We have a common expression in America, "an apple a day keeps the doctor away." The fruit is certainly a healthy snack. But now there's new evidence that a chemical concentrated in apple skin may prevent muscle weakening.
Researcher Dr. Chris Adams of the University of Iowa and his colleagues added the chemical, called ursolic acid, to food given to laboratory mice. "And what we found was, they got bigger muscles," he says. "They got muscle growth, and they got stronger. But what was even maybe more interesting was that, even though the muscles were getting bigger, the mice weren't gaining weight."
What Adams really wanted to know, though, was what effect ursolic acid would have in cases of muscle wasting.
Muscle atrophy, as it's also known, is a common result of starvation and a number of very serious diseases, including cancer, diabetes and AIDS.
"But even though muscle atrophy is very, very common and very serious, we don't have a medicine for it. And so that was our goal with these studies, was to try and address that problem," Adams says.
So, in another part of the experiment, mice were put on reduced rations, which causes some muscle atrophy. The mice who had ursolic acid added to their diet regained more muscle mass than a control group that didn't get the supplement.
"And it did this by helping two hormones that our bodies use to build muscle. And so by helping those hormones, ursolic acid reduced muscle wasting."
Adams said his team hasn't yet investigated whether ursolic acid would prevent muscle wasting, and he stresses that his research on mice may not apply to humans at all.
But there's reason to believe it might. Ursolic acid - which is found in the skin of pears and some berries, as well as apples - is also found in herbs used by some traditional healers in Asia and South America to treat diabetes. And in their experiments, the researchers injected mice with ursolic acid, which significantly reduced their blood sugar - a basic marker for diabetes.
Chris Adams and his colleagues at the University of Iowa and the veterans hospital in Iowa City publish their findings in the journal Cell Metabolism.