The soybean seeds (Glycine max) originate from north-eastern Asian regions, especially China and Korea and, since its introduction to American colonies in 1765 (Hymowitz and Harlan 1983), its consumption has been worldwide spread. Soybeans are an economically important crop, which has been traditionally used for animal feed as well as for human food. In this field, soy has been a valuable resource for humankind by providing excellent proteins and other nutrients and, in many countries, soybeans and soy-based foods are considered as a staple food thanks to its low cost and high availability (Khetarpaul et al. 2004). Presently, in the market, there are several soy-based products and ingredients such as soy sauce, tofu, soy protein, soy-based beverages and fermented foods, like miso, tempeh, natto, etc. Besides the excellent nutritional properties such as the high protein content and the presence of polyunsaturated fatty acids, as well as the absence of cholesterol and lactose; soy has demonstrated to provide a preventive effect in the occurrence and development of several common diseases. In the developed countries, the incidence and prevalence of illnesses like diabetes, osteoporosis, cancer, or cardiovascular diseases, among others, are becoming highly important and some of them constitute the leading causes of mortality. Generally, oxidative damage, inflammatory responses or lipid accumulation as well as other more complex biochemical processes are involved in the disease development mechanisms. Scientific studies have revealed that most of these illnesses are strongly related to genetic and/or environmental factors. In this field, the diet has shown to play an important role in preventing the appearance or even reducing the associated symptoms. The lower incidence of these diseases in eastern societies, where the soy consumption is considerably high, remarks the importance of diet and highlights the beneficial properties of soy. Many of the soy benefices have been attributed to the occurrence of several kinds of phytochemicals, such as isoflavones, soyasaponins, phytates, or protease inhibitors. These bioactive compounds seem to provide a preventive effect by means of reducing or even inhibiting the mechanisms of the disease development. Hence, some of their most important properties, for instance, the antioxidant, the antiinflammatory or the estrogenic activities, may be involved in the disease prevention.