Inflammation is like a fire in your body you cannot see or feel. "It's a smoldering process that injures your tissues, joints, and blood vessels, and you often do not notice it until significant damage is done," says Dr. Andrew Luster, of the Center for Immunology and Inflammatory Diseases at Harvard-affiliated Massachusetts General Hospital. The damage might show up as arthritis, heart disease, stroke, and even Alzheimer's disease.

However, inflammation is not evil per se. It has an important role in how your immune system keeps your body safe and healthy. "The goal is to keep inflammation in check and not let the fire run wild," says Dr. Luster.