Apple

Everyone's heard about an apple a day. As one of the most popular fruits in America, it's easy to get people eating these fiber-rich, crisp and juicy fruits. And that's a good thing for health: A diet rich in apples has been associated with a host of health benefits, including weight loss, improved lung function, lower risk of stroke, cancer and heart disease.

But just because the humble apple is ubiquitous doesn't mean it's without some mystery as well. Read on to learn more about the fruit you've been eating for, well, ever.

Apple Allergies Are Pollen Allergies

When we think about food allergies, we're much more likely to picture peanuts, shellfish or even eggs. But mild apple allergies are not uncommon. Of note, experts believe that it's the birch pollen that's commonly found on the surface of a raw apple that causes a reaction, rather than a compound found inside the fruit.

Apples Are A True Diet Food

The high water and fiber content of apples mean that you'll feel full longer, despite few (about 95) calories in each one. But apples give you an extra, fat-blasting advantage: A compound in the peel called ursolic acid has been shown to help increase brown fat in mice and, in a separate study, was found to increase calorie burn and reduce obesity risk in mice.

Apples Are Diverse

The apple is the most diverse food plant in the world. According to food journalist and apple expert Rowan Jacobsen, there used to be 16,000 types of apples in the U.S. alone. A current review of USDA data puts the variety diversity at 2,450 types.

The Way We Eat Apples Wastes Almost A Third

As the video above demonstrates, eating an apple in a circular pattern around the core, wastes about 30 percent of the apple's flesh (or between 20 and 30 calories).

Apples Have A Lot Of Air

Unsubstantiated Internet rumor suggests that apples are 25 percent air, but the only study we could find put the figure at closer to 18 percent.