Keep on the sunny side.

Everybody knows the adage that laughter is good for what ails you. But can a laugh every day help keep a heart attack away?

Researchers at the University of Maryland are taking laughter seriously after finding that it actually causes the endothelium, which lines our body's blood vessels, to dilate. This enables the blood to flow more freely and to promote better overall cardiovascular health.

"The old saying that 'laughter is the best medicine' definitely appears to be true when it comes to protecting your heart," says Michael Miller, M.D., director of the Center for Preventive Cardiology at the university's medical center and associate professor of medicine at the School of Medicine. "We don't know yet why laughing protects the heart, but we know that mental stress is associated with impairment of the endothelium. This can cause a series of inflammatory reactions that lead to fat and cholesterol build-up in the coronary arteries and, ultimately, to a heart attack."

In the study, researchers compared humor responses from 300 participants, half of whom had either suffered a heart attack or undergone coronary artery bypass surgery. After reviewing responses to a series of multiple-choice answers to find out how much people laughed in certain situations and to gauge anger and hostility, researchers found that people with heart disease responded less humorously to events in everyday life.

"The ability to laugh--either naturally or as learned behavior--may have important implications in societies such as the U.S. where heart disease remains the number-one killer," Dr. Miller says. "We know that exercising, not smoking, and eating foods low in saturated fat will reduce the risk of heart disease. Perhaps regular, hearty laughter should be added to the list."

If you are taking life too seriously, Dr. Miller suggests incorporating laughter into your daily activities, just as you should do other heart-healthy activities, such as taking the stairs instead of the elevator.

"We could perhaps read something humorous or watch a funny video and try to find ways to take ourselves less seriously," Miller says.

Previous research has demonstrated that laughter has a positive benefit on overall health.

"People become healthier from laughter," notes Judy Goldblum-Carlton, a humor therapist at the University of Maryland Hospital for Children. "It improves circulation. When you laugh heartily, every organ is being massaged, including your heart, lungs and digestive system. Headaches can just go away. When you laugh, the endorphins released make you feel this elation. It makes those big decisions seem so much less important."

How can you find ways to improve your sense of humor and add more laughter into your life? Humor therapist Goldblum-Carlton offers some creative ways to bring humor back into your everyday routine:

* Figure out what tickles your funny bone. Some people like slapstick while others prefer a more intellectual type of humor.

* Watch a funny TV show or rent a stand-up comedy video. Some like America's Funniest Home Videos while others prefer Bill Cosby or Jeff Foxworthy.

* Add comedy to your commute. Listen to a funny audiotape when driving to relieve road stress and, if possible, turn the cell phone off when you're in the car.

* Start a humor library. Clip funny cartoons, collect calendars, mugs, pictures, funny greeting cards, books, or anything else that makes you laugh. Post cartoons and calendars on your wall, so you can look at them often for a good laugh.

* Laugh with others. People laugh much more often when in groups, so watch a funny movie with some friends and share the laughter.