Healthy white smile close up. Beauty woman with perfect smile, lips and teeth. Beautiful Model Girl with perfect skin. Teeth whitening. (The Minnesota Star Tribune)

A friend passed along a Coca-Cola ad done by a Belgian advertising agency with the tagline "Happiness starts with a smile." The commercial takes place on a cramped subway as people are boarding the train after a long day at work. Everyone is silent and keeping to themselves.

Suddenly, the camera focuses on a hired actor who randomly starts smiling while looking at his tablet, then begins laughing more and more. Everyone on the subway takes notice and starts smiling and laughing.

Smiling is a bonding agent. It builds bridges to other people around us. It keeps us from remaining aloof and separate from one another. It just goes to show you that smiling and laughing are contagious.

I read in Self magazine that 94% of Americans polled said they noticed a person's smile during a first encounter. People were less likely to notice others' bodies or eyes.

There are so many benefits to smiling and laughing. A genuine smile and laugh increase the production of serotonin, the happy hormone, and dopamine — feel-good endorphins that slow cortisol production and diminish feelings of stress, anxiety and depression.

Years ago, I saved an article from USA Today explaining that we learn in childhood "people skills" such as listening, remembering names and smiling. It is amazing how people's moods and words are misjudged because they look too serious. A smile shows that you like yourself, you like your current place in the world and you're happy with the people you are interacting with. You should commit to making others smile every day of the week. The first Friday of October was designated World Smile Day for just that purpose. It was created by commercial artist Harvey Ball, creator of the ubiquitous "smiley face," who believed that all of us should devote one day each year to smiles and kind acts.

Smiling and laughing provide a workout. One smile uses more than 16 muscles. During a bout of laughter, the body increases its oxygen intake, which is just as good as taking a few cleansing breaths. That's why smiling and laughing are my favorite exercises.

Researchers in Germany instructed a group of people to laugh on demand to measure their core muscles. The data showed that laughing enhanced core muscles as much as — and sometimes more than — when those subjects did back lifts or crunches.

Want another reason to laugh? Results from a California study published by the AARP showed the positive impact that laughter has on short-term memory. Participants were separated into two groups. The first group watched a 20-minute comedy video, while the second group sat in silence. Both groups were given memory-recall tests before and after the 20-minute period. The group that watched the comedy video scored much higher.

Even if you don't have anything to laugh about, you should force yourself to laugh. This is the finding of a study done at the University of Illinois that shows how smiling can influence your mood and outlook. Researchers divided people into three groups to observe their reactions to a humorous cartoon. The first group was asked to hold a pen in their hands. The second group was asked to put the pen between their lips, forcing a frown on their face. The third group held the pens between their teeth, forcing them to smile. Guess which group found the cartoon to be much funnier -- the third group.

The publication Bits & Pieces surmises from the AARP article that "If you smile, you'll find something to laugh about. If you laugh, you'll exercise your core, take in more oxygen and feel happy ... Laugh and be well."

At least six people have taken credit for this little poem, but it's worth sharing in any event.

"Smiling is infectious; you catch it like the flu.

"When someone smiled at me today, I started smiling, too.

"I passed around the corner, and someone saw my grin,

"When he smiled, I realized, I'd passed it on to him.

"I thought about that smile, then I realized its worth.

"A single smile, just like mine, could travel around the Earth.

"So if you feel a smile begin, don't leave it undetected,

"Let's start an epidemic quick and get the world infected!"

Mackay's Moral: Cover your mouth when you cough. Never cover it when you smile.

Harvey Mackay is a Minneapolis businessman. Contact him at 612-378-6202 or e-mail harvey@mackay.com.