2025). PMID 40550930
