While most things are best taken in moderation, love is something you might want to give and receive freely this Valentine's day.

Being involved in a healthy, loving relationship is good for the heart, says Vanderbilt Heart and Vascular Institute cardiologist Dr. Julie Damp.

It's not known exactly why, however.

It may be that people who are married or in close, healthy relationships have lower levels of anxiety, are less likely to smoke, are more physically active and are more likely to have a well-developed social structure, Damp said in a statement this week.

"There is a theory that people who are in loving relationships may experience neuro-hormonal changes that have positive effects on the body, including the cardiovascular system," she said. Certain hormone levels in the body vary depending on the level of an individual's stress and anxiety. "This has not been proven, but the idea is that being in a relationship that is positive may have positive effects on your cardiovascular system over long periods of time."

In fact, studies show that stress kills, and loneliness proves deadly, too. And the loss of a loved one has been shown to literally contribute to a broken heart.

Conflict or negativity in a relationship increases the risk for coronary artery disease, Damp said.

A study at the Heart and Stroke Foundation of Canada found people in unhappy relationships have a sustained increase in blood pressure when they are with their partners. Yet people with mild hypertension who are in loving, supportive relationships show a decrease in blood pressure when they are with their partners.

There are different kinds of love, of course. It doesn't seem to matter who gives you the "Be Mine" hearts or the box of chocolates (which might also be good for you, by the way).

"The data suggests that being involved in any type of healthy, close relationship may have a lot of positive health benefits," Damp said.