Elite runner Lee DiPietro has done more than 30 marathons, six Ironman Triathlons and countless other endurance competitions.

But it wasn’t until 2010 that she realized how important those miles would be.

DiPietro had just lost her sister to suicide when she learned her husband had cancer, which required the tumor to be removed in a risky surgery.

In her new memoir, “Against the Wind,” DiPietro recalls her husband’s doctor saying to her, “So I hear you are quite an accomplished runner and triathlete.”

Now 57, the mother of two sons says she was initially confused why he would bring up such a thing with her husband’s life on the line. But then a “light went on,” and she realized he was saying she had the discipline to get past this next obstacle.

“Oh yeah, those races were really tough things to get through,” she tells The Post of her impressive list of finishes, including winning the women’s title at the Marathon of the Palm Beaches in Florida at age 50.

Months later, just as her husband was due to go under the knife to remove the cancer, her then-26-year-old son Tim almost lost his leg in an ATV accident in New York.

“It was one of those things like running a marathon: You keep getting to these points in a race where you feel like you’re hitting another wall and another wall. You just have to try and keep setting your mind and your pace and say, ‘I know this is painful, but I just have to take another step. And it will ease up again,’” says DiPietro.

During those difficult months, she still ran at least an hour every morning to help clear her mind.

“It reminded me that I was strong,” she says. “I am many things: a mother, a wife, a sister and a daughter. But being a runner and a triathlete has made me who I am.”