A Granny Smith apple every day may keep you slim: study

Granny Smith apples are rich in non-digestible compounds that keep the metabolism running. ©Lucky Business/Polyvore

Non-digestible compounds found in apples promote the growth of friendly gut bacteria, which stabilizes the metabolism and creates satiety. That's according to the results of a new study that singled out Granny Smiths as your best bet for gut health.

"We know that, in general, apples are a good source of these non-digestible compounds but there are differences in varieties," says food scientist Giuliana Noratto, the study's lead researcher. "Results from this study will help consumers to discriminate between apple varieties that can aid in the fight against obesity."

In the study, several kinds of apples were examined, but Granny Smith came out on top for having the highest amount of the compounds, besting Braeburn, Fuji, Gala, Golden Delicious, McIntosh and Red Delicious.

Researchers say their discovery could prevent several of the health problems associated with obesity, like the onset of diabetes, which is quelled by the anti-inflammatory components of a healthy bacteria balance in the colon.

"What determines the balance of bacteria in our colon is the food we consume," says Noratto, who noted that the non-digestible compounds in the apples changed the composition of fecal bacteria in obese mice to resemble that of lean mice.

The compounds include dietary fiber and polyphenols and they survive the entire journey through the gut, including stomach acid and digestive enzymes.

The study was published in the journal Food Chemistry.