Urolithin A: What It Is, How It Works, and Why Your Gut Decides Everything

By Dr. Terry Simpson

Most people hear the name Urolithin A and think it belongs in a commercial about prostate health. It sounds like something a man named “Gary, 62,” would talk about while fishing. But Urolithin A has nothing to do with plumbing. Instead, it sits at the center of a new wave of longevity science focused on how our cells clean up old, broken parts.

As we age, our mitochondria—the tiny power centers inside our cells—start to slow down. They build up damage and stop working well. Eventually, this pile-up makes us lose strength and energy. That’s where Urolithin A comes in. It helps switch back on a process called mitophagy, which is basically the cell’s recycling program for old mitochondria.

Where Urolithin A Really Comes From

You cannot eat Urolithin A directly. Instead, your body makes it when your gut bacteria break down special plant compounds called ellagitannins. These are found in foods like:

• pomegranates
• walnuts
• berries
• green tea (yes, really)

Green tea is usually known for its catechins, but it also contains ellagitannins like strictinin. After you drink it, your gut bacteria break these tannins apart and create ellagic acid, which can later turn into Urolithin A.

However, this only works if you have the right microbes. And here’s the surprising part:

Most people do not.

Studies show that only 12% to 40% of adults naturally produce Urolithin A from food. Everyone else makes little to none because their gut bacteria simply aren’t built for the job.

How Your Gut Decides Everything

Your microbiome—the community of bacteria living in your digestive system—decides whether you make Urolithin A or not.

People who produce Urolithin A usually have:

• more diverse gut microbes
• special bacteria like Enterocloster and Gordonibacter
• the right genes inside those microbes to do the chemical conversion

People who don’t produce it (called “metabotype zero”) lack those bacteria or the gene pathways needed. Eating more pomegranates or drinking more green tea does not fix this. No diet, including keto or Mediterranean, has been shown to turn a non-producer into a producer.

This is why two people can eat the same food, and only one makes Urolithin A.

What Urolithin A Does in Humans

In older adults, researchers have tested Urolithin A supplements for up to 4 months. These studies show several encouraging results:

• muscle endurance improves
• inflammation markers decrease
• mitochondrial health markers look better

Even so, there are limits. Trials show no meaningful improvement in:

• walking distance
• ATP (cellular energy) production
• overall physical function

So the biology looks better, but major clinical outcomes have not changed.

What Happens in the Lab (But Not Yet in Humans)

Scientists also study Urolithin A in senescent cells—cells that have stopped dividing but still cause inflammation. In the lab, Urolithin A can:

• reduce senescence markers
• calm inflammatory signals
• restore mitophagy
• improve oxidative stress
• even strengthen circadian rhythms inside aging cells

All of this sounds exciting. However, these findings are from cell culture, not humans. They give us clues, not guarantees.

Food vs Supplements

You cannot get Urolithin A directly from food. You only get the precursors, and only people with the right gut bacteria turn those precursors into Urolithin A.

Supplements bypass the microbiome entirely and give everyone measurable Urolithin A, even non-producers.

Foods that contain ellagitannins include:

• pomegranates
• walnuts
• raspberries
• blackberries
• some teas, especially green tea

But none of these will raise Urolithin A levels if your gut bacteria cannot perform the conversion.

Is Urolithin A Safe?

Short-term human studies show that Urolithin A is safe and well-tolerated. Most people experience no side effects. When side effects do show up, they are usually mild digestive symptoms like bloating or softer stools.

What we don’t know:

• long-term safety
• pregnancy or breastfeeding safety
• multi-year use
• effects in chronic disease

In other words, the short-term data look good, but the long-term story hasn’t been written yet.

Should You Take It?

Here is the simple answer:

Urolithin A is biologically promising but clinically modest.

It improves certain cellular markers and may boost muscle endurance in older adults.

It does not reverse aging or change major health outcomes—not yet.

Supplements make the most sense for:

• adults over 60
• people with early muscle loss
• individuals who are non-producers
• those wanting to support mitochondrial health

But nothing replaces the basics:

• resistance training
• movement
• eating well
• sleep
• stress control

That is still the foundation of a longer, healthier life.

REFERENCES

(For the blog — as provided)

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