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Urolithin B — SacredBod supplement bottle (illustrative)
Supplement · Muscle & Mitophagy

Urolithin B

500 mg · vegan · gluten-free · 30 caps

Muscle lossWeaknessPoor exercise recoveryLow testosterone symptoms MusclesTestesMitochondria
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Overview Stacks Timing Related Research FAQs

What it is

Urolithin B is a metabolite produced by gut bacteria when they break down ellagitannins from pomegranates, walnuts, and berries. Unlike its better-known cousin Urolithin A (which triggers mitophagy), Urolithin B primarily activates mTORC1 to stimulate muscle protein synthesis and has anti-aromatase properties that may support testosterone levels.

How it works

Urolithin B stimulates protein synthesis in muscle cells by 96% through mTORC1 activation — comparable to insulin. It also inhibits the ubiquitin-proteasome system (reducing muscle breakdown), decreases MuRF1 and MAFbx (muscle atrophy genes), and has anti-aromatase activity that may preserve testosterone. In denervated muscle, it partially prevented atrophy.

Who should take it

Athletes and bodybuilders seeking muscle growth, older adults experiencing sarcopenia (age-related muscle loss), individuals with low testosterone, and those interested in mitochondrial quality control. Relevant for Indians given rising sarcopenia rates in aging populations.

Avoid / careful

Pregnant or breastfeeding women, children, individuals with hormone-sensitive cancers (theoretical anti-aromatase concern), those who prioritize mTOR inhibition for longevity. Side effects: Limited human safety data. Animal studies showed no toxicity at tested doses. Theoretical concern: mTORC1 activation may not be ideal for longevity purists who favor mTOR inhibition.

When to take it

Morning
Noon
Evening
Night

How to take it

With food
Empty stomach
Before food

FAQs

Frequently asked

How long before I see results?
Urolithin B has no human clinical trials, so timelines are extrapolated from animal data. Muscle effects might appear in 4–8 weeks if the in vitro mechanism translates. Combine with resistance training for best results.
Is it safe to take daily?
No human safety data exists. Animal studies showed no toxicity, but long-term human use is unstudied. Start with the lowest available dose and monitor.
What's the difference between Urolithin A and B?
Urolithin A triggers mitophagy (mitochondrial cleanup) via AMPK. Urolithin B stimulates muscle protein synthesis via mTORC1. They have opposite effects on mTOR — A inhibits it, B activates it. For longevity, A is preferred. For muscle building, B is preferred.

In plain English

A plain-English read of the literature behind this supplement. Not a clinical recommendation.

Key citations: PMID 5566634 (Urolithin B as regulator of skeletal muscle mass, 2017), PMID 28426090 (Urolithin B anti-aromatase properties, 2017), PMID 37237908 (Urolithin A vs B comparison in muscle cells)

Editorial notes

SacredBod's longer take on Urolithin B — context the structured blocks above don't capture.

Urolithin B is the muscle-building cousin of the better-known Urolithin A. While Urolithin A cleans up damaged mitochondria through mitophagy, Urolithin B builds new muscle tissue through mTORC1 activation — making it one of the most intriguing natural anabolic compounds discovered in recent years.

What the Research Shows

The landmark 2017 study (PMID 5566634) found that Urolithin B increased protein synthesis in muscle cells (C2C12 myotubes) by an astonishing 96% — exceeding insulin’s effect (61.5%). It achieved this through mTORC1 activation and decreased expression of muscle atrophy genes MuRF1 and MAFbx. In denervated (disused) mouse muscle, Urolithin B partially prevented atrophy.

Urolithin B also exhibits anti-aromatase activity — it inhibits the enzyme that converts testosterone to estrogen. This may help preserve testosterone levels, though the effect has not been confirmed in human studies.

India Context

  • Availability: Urolithin B is essentially unavailable as a standalone supplement on Amazon India. Products labeled ‘Urolithin’ are almost always Urolithin A.
  • Natural source: Eat pomegranates (anar), walnuts (akhrot), and berries — but gut microbiome composition determines how much urolithin you produce. Many Indians may not produce significant amounts due to low ellagitannin intake and microbiome differences.
  • Price: N/A for standalone Urolithin B. Urolithin A products cost ₹1,500–₹4,000.
  • Regulatory: Not a Schedule H drug, but synthetic urolithins are novel ingredients with limited regulatory history.

Dosage & Safety

  • Standard dose: No established human dose. Animal studies used 15 μM in vitro; in vivo doses extrapolate to ~500 mg/day.
  • Best time: Morning with food
  • Critical caution: No human safety data. This is an experimental compound. Urolithin A (with human trials) is a safer alternative for most users.
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