Pomegranate compound 'could combat' complications of ageing

"Pomegranates slow down the ageing process by prompting cells to recycle and rebuild themselves, a study shows," The Daily Telegraph reports. But before you rush to stock up on the "food of the gods", the study in question only involved worms and rodents.

Compounds called urolithins are produced by bacteria in the gut when breaking down food such as pomegranates, nuts and berries. The researchers found that one of them in particular, urolithin A, increased the lifespan of roundworms by a half. They also improved muscle function in rodents (specifically, mice and rats).

Urolithin A seemed to improve ageing muscles by having an influence on the cells' mitochondria. These biological components are often described as a cell's battery as it is the part of the cell that converts food into energy. During the ageing process, there is gradual decline in mitochondrial function. The findings suggested that urolithin A causes cells to get rid of these damaged mitochondria and in turn, increase production of healthy mitochondria to replace them.

Whether similar results would be found for humans is not known, though clinical trials are now under way, with results expected in 2017.

Rather than just waiting until then, older people can improve muscle strength, as well as heart and lung health, through regular exercise. Read more about the importance of exercise as you get older.

Where did the story come from?

The study was carried out by researchers from the Ecole Polytechnique Fédérale de Lausanne and Amazentis SA biotechnical company, both in Switzerland. It was funded by the polytechnique and the Commission for Technology and Innovation. There is a potential conflict of interest as some of the authors work for Amazentis, a drug company that produces urolithin A.

The study was published in the peer-reviewed medical journal Nature Medicine.

Both the Daily Mail and the Telegraph wrote that it was not guaranteed that everyone might benefit from pomegranates, as some people do not convert the compounds into urolithins. While it is true that previous research found that some people do not produce urolithins, we still do not know if urolithins are beneficial for humans (only worms and rodents at the moment).

What kind of research was this?

This was a laboratory study that investigated the effects of compounds called urolithins on roundworms, mice and rats.

Urolithins are produced by gut bacteria from natural compounds called ellagitannins that are found in pomegranates, nuts and berries. The ellagitannins are first converted to ellagic acid in the stomach, and then gut bacteria finish the process. There appears to be variability between humans as to how many urolithins are produced, with some people not producing any at all.

Previous laboratory research has suggested that urolithins might have anti-cancer and anti-inflammatory properties, but their exact mechanism of action was not known. This study looked at the effect of different urolithins, including urolithin A, urolithin B and urolithin C on muscle function in roundworms, mice and rats. Whilst this can provide some insights into the effects of urolithins, the findings may not be directly applicable to humans.

What did the research involve?

The researchers fed roundworms different urolithins or ellagic acid from birth until they died and compared the results with roundworms fed a control diet. They then performed several experiments to determine how the urolithins affected the mitochondria, a part of each cell that transforms food into energy.

Follow-up studies were performed on mice and rats using urolithin A, as this had shown the most promise in the roundworm studies. The rodents were given urolithin A or a control for between six weeks and eight months. Muscle mass, body weight, running endurance and activity levels were compared. In the molecular analysis of muscles, the researchers looked at the level of mitochondrial turnover and function.

What were the basic results?

Urolithin A increased the lifespan of roundworms by 45% compared with control. Feeding roundworms ellagic acid had no effect on lifespan.

Muscle function in mice was improved with urolithin A. Feeding 16-month-old mice urolithin A daily for eight months resulted in a 9% increase in grip strength with no change in muscle mass. The mice also spontaneously exercised 57% more than the control mice. In another mouse experiment, urolithin A given for six weeks increased running endurance by 42%. In rats, six weeks of urolithin A increased running capacity by 65%.

The improved muscle function appeared to be due to urolithin A causing cells to eliminate damaged mitochondria and increase production of healthy mitochondria.

How did the researchers interpret the results?

The researchers concluded that urolithin A is likely to improve the quality of muscle cells for rodents. They say that this "holds promise for further development in humans as an innovative approach for improving mitochondrial and muscle function". In their press release they informed us that clinical trials in humans have begun, with results expected in 2017.

Conclusion

This was a mixed animal study that aimed to investigate the effect of compounds called urolithins first in roundworms and then rodents. Urolithins are formed during the breakdown of ellagitannins, which are found in pomegranates, nuts and berries. It was not known whether urolithins were just a waste product, or if they had any beneficial effects.

The study found that one of the urolithins in particular, urolithin A, seems to improve muscle function in rodents. We do not know conclusively why, but the results suggested this was due to improving the quality of the mitochondria by increasing the rate of destruction of damaged mitochondria and increasing production of healthy mitochondria.

Studies like this are useful early-stage research for getting an indication of biological processes and how things may work in humans, however, we are not identical and findings can't necessarily be extrapolated.

We now eagerly await the results of the clinical trials that are now under way to see if there are similar positive effects in humans, and also to assess the safety and required dosage.

Exercise recommendations for older adults (aged 65 or above) are broadly the same as for all adults, and recommend at least 150 minutes a week of activity, combining both aerobic and muscle-strengthening activities.