An apple a day keeps the fat cells away? According to a new study, apples — particularly the Granny Smith variety — contain a high percentage of nondigestible compounds that may be helpful in preventing disorders associated with obesity.

Scientists at Washington State University say Granny Smiths' high amount of non-digestible compounds, such as dietary fiber and polyphenols, encourages the growth of friendly bacteria in the colon.  


Studies have shown that the balance of bacterial communities in the colon of obese people is disturbed. This results in microbial byproducts that lead to inflammation and influence the development of metabolic disorders, such as diabetes, that have been associated with obesity.

“We know that, in general, apples are a good source of these nondigestible compounds but there are differences in varieties,” said 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.”

Despite being subjected to chewing, stomach acid and digestive enzymes, the nondigestible compounds in apples remain intact when they reach the colon. Once there, they are fermented by bacteria, which benefits the growth of friendly bacteria in the gut.

The study showed that the tart green Granny Smith apples surpass Braeburn, Fuji, Gala, Golden Delicious, McIntosh and Red Delicious in the amount of nondigestible compounds they contain.

“The nondigestible compounds in the Granny Smith apples actually changed the proportions of fecal bacteria from obese mice to be similar to that of lean mice,” Noratto said.

“What determines the balance of bacteria in our colon is the food we consume,” she said. Re-establishing a healthy balance of bacteria in the colon stabilizes metabolic processes that influence inflammation as well the sensation of satiety.

The study was published in the October issue of the journal Food Chemistry.

Question for the food docs: Will this still work if the apple is covered in caramel?

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