A chemical found in apple skin peel is associated with a host of health benefits from building muscle, halting weight gain and controlling blood sugar.
The chemical, called ursolic acid, found in the waxy skin of the apple, means that an apple a day could do wonders for all-round health.
On of the study researchers said: "Ursolic acid is an interesting natural compound. It's part of a normal diet as a component of apple peels."
"Muscle wasting is a frequent companion of illness and ageing.
"It prolongs hospitalization, delays recoveries and in some cases prevents people from going back home. It isn't well understood and there's no medicine for it."
In order to find ways to prevent this from occurring, he studied the genetic changes that occur when muscles waste or atrophy.
He checked a pool of 1,300 chemicals for one that would counter the changes - and found ursolic acid.
The researcher then supplemented a normal diet in mice with small amounts of the compound and subjected them to a range of health tests. The mices' muscles got bigger and their grip became stronger.
The benefits didn't end there. The mice fed the apple peel chemical had lower levels of cholesterol and other blood fats blamed for clogging up the arteries and damaging the heart, and had around a third less body fat.
It is thought that ursolic acid enhances the effects of insulin and insulin-like growth factor 1, two hormones key to muscle growth.
It is particularly concentrated in apple peel but is also found in cranberries and prunes and in basil, oregano and thyme.
The researcher said: "We know that if you eat a balanced diet like mom told us to eat you get this material. People who eat junk food don't get this."
"Given the current lack of therapies for muscle atrophy, we speculate that ursolic acid might be investigated as a potential therapy for illness-related and age-related muscle atrophy."
Research Paper Details:
Kunkel SD, Suneja M, Ebert SM, et al. mRNA Expression Signatures of Human Skeletal muscle Atrophy Identify a Natural Compound that Increases muscle Mass. Cell metabolism, 2011; 13 (6): 627-638.