The statement "An apple a day keeps the doctor away” has been around for almost 150 years, and for good reason. 

In fact, John Chapman (1774–1845), better known as Johnny Appleseed, wandered the 13 colonies spreading health and good will by planting apple trees. 

This is because apples have long been associated with a healthful diet. Munching down apple cores and seeds have been part of a regiment to fight parasites and worms for generations. 

The Apple core and seeds do in fact contain arsenic and cyanide, but it is an extremely small amount, and is classified as an organic form. This is why they have been associated with helping to fight those nasty critters in our guts.  Additionally, apples are low in calories and sodium, and high in fiber and Vitamin C

Another benefit to eating apples is that the skin of the apple does not get fully broken down in the stomach and makes its way to the intestines where it feeds our good bacteria, so it is supporting a healthy gut.