Urolithin A is a byproduct of human gut bacteria and dietary polyphenols found in pomegranates, berries, and nuts. Because diet, age, genetics, and disease affect the composition of the gut microbiome, people produce urolithin A at different rates. However, this compound is also produced in supplement form.
In animal tests and molecular studies on humans, it has been shown that supplemental urolithin A stimulates mitophagy, which is the process of breaking down failed mitochondria into elementary components that the cell can reuse. As we age, this natural process becomes less efficient, causing the body to accumulate many inoperable mitochondria. This is one of the reasons why our muscles become less functional as we age.
In the new study, scientists from the University of Washington (USA) studied a small group of people over the age of 65 who were randomized to receive a placebo or a daily supplement of 1000 mg of urolithin A for four months. From the outset, it was confirmed that each of the 66 subjects had a medium to low ability to produce adenosine triphosphate (ATP), which mitochondria produce to help cells perform many functions.
The researchers hypothesized that if urolithin A supplementation did indeed enhance mitophagy, the subjects would have improved muscle function and increased ATP release. This was only partially confirmed:
- Two measures of muscular endurance were improved in the group taking the supplement compared to the placebo group. Endurance was measured using exercises that engaged the first dorsal interosseous muscle between the thumb and index finger of the hand and the anterior tibialis muscle of the leg.
- Study participants who took the supplement had improved resistance to fatigue in the absence of exercise.
- Distance traveled during a six-minute walk improved markedly between tests at the beginning of the study and tests conducted four months later. However, this effect was observed in both groups and the researchers did not see a significant effect of supplementation compared to placebo.
- The indices (using magnetic resonance spectroscopy) of improvement in maximal ATP production did not change significantly over four months in both groups.
- According to the results of blood tests, a significant decrease in several acylcarnitines and ceramides, which play a role in metabolic disorders involving mitochondria, was observed in the study group.
Thus, although urolithin A supplements did not affect maximum ATP production, they did improve the subjects’ overall metabolism.
Scientists believe that urolithin A may benefit people who are unable to perform desired exercises due to poor muscle condition or illness. This is relevant both for people with chronic illnesses and for people who want to lead a more active lifestyle later in life. Supplements can help improve muscle activity at least to the point where a person can do minimal physical activity on their own, such as walking or climbing stairs.
Photos by Shutterstock/FOTODOM UKRAINE
Sophia Liu, Davide D’Amico, Eric Shankland, Saakshi Bhayana, Jose M. Garcia, Patrick Aebischer, Chris Rinsch, Anurag Singh, David J. Marcinek. Effect of Urolithin A Supplementation on Muscle Endurance and Mitochondrial Health in Older Adults. JAMA Network Open, 2022; 5 (1): e2144279 DOI: 10.1001/jamanetworkopen.2021.44279
