In December 2012, Ivan Fernandez Anaya was behind Abel Mutai in a footrace in Spain. When Mutai slowed down 10 meters before the finish line, Anaya didn't pass him; he pointed the way to the end of the course. Mutai had misunderstood where the end of the course was. Anaya could easily have passed the confused Kenyan and won the race. But he didn't. He practiced a random act of kindness — just like that random bumper sticker advises.

There are many such stories in sports, of course — like the young runners who carried a competitor across the finish line in the video below — and plenty more in life.

Just hearing about people doing wonderful things makes you feel good, doesn't it? And when you get a chance to do something nice for others, it brings with it all kinds of pleasant feelings.

Those warm-fuzzies don't just brighten your day. A variety of research says being kind to others improves your health.

It slows aging

When we do good things for others, the feel-good chemical that's released is oxytocin. You've probably heard of it before. It's the same stuff that helps babies bond with their caregivers. Oxytocin also reduces free radicals, which are one of the primary culprits behind aging. They damage cells in a process called oxidative stress. The more often oxytocin is released, the more free radicals it can suck up and the less damage to cells — aging — occurs.

In fact, that's one of the points raised by Dr. David Hamilton, author of "The Five Side Effects of Kindness" in a TedTalk below, as he explain how kindness affects the heart:

It reduces inflammation

Chronic inflammation is connected to a higher incidence of diabetes, heart disease and cancer. In a 2013 study covered in the New York Times, 80 people were asked about their lives and their white blood cells were analyzed. Here's how the Times described the results:

Volunteers whose happiness, according to their questionnaires, was primarily hedonic, to use the scientific term, or based on consuming things, had surprisingly unhealthy profiles, with relatively high levels of biological markers known to promote increased inflammation throughout the body. They also had relatively low levels of other markers that increase antibody production, to better fight off infections.

The volunteers whose happiness was more eudaemonic, or based on a sense of higher purpose and service to others — a small minority of the overall group — had profiles that displayed augmented levels of antibody-producing gene expression and lower levels of the pro-inflammatory expression.

It reduces pain

Doing good for others releases endorphins, along with oxytocin. Endorphins are our body's natural painkillers, so it makes sense that paying it forward would decrease aches and pains.

Interestingly, in a 2016 study, researchers found that taking acetaminophen led to a decrease not just in physical pain, but in empathy and compassion, further linking the connection between pain and caring for others.

It reduces stress and anxiety

Planting a tree People who regularly do volunteer work have nearly one-fourth the amount of stress hormones circulating in their systems than people who don't volunteer. (Photo: boonchoke/Shutterstock)

People who regularly do good things (like volunteer work, caregiving, working with animals or paying for someone else's coffee) have almost a fourth of the amount of cortisol — aka the "stress hormone" — circulating in their systems than people who don't.

A 2015 study at the University of British Columbia found that anxiety also was decreased by doing good. Clinical psychology professor Dr. Lynn Alden and her team recruited 115 undergraduate students with high anxiety and assigned them to three groups. One group was asked to go out to social situations and do kind things on a regular basis, one group was told to go out but not do anything, and a third was just supposed to record their days (no instructions of any kind). Anxiety decreased the most in the first group.

"We found that any kind act appeared to have the same benefit, even small gestures like opening a door for someone or saying 'thanks' to the bus driver. Kindness didn’t need to involve money or time-consuming efforts, although some of our participants did do such things. Kindness didn’t even need to be 'face to face.' For example, kind acts could include donating to a charity or putting a quarter in someone’s parking meter when you notice that it is blinking. Studies by other researchers suggest that it is important that the kind act is done for its own sake and that it not feel coerced or be done for personal benefit. Aside from that, anything goes," Alden said of the results of her study.

It makes for better relationships

A man and woman look into the the camera and smile. People with strong personal relationships with family and friends tend to be healthier than people who are more emotionally distant. (Photo: Monkey Business Images/Shutterstock)

The stronger your personal relationships (whether that's with family, friends or even animals), the healthier you are. As Hamilton, the author in the TedTalk above, writes on HuffPost:

Kindness reduces the emotional distance between two people, so we feel more 'bonded.' It’s something that is so strong in us that it’s actually a genetic thing. We are wired for kindness.

Our evolutionary ancestors had to learn to cooperate with one another. The stronger the emotional bonds within groups, the greater the chances of survival, so 'kindness genes' were etched into the human genome.

Kind deeds beget kind deeds and the benefits accrue

Expressing kindness and generosity doesn't just give us benefits in the moment. It has ongoing and magnifying effects. "Results suggest that positive emotions, positive social connections, and physical health influence one another in a self-sustaining upward-spiral dynamic," write the researchers in a 2013 paper about the influences of happiness on health.

“The practical implications of this positive feedback loop could be that engaging in one kind deed (e.g., taking your mom to lunch) would make you happier, and the happier you feel, the more likely you are to do another kind act,” Lara Aknin, the lead author of a study published in the Journal of Happiness Research, told Greater Good magazine.

So next time you're feeling down, try doing something for someone else. As the 2016 research in the journal Emotion points out: "People striving for happiness may be tempted to treat themselves. Our results, however, suggest that they may be more successful if they opt to treat someone else instead."

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.