How good would it feel if someone just gave you $1,000?
Last fall, Oprah Winfrey thrilled audience members with these words: "You will each go home with $1,000."
Then she said there was a catch: "You have to spend the money on someone other than your family."
Winfrey said she wanted them to experience how good it feels to give.
They still applauded, but the smiles looked a little forced.
Yet maybe she did her audience a favor, because even though the audience had to give the money away, it could get back even more than they gave.
Stephen Post explains why in his new book, "Why Good Things Happen to Good People."
He reveals that new science shows giving -- money or time -- not only feels just as good as getting, but can actually improve your health.
"Giving is as good for the giver as it is for the receiver. Science says it's so. We'll be happier, healthier, and even -- odds are -- live a little longer if we're generous," Post said.
"Public health isn't just about bugs and staying away from lead. It's about doing unto others, and at the right dose, science says it's very good for you," he said.
Arthur Brooks, author of the new book, "Who Really Cares: The Surprising Truth About Compassionate Conservatism," also knows a lot about the current research on charity.
Brooks said, "There's evidence that it helps people with their asthma, in cardiovascular disease, weight loss, insomnia. When people have a lot of happiness, they do a lot better in their health as well."
That was true for former heart patients at Duke University Medical Center.
They were asked to visit current heart patients -- no particular agenda, just to listen and lend support. By doing that, the volunteers had better health after their heart attacks.
A similar study at the University of Miami by Dr. Gail Ironson followed HIV patients who volunteered, like Katherine Marshall Scott, who talks to teenagers about avoiding infection, and Stephen Baker, who counsels fellow HIV survivors.
These and other HIV patients who helped others had lower stress levels and higher immune resistance.
Scott's disease-fighting cells went up, from 200 to 800.
Baker says he could feel how volunteering improved his health.
"To get involved with someone else's problems makes your problems look a lot less," he said.
At least five studies show that seniors who gave tended to live longer, Post said.
After senior Fred Dekuyper started volunteering at a school, a small miracle happened.
"I used to walk with a cane all the time, and now I don't need the cane anymore," he said.
Many high schools require their students to volunteer.
It's called service learning. And oddly, even though the charity is forced, it still brings happy results. Teachers say students who volunteer raise their grades, and get higher SAT scores.
Abington High School student Jeff Rohrback said, "After service learning started, I got so involved into it, I started paying attention more, picked up my grades."
So "20/20" decided to see whether we could find a similar effect.
We put an ad on Craigslist recruiting people who were not currently volunteers. We introduced them to Post, and asked them to try it for one week.
But first, Post had them fill out a questionnaire that asked how they felt about life, like how often during the week they felt calm and peaceful.
Children for Children, whose mission is to get children involved in giving, agreed to help us, as did the Salvation Army, which has many different programs, from soup kitchens to after-school activities for kids.
Then off they went -- bringing donated books to children at an elementary school, then reading to the kids and making scarves with the kids. One spent time in a truck handing out food to the poor. All four worked at a Harlem soup kitchen.
One week later we had them answer that questionnaire again.
This time their answers about how often they felt "calm and peaceful" changed from some of the time to most of the time.
Post said, "In fact, just seven days of activity was a kind of a transformation."
One of our volunteers, Diana Sanchez was surprised at how strongly the experiences affected her.
"They were so grateful for me doing that, but it was just peas and carrots," she said.
When asked whether it had made her feel good, she said, "It did. It did."
Sanchez also spent time with kids at a Salvation Army after-school program.
"Just knowing that after work I was heading over to work with the children, just seeing them smiling -- that just made me feel so great," she said.
Researchers call that "the helper's high."
"The helper's high has been measured physically," Post said. "We know there's an actual physiological state. It's quite euphoric."
The helper's high shows up in MRI brain scans.
People who give money show brain activity that's associated with feel-good chemicals like dopamine -- the same brain activity that happens when you receive money.
National Institutes of Health neuroscientist Jordan Grafman showed us the brain scans.
"Those brain structures that are activated when you get a reward are the same ones that are activated when you give. In fact, they're activated more," he told us.
We asked our volunteers after their week of service who had gotten more out of the experience: the people they helped, or they themselves?
Volunteer Daniel Smith didn't hesitate with his answer. "No brainer. Me, definitely."
Lelani Clark also felt renewed from her single week of volunteering.
"I just felt energized," she said. "We were so caught up in this energy of helping that it was like a buzz -- like a spiritual buzz."
Winfrey's audience members reported that, too. After a week of giving money away, many said they were changed.
Maybe we should call it selfish to help others, because it seems to help the givers more.
"If you want to define selfishness so widely as to include the warm glow that people feel in the aftermath of selflessly giving to others, guess what, we need more of it, not less of it," Post said.
So try it.
Get out and give your money or your time. You'll help someone else. … And you'll feel good, too.
This story originally aired on December 1, 2006.