We all know that exercise keeps us healthy. But two new studies get more specific. They look at how exercise may lower the risk of two major causes of death cancer and stroke. One study says exercise may lower the risk for 13 types of cancer. Another says that middle-aged people can reduce their chance of having a stroke by exercising. First let’s talk about cancer. Steven Moore of the National Cancer Institute led a team of researchers to study more than 1.4 million people. The study looked at participants in 12 U.S. and European groups. These people reported on their physical activity between 1987 and 2004. The researchers looked at the occurrence of 26 kinds of cancer among the participants during, on average, the next 11 years. Many participants reported walking, running and swimming. The researchers took into account how long they exercised per week, what they ate, if they were obese and if they smoked.