A supplement sold for healthy aging met a placebo, and the main measure didn't move

Urolithin A is a compound made by gut bacteria and sold as a supplement for aging and blood-vessel health. A trial in JAMA Network Open put one of those claims to a controlled test.

At the University of Oklahoma, adults aged 40 to 64 with obesity took either 1,000 mg of urolithin A or a placebo every day for four weeks, with neither participants nor researchers knowing who got which. The main measure was how much the main artery in the arm widens, a test of blood-vessel function. The two groups did not differ meaningfully.

One secondary measure did shift. During a memory task, the urolithin A group showed larger blood-flow responses in a region at the front of the brain's left side. People did no better on the task itself, and a secondary result like this needs confirming before it means much.

The supplement was well tolerated, and more than 95% of doses were taken as planned. Still, the analysis covered 50 people, 74% of them women, at a single site for a month. It shows no health benefit, and whether that brain blood-flow signal leads anywhere would take a longer, larger trial to answer.