For years, volunteers nationwide have been telling Points of Light that they are happier, healthier people as a result of making a difference in the lives of others. Now, scientists are catching up with what these points of light are telling us, demonstrating that the benefits are tangible — mentally and physically — and a reason why so many keep coming back to help. They just feel better when they put others first. And this is despite the fact that the nature of their work often puts them in close contact with people who are suffering from illness, victims of crime or natural disasters, homeless, lonely, despairing or even dying. How can that be?

Let’s start with looking at the difference between two words that are often used interchangeably: empathy and compassion. Empathy is defined as “the visceral or emotional experience of another person’s feelings.” It’s that moment President Bill Clinton referred to when he famously said, “I feel your pain.” When you see a person who is suffering greatly, and feel sad — almost a grieving feeling in the pit of your stomach, really — that is empathy. Compassion, however, is different. One must first have empathy to feel compassion — you first have to recognize that someone else is suffering and in need — then have compassion to stop and help that person.

And it is compassion and its physical effect on the brain that has been the subject of several scientific studies over the years that are worth sharing, courtesy of the American Association of Psychological Science:

A study by Jordan Grafman of the National Institutes of Health using MRI images of the brain showed that the part of the brain that lights up when one is experiencing pleasure (such as that death-by-chocolate dessert or a George Clooney movie) is the same part that lights up when we give money to charity. The “joy of giving” appears to be anatomically based in the brain.

Steve Cole of UCLA and Barbara Fredickson of UNC Chapel Hill reported at a conference at Stanford Medical School’s Center for Compassion and Altruism Research and Education that people who describe themselves as “very happy” have lower levels of cellular inflammation (which is related to stress levels and cancer risks). But they found that this was the case only if people were happy because they lived a life of “purpose or meaning,” as compared to those who lived “the good life” of material wealth.

A compassionate lifestyle may also help lower stress levels. Michael Poulin of the University of Buffalo found that stress didn’t predict mortality in those who volunteer, but it did in those who did not. The theory is that the good feelings derived from being compassionate are so pleasurable that they may protect against the ravages of stress. Similarly, Sara Konrath of the University of Michigan found that people who volunteered lived longer than their non-volunteering peers, but only if they were engaged in charitable, not self-serving, activities.

Dr. Cole also found that a lack of social connection is more harmful to our health than obesity, smoking or high blood pressure. In fact, social connection builds a stronger immune system; the same genes that are affected by social connection are linked to immune responses and lower inflammation. As a result, people who are more connected to others recover from disease faster, are less anxious and depressed, have higher self-esteem, and tend to live longer. Conversely, those who lack social connectedness often see declines in physical and psychological health and are more likely to engage in anti-social behavior, leading to further isolation and loneliness.

All of this confirms what we’ve known for ourselves for years: that points of light are healthier, happier people despite the circumstances in which they often find themselves — whether it is an ICU at the hospital, the devastation left by a natural disaster, or even just the quiet sadness of a lonely nursing home. Through it all, volunteers are able to keep a smile on their face, stay healthier and live longer. Compassion fuels them, both literally and figuratively.

No wonder 62 million volunteers gave at least an hour a week of their time to others last year in this country. They know what’s good for them — and now we have scientific proof.