Polyphenols are the most abundant antioxidants in the diet and are widespread constituents of fruits, vegetables, dry legumes, chocolate, and beverages. The products manufactured from fruits also contain polyphenols in significant amounts. Typically a glass of red wine or a cup of tea or coffee contains about 100 mg polyphenols. Polyphenols or polyphenol rich diets provide significant protection against the development and progression of many chronic pathological conditions including diabetes, cardio-vascular and neurodegenerative diseases or osteoporosis. Our research is focused on the benefits of polyphenols extracted from the black grapes seeds (BGSP), Sambucus nigra or Aronia melanocarpa fruits by using as experimental model the streptozotocin-induced diabetes mellitus on the Wistar white rats. The results of our studies presented in this paper provide a current understanding on the biological effects of polyphenols and their relevance to health. The role of polyphenols in human health is still a less known area of research as polyphenols have proven to offer great hope for the prevention of chronic human diseases.