Bad news for selfish bastards: A new wave of studies shows that altruistic people not only live longer; they also lead healthier, less stressful lives. "Researchers have all but proven that people actively engaged in supportive behavior reap their own rewards in mental and physical health," says Stephen Post, a professor of bioethics at Cleveland's Case Western Reserve University and co-author (with Jill Neimark) of Why Good Things Happen to Good People, out in May from Random House.

Biologists have long known that when we help others—whether by distributing outdoorwear to disaster victims or taking disabled athletes out on the ski slopes—our brains release the same endorphins responsible for a runner's high, inducing feelings of well-being, reducing stress, and even strengthening the immune system. Now, dozens of studies funded by the—ahem—Institute for Research on Unlimited Love, a nonprofit Post set up in 2001 to study benevolence, are turning up longer-term benefits. Scientists who observed volunteers over the course of decades concluded that anxiety and depression dropped significantly for those who gave help, even more than for those who received it. Elsewhere, altruistic people were shown to have more success in relationships. And people who volunteered were up to 63 percent more likely to live a longer life. "I'd argue with Billy Joel when he sings about the good dying young," Post says. "What we're finding is that actually the good tend to do a little better."

The key, it seems, is personal involvement. "I would never take anything away from someone who writes a check," says Post, "but there's no doubt that direct helpfulness, as long as it doesn't overwhelm the giver, has tremendous health benefits." So do it for your heart and your ticker.

Lend a Little
Microfinancing—making small, interest-free business loans to impoverished people in developing countries—is all the buzz. See firsthand what a difference it can make by investing as little as $25 at kiva.org, a San Francisco–based site that works with microcredit groups around the world to help entrepreneurs like Agnes Meseno Silei, who's seeking a grand total of $300 to start a beadwork business in Kenya. You'll choose your loan recipient (Kiva features photos and bios) and receive regular e-mail updates about his or her progress. And you'll likely get your money back within two years—loans are not guaranteed, but Kiva has a 100 percent repayment rate—just in time to reinvest and help someone else find economic independence.