Urolithin A vs HMB
Urolithin A and HMB are both muscle-minded supplements, but they aim at different parts of the same problem. Urolithin A works inside muscle cells to support the renewal of mitochondria, the structures that power contraction. HMB is a leucine metabolite studied mainly for helping preserve muscle you already have. Here is an honest, evidence-labeled comparison.
Renewal versus preservation
Urolithin A (UA) is a gut postbiotic your body makes from ellagitannins in pomegranate, walnuts, and berries, though only some microbiomes convert it efficiently. Its most studied action is supporting mitochondrial quality through mitophagy, the recycling of worn-out mitochondria. In muscle, that translates to a focus on cellular energy and endurance rather than on the size of the muscle itself.
HMB, short for beta-hydroxy-beta-methylbutyrate, is a metabolite your body produces when it breaks down the amino acid leucine. Its most described action is reducing muscle protein breakdown, which is why it is framed as a preservation tool, particularly during aging, bed rest, dieting, or other catabolic situations when the body is inclined to lose muscle. So one compound is about keeping the muscle's engines fresh, and the other is about defending muscle tissue from being torn down. They are not rivals so much as different levers.
Urolithin A: the human evidence, labeled
Proven in humans
UA has a real and growing human evidence base. The first-in-human study (Andreux and colleagues, Nature Metabolism, 2019) found UA safe and well tolerated up to 1,000 mg per day and identified a mitochondrial gene-expression signature in older adults. A randomized trial in older adults (Liu, D'Amico and colleagues, JAMA Network Open, 2022) reported improved muscle endurance over roughly four months. In middle-aged adults, Singh and colleagues (Cell Reports Medicine, 2022) tested 500 mg and 1,000 mg arms over four months and reported gains in muscle strength and exercise performance. For muscle-focused readers, this is the heart of the case, and you can go deeper in our page on urolithin A for muscle.
Newer human research
The evidence keeps expanding. A 2024 randomized controlled trial in resistance-trained men (Journal of the International Society of Sports Nutrition) examined UA over eight weeks, and a 2025 trial in distance runners added an endurance-athlete perspective. A roughly 28-day randomized study in Nature Aging (2025) reported that UA supported immune-cell mitochondrial health in midlife adults, connected to inflammaging. A 2024 systematic review in Ageing Research Reviews concluded, appropriately, that the evidence for targeting aging with UA in humans is still emerging. Our summary of the urolithin A clinical studies lays these out in more detail.
Preclinical foundations
The mechanism was mapped in preclinical models. Ryu and colleagues (Nature Medicine, 2016) showed UA stimulated mitophagy, extended lifespan in C. elegans, and improved muscle measures in rodents. Later preclinical work (D'Amico and colleagues, Aging Cell, 2022) examined joint and cartilage endpoints in osteoarthritis models. Uses in skin, gut, brain, and heart remain early and preclinical, still being explored rather than established in people.
HMB: what the research supports
HMB is one of the more studied sports-nutrition ingredients, typically used at around 3 grams per day. The most consistent signal is in preserving muscle rather than dramatically building it, and much of the interest centers on older adults and on catabolic conditions where muscle loss is a genuine risk. Meta-analyses in people over 50 have examined HMB's effect on muscle mass and strength, with results that are generally modest and sometimes mixed, and the ingredient tends to show more value when the body is under stress than in healthy, well-trained lifters looking for extra gains.
The clean contrast with UA is this: HMB is a defensive, anti-breakdown tool aimed at holding onto muscle tissue, while UA is a maintenance-of-the-machinery tool aimed at the mitochondria that let muscle work well. Neither is a treatment for sarcopenia, muscle disease, or any medical condition, and neither replaces resistance training, adequate protein, and care from a qualified provider. If you are managing a health condition or significant muscle loss, see your doctor rather than relying on a supplement.
Choosing, and stacking
If your priority is cellular energy, endurance, and mitochondrial quality with human trials specifically in those areas, UA is the more targeted pick. If your concern is protecting existing muscle during aging, dieting, or recovery from inactivity, HMB is the ingredient with a preservation-focused literature. Because their mechanisms differ, some people combine morning UA with HMB around training, but there is no human trial testing a UA-plus-HMB stack, so any pairing is personal experimentation rather than proven synergy. Talk with your doctor before combining, especially if you take medications or have a health condition.
To go further, read our full urolithin A guide, and if you are comparing finished formats and brands, our editors' roundup of the best urolithin A gummies is a helpful next step.
Frequently asked questions
Is urolithin A or HMB better for muscle?
They target muscle differently. Urolithin A supports the mitochondria inside muscle cells and has human trials in strength and endurance. HMB is studied mainly for preserving existing muscle, especially in older adults and catabolic states. The better choice depends on whether your goal is cellular energy or muscle preservation.
Does HMB build muscle?
HMB's most consistent evidence is for preserving muscle rather than dramatically building it, and it tends to help most when the body is under stress, such as aging, dieting, or recovery from inactivity. Results in healthy trained lifters are more modest.
Can I take urolithin A and HMB together?
Their mechanisms differ, so some people combine them, but no human trial has tested the pairing. Treat it as personal experimentation and check with your doctor first, particularly if you take medications.
What is the studied dose of each?
Urolithin A has been studied at 500 to 1,000 mg per day, with 1,000 mg at the top. HMB is commonly used at about 3 grams per day. SOMA HEALTH Urolithin A Gummies provide 1,000 mg per four-gummy daily serving.
Is urolithin A safe?
In its first-in-human study, urolithin A was reported safe and well tolerated up to 1,000 mg per day. Individual circumstances vary, so consult a healthcare provider before starting any supplement.
Do I still need to exercise?
Yes. Neither urolithin A nor HMB replaces resistance training and adequate protein. They are intended to support, not substitute for, the fundamentals of muscle health.
How long does urolithin A take to work?
In the trials, muscle and mitochondrial changes appeared over roughly four months of consistent daily use, so give it weeks to months rather than expecting an overnight effect.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This guide is educational and is not a substitute for advice from a qualified healthcare provider.
A clinically studied 1,000 mg dose of Urolithin A in one simple daily gummy — to support mitophagy, muscle strength, and cellular energy.
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