Urolithin A (UA) is a natural dietary, microflora derived, metabolite shown to stimulate mitophagy and improve muscle health in old animals and pre-clinical models of aging. UA was administered for 28-day in a first-in-human clinical trial to sedentary elderly subjects. Muscle biopsies were collected before the first dosing, and at the end of the 28-day period, under fasted conditions. Gene expression was measured by microarray. Gene-set enrichment analysis of the gene expression data showed that UA increased the transcription of mitochondrial related genesets. These observed effects on mitochondrial biomarkers show that UA induces a molecular signature of improved mitochondrial and cellular health following regular oral consumption in humans.