From a pragmatic perspective, one might say that married couples have an advantage economically. They may tend to share resources more readily and may have better access to health care. 

From a sociological perspective, perhaps married couples are more inclined to be involved in like-minded and supportive social groups such as church or charity involvement. 

From a legal perspective, people who are married have a vested interested in the health of their partner. The consequences of facing a long-term illness or catastrophic event could result in financial devastation. Helping one another eat healthy foods, exercise regularly, and wear seat belts and sunscreen, may be an act of love or even construed as "nagging." But there is certainly risk to one party when the other maintains reckless behavior. Therefore it is in our best interested to keep our spouses healthy! 

While all of these perspectives may have validity and contribute to the wellness benefit of marriage, I am not certain they truly get to the "heart" of the matter. 

In his book Secret Teaching of Plants, Buhner describes how we communicate via our heart center and details how all of our body systems resonate to the electromagnetic energy of the heart. Simple gestures such as understanding touch or taking a loved one's hand can send healing energy throughout the body. 

While this speaks to understanding the healing nature love relationships, it does not necessarily speak to the unique situation of marriage. Could it be that it is the commitment itself to another person to honor, respect, and consider their needs as greatly as we consider our own?