The phytochemicals in apples – especially in the apple peel – help to prevent cancer. For more about the specific phytochemicals and how they work to help prevent cancer, see:
Organic or not organic?
Since apples are one of the most contaminated fruits on the market, be sure to buy organic apples, especially since you want to eat the healthy peels (which are higher in pesticides than the rest of the apple). Source: EWG’s Shopper’s Guide to Pesticides which you can download from the EWG website.