According to WebMD, natural apple juice does not cause constipation. Natural apple juice or eating apples in general helps control both constipation and diarrhea because apples contain pectin, which bulks up stools.
Apples aren't just used for treating constipation, according to WebMD. The peel of an apple contains chemical called ursolic acid that the body needs for both metabolism and building muscles. This acid, however, does not always find its way into apple juice. Apples also contain a chemical that helps kill bacteria, which is why some apple mixtures are used as a disinfectant.
WebMD notes that people use apples and apple juice to help soften and pass gallstones, prevent cancer, clean the teeth and treat warts. Additional studies must be done to rate apple's effectiveness for these and other uses.