What it does: your cells' tiny power plants, mitochondria, break down with age, and the crew that recycles the broken ones gets sluggish by 60. Urolithin A turns that recycling back up ¹. Because it's made by gut bacteria not everyone hosts, eating the food does nothing for the roughly half of readers who can't convert it ². The supplement produces the same blood levels either way ³.

The strongest signal is immune. Four weeks at 1,000 mg shifted the aging-prone CD8+ T cells back toward a younger profile ⁴. Behind it: hamstring strength up about 12% over placebo in middle-aged adults ⁵, leg endurance up about 17% in older adults ⁶, and heart-disease blood markers moving the right way ⁷.

Read the asterisks. Two muscle trials missed their pre-specified main outcome and hit on the secondary ones. The one trial without maker-affiliated authors, in trained runners, found no speed gain but easier recovery ⁸. Pooling all five, it didn't raise peak mitochondrial energy output or mitochondrial count ⁹. It recycles broken engines; it doesn't build more.

If you decide yes, here's the routine.

Buy these first. Resistance training twice a week moves the same muscle and immune targets, free. Creatine monohydrate costs about $30 a year with decades of evidence. Protein around 1.6 g per kg of body weight a day is the strongest diet lever against age-related muscle loss. Urolithin A is what you add once those are handled; before that, you're paying a thousand a year for the smallest move in the stack.

The arc, if you take it.

• Weeks 1–4: nothing felt; inflammation and immune-cell markers start to shift on paper ⁴.
• Weeks 8–12: leg endurance begins to budge, so you're less gassed at the top of the stairs ⁶.
• Months 4+: strength up ~12%, bike VO₂ up ~10%, on top of your training ⁵.
• Years: unmeasured. The longest trial is four months, so a decade is a bet on the mechanism, not the endpoint.