Urolithin A (UA) is a chemical by-product that is made by our bodies when we consume pomegranate juice, strawberries or walnuts. Johan Auwerx at the École Polytechnique Fédérale de Lausanne in Switzerland and his team wanted to investigate whether these foods are as beneficial to health as some have suggested, so they decided to test the effects of UA in rodents and worms.
When they gave UA to Caenorhabiditis elegans worms, the animals lived an average of 45 per cent longer. And when the team gave the chemical to elderly mice, they could run 42 per cent further. This improvement occurred in the mice without them building any more muscles, which suggests that UA improves muscle-cell quality, rather than quantity. When Auwerx’s team looked closer, they found that UA seems to improve muscle cells by triggering them to eliminate damaged mitochondria – the powerhouses of the cell. When these are purged, the remaining healthy mitochondria divide and multiply. This means that they can produce more energy and work more efficiently.
“The goal is to see if this could be a potential therapy for frail elderly people,” says Auwerx.
As we get older, our muscle function declines, leading to frailty and loss of mobility. Loss of muscle mass – called sarcopenia – is increasingly being seen as an important factor in ageing, prompting several researchers to look fortreatments that can protect or repair muscles.
Auwerx thinks that UA is the only chemical discovered so far that is capable of building better muscles: other experimental treatments focus instead on building more muscle. His team is now conducting a clinical trial of the compound in people to see whether it can reduce frailty as they age.
If UA affects mitochondria in both worms and rodents, the odds are that this might work for other mammals too, says Nate Szewczyk at the University of Nottingham in the UK. “The promise for this having an effect in humans is very real.”
Declining skeletal muscle mass and the resulting loss of strength are hallmarks of aging. These changes can become debilitating and lead to a condition termed sarcopenia, which is thought to affect 30% of those over 60 years old and greater than 50% of individuals over 80 years. Current estimates in the United States project there will be greater than 75 million adults over 60 years by the year 2020.
The resulting reductions in quality of life and independence as a result of muscle decline constitute a growing healthcare issue in the aging population. There are currently no pharmaceutical therapies to treat age-related decline in muscle function and sarcopenia. Nutritional strategies have had limited impact to date, and new scientifically validated solutions are urgently needed.
Upon consumption of pomegranate juice, compounds known as ellagitannins are broken down in the stomach and then transformed by intestinal bacteria into urolithin A. This biotransformation has been shown to vary widely across individuals, with some showing high or low conversion rates, while others have different compositions of microflora and are unable to perform the conversion. Consequently, supplementing individuals with products designed to deliver carefully calibrated doses of urolithin A can overcome this natur
So should you start guzzling pomegranates? Auwerx suggests that drinking pomegranate juice and eating more berries and nuts may be advantageous for health. However, team member Chris Rinsch estimates that a person would have to drink up to four large glasses of pomegranate juice every day to receive an equivalent dose of UA to that they gave to rats in their study.