Oxidative stress is a factor in many disorders and occurs when unstable oxygen-containing molecules outnumber antioxidants in the body, causing a toxic imbalance that damages the fats, proteins, and DNA within cells.
In one study, 19 men with type 2 diabetes took a placebo or 5 mg of resveratrol (the antioxidant polyphenol) twice per day. Researchers asked the men not to eat foods with high amounts of resveratrol, such as red wine and grapes, peanuts and berries.
After four weeks, while the placebo group had not improved, men who had taken resveratrol had far fewer signs of oxidative stress, and much higher levels of a protein that helps cells absorb and use glucose. Doctors said this is the first study in humans to show that resveratrol improves insulin sensitivity.