This thesis deals with the health enhancing potential of apples and examines their preventive effects on certain diseases. Apples are among the most frequently consumed fruits and thus enjoy great popularity due to their delicate taste and accessibility. In the first part of this thesis several nutrients of apples and their relevance for human health are listed. Apples are rich in macro- and micronutrients, such as carbohydrates, vitamins and minerals, but their distinctive phytochemicals in particular present a considerable contribution to the human wellbeing. Among these phytochemicals are first and foremost polyphenols, including quercetin, catechin, epicatechin, phloridzin, procyanidin and phenolic acids. Subsequently, the second part addresses the risk reduction for chronic diseases, such as cardiovascular disease and cancer, by means of the consumption of apples. Based on selected in vitro and in vivo studies the underlying chemical and medical mechanisms are scrutinized in detail. The results show that apple polyphenols have an antioxidant and antiproliferative effect. Additionally, the regular consumption of apples may prevent cardiovascular diseases, several types of cancer, asthma, neurodegenerative diseases and diabetes and improve intestinal activity.