Warm and spicy, cinnamon flavors some of our favorite holiday baked goods. Historically, it's been used to treat indigestion. For people with diabetes, cinnamon may offer an extra benefit, although research has been mixed. One theory is that it acts like insulin, helping to control blood glucose levels. (Of course, cinnamon should be a complement to the main ways of treating diabetes — diet, exercise and medication — and not an alternative.)