In healthy individuals, carbohydrates from food are broken down into glucose (a sugar), which circulates in the blood. In response, the pancreas produces insulin, which aids cells in either using the glucose or storing it as energy. But in some people, because of genetics, obesity, or a hormonal imbalance, cells become resistant to insulin's help or the body doesn't make enough insulin, leading to higher blood sugar levels. Untreated, diabetes can cause serious complications such as blindness, loss of limbs and decreased kidney function. It also significantly increases the risk of heart attack and stroke, which kill 65% of people with diabetes. Diabetic women under 50, in particular, are more apt to suffer a heart attack—perhaps because the disease cancels out the protective cardiovascular benefits of estrogen.