An apple a day really can help keep the doctor away. Here's how.

A version of the famous proverb "an apple a day keeps the doctor away" first appeared in the United States in 1866 in a New Hampshire-based magazine called Notes and Queries. Though older iterations of it might exist in other parts of the world, few repeaters of the proverb in century's past likely understood the full extent of just how beneficial to health apples really are. 

But apples aren't necessarily unique among other fruits in all of the health benefits they have to offer. It turns out eating most any fruit or vegetable - along with other healthy foods, as part of a well-balanced diet - can similarly help to keep certain medical issues at bay. 

Are apples healthy? 

There are many proven health benefits that come from eating apples. A National Center for Biotechnology Information study, for instance, shows that regular apple consumption reduces one's risk of developing lung cancer. "Research has also shown that the presence of polyphenols in apples has helped the fruit consistently be associated with a decreased risk of heart disease and type 2 diabetes," says Abbie Gellman, a registered dietitian and New York City-based chef.

Apple peels are also a great source of flavonoids, which help the body fight off viruses and inflammation and have been associated with a decreased risk of stroke. 

Apples are also rich in vitamin C, "which helps destroy free radicals before they can damage cell membranes, DNA, and other body components," explains Jill Weisenberger, MS, RDN, a Virginia-based registered dietician and author of "Prediabetes: A Complete Guide." She adds that apples contain pectin as well, which helps lower LDL cholesterol levels.

"Apples are high in fiber and antioxidants, which can help promote health and reduce risk for disease," says Abby Langer, a clinical nutritionist, registered dietitian and founder of Abby Langer Nutrition. "They're also good sources of carbohydrates, which gives us energy," she adds.

Eating apples can also help with healthy weight management because the snack is refreshing, satiating, low in calories, and "eating one can replace snacking on donuts, chips or ice cream," says Weisenberger.

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Are apples healthier than other fruits? 

Despite all their benefits, it wouldn't be accurate to describe apples as necessarily being "healthier" than other fruits. "All fruits are nutritious, and the most nutritious diets will provide a large variety of fruits," offers Weisenberger. For examples, she notes that pears have more fiber than apples, oranges have more vitamin C, and blueberries have a different mix of polyphenols. "That’s why eating a variety is the best way to go," she says. 

Langer agrees, so she says you shouldn't feel limited if apples aren't really your thing. "Choose whichever fruits you prefer to eat regularly," she advises.

Which apples are sweetest? 

It might surprise you to know that there are over 7,500 varieties of apples grown worldwide, according to research from Washington State University. Some of the most popularly purchased varieties within the United States include Fuji apples, Red Delicious, Golden Delicious, Honeycrisp, Pink Lady, Jonagold, Gala, Macoum, McIntosh, Empire, and Granny Smith. 

While sweetness levels can be subjective, Fuji apples are often considered the sweetest apple variety out there, followed by Gala, Honeycrisp, and Red Delicious. "Granny Smith apples tend to be less sweet and tart and hold their shape well, which makes them great for baking," says Gellman. 

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When it comes to health benefits associated with each variety, "don’t let anyone tell you one apple is healthier than another," advises Weisenberger. "Some will have more dietary fiber, but others will have more vitamin C," she explains. "My best advice is to eat what you like, keep the skins on, and periodically try a different variety."