Grapes contain many important vitamins and minerals, including more than one-quarter of the RDIs for vitamins C and K.Grapes are high in antioxidants, beneficial plant compounds that may protect against chronic health conditions, such as diabetes, cancer and heart disease.Compounds in grapes and red wine may protect against heart disease. Grapes may help lower blood pressure and cholesterol.Though grapes are high in sugar, they have a low glycemic index. Additionally, compounds in grapes may protect against high blood sugar.