By Isobel Whitcomb For The New York Times   “An apple a day” might seem like overkill, but America’s most popular fruit — currently weighing down branches in orchards everywhere — is packed with health benefits. Here’s what nutrition experts have to say about apples. They’re good for your gut Apples are rich in dietary fiber, a type of complex carbohydrate that our body isn’t capable of digesting on its own. That fiber acts as food for many of the bacteria species that reside in our guts. These bacteria have a powerful impact on our health, affecting everything from cancer risk, to weight, to mood. A diet high in fruits and vegetables, including apples, has been shown to increase the number of beneficial bacteria and decrease the number of harmful bacteria in people’s guts, said Marie van der Merwe, a nutrition scientist at the University of Memphis. That could lead to better overall health, van der Merwe said. Apples have high amounts of pectin, a dietary fiber that can help you maintain healthy cholesterol levels. (Johnny Miller / The New York Times) In addition, apples themselves contain a host of beneficial bacteria. (While this is true for all fruits and vegetables, one study found that apples have a greater variety of bacteria than most.) When you eat an apple, some of those bacteria may become part of your microbiome. The apple is “acting like a probiotic in addition to acting like a prebiotic,” van der Merwe explained. They’re heart healthy Apples have high amounts of pectin, a dietary fiber that can help you maintain healthy cholesterol levels. In a 2012 study, 160 postmenopausal women ate either 75 grams of dried apples (equal to about two medium-size apples) or prunes every day for one year. After six months, the women who consumed apples experienced a 13% drop in their total cholesterol and a 24% drop in “bad” LDL cholesterol, while the women who ate prunes experienced a 3.5% drop in total cholesterol and an 8% drop in LDL cholesterol. Apples are also one of the biggest dietary sources of polyphenols — tiny, health-promoting molecules that plants produce to defend themselves from the elements. Certain polyphenols in apples, called flavonoids, are particularly good at stimulating the production of nitric oxide, a gas that flows through our blood vessels, causing them to dilate. That’s good for blood pressure, said Nicola Bondonno, a postdoctoral researcher at the Danish Cancer Institute who has coauthored several studies on apples. Apples with honey and crushed walnuts makes a crunchy, tangy salad that’s a welcome bit of freshness on any table, any time of year. (Michael Graydon and Nikole Herriott / The New York Times) They can reduce chronic inflammation Polyphenols in apples can reduce inflammation — and, in turn, possibly help reduce disease risk. Researchers published a study in August that analyzed health data from more than 119,000 people collected over nearly 20 years, including records of everything they ate over a 24-hour period on five separate occasions. The study found that those who reported eating more than two apples a day in the meal logs had a 30% lower chance of developing chronic obstructive pulmonary disease later on. “We saw benefits even at just half a serving a day,” said Aedin Cassidy, the chair of nutrition and preventive medicine at Queen’s University Belfast and a study coauthor. The study found that the association between apples and COPD risk was also linked to a reduction in inflammatory markers. Here’s how to enjoy them Apples are most nutritious when you leave the skin on, Bondonno said: After all, it’s the skin that contains those powerful polyphenols (and much of the fiber). She added that you should wash apples thoroughly before eating them to avoid pesticide exposure. In general, a darker color apple will have a richer variety of polyphenols, van der Merwe said. But more important than selecting the deepest red apple you can find is eating different apple varieties, so you can absorb as many different polyphenols as possible, she said.