Like all parents, I tell my children that they must always tell the truth. “So why do I have to write a thank you letter to Grandma saying how much I love that set of monogrammed towels she gave me?” asks my ten-year-old son. “Can’t I say would have preferred a video game? It’s the truth.”

Leave it to a child to expose my hypocrisy. I fear the day he will interrogate me about Santa Claus and the Tooth Fairy.

The truth is, telling lies, even white lies, takes a toll on mental and physical health.  Frequent liars have increased stress, headaches, colds, back pain, insomnia and are more likely to be overweight than those who tell the truth. Lying is thought to trigger the release of stress hormones, leading to increased blood pressure and heart rate, among other stress responses that build up over the years.

The good news is that by telling the truth more often we can reverse this trend. A study showed that when participants purposefully reduced the amount of everyday lies they told they reported significant improvement in physical and mental health and better personal relationships. Just telling three fewer white lies a week made a difference.

Next time you are tempted to fudge the truth or spin an alternative fact about why you are late or forgot to return an email, consider telling the truth instead.

That said, as I tried to explain to my son, there are occasions when telling a white lie may be worth it, especially when it comes to sparing other people’s feelings.  He wrote a thank-you note saying how much he loved those monogrammed towels and also added a kernel of truth: “Now that I have a life time supply of beautiful towels, perhaps you will consider a video game next time.”

If you tell the truth, you don’t have to remember anything.

~Mark Twain