Diabetes mellitus (DM) is the most common endocrine disorder, and with a very high development rate. There are two main groups of DM: type 1 DM (basically due to an insulin deficiency), and type 2 DM (basically due to insulin resistance, i.e.: there is plenty of insulin, but actually the cells are resistant to its action). Both types lead to both abnormal glucose and lipids metabolism, sub-clinical inflammation and higher oxidative stress. We will speak mainly about type 2 DM. Its genesis is multifactorial, but we can ascertain that the diet is the principal modifiable factor. The benefits of a healthy diet are not limited to its nutrient content, must also provide other protective factors against oxidative stress, metabolic syndrome, diabetes and carcinogenesis content especially in plant foods, called compounds bioactive, serving in the body that can promote good health. A diet with high intake of phytochemicals and rich in antioxidant capacity with polyphenolic compounds (as the Mediterranean Diet), is related to a decreased risk of DM.