QUESTION: What causes stress fractures in runners? Could a vegan diet be a factor?

ANSWER: A stress fracture is a small crack in the bone. It’s an “accumulation injury,” said Dr. Michael Terry, an orthopedic surgeon and professor of orthopedic surgery at Northwestern Medicine.

With exercise and everyday activities, and even our normal body weight, we are constantly putting stress on our bones.

But that isn’t necessarily a bad thing, since stress causes microdamage to our bones that our body naturally repairs, and that continual repair process helps to make the bones stronger.

However, “if you don’t give bones long enough to catch up, instead of getting stronger they’ll break down, and you accumulate enough injury that the bones can break,” Terry said.

The most common cause of stress fractures is overtraining to the point that your bones can’t heal. The chance of developing a stress fracture increases if you suffer from any condition that also affect bone health. Such conditions include amenorrhea, in which women stop menstruating, thyroid and parathyroid diseases, and renal diseases.

“You can get stress fractures anywhere in theory, but we see them most in the hips and bones of the feet,” Terry said.

He has seen teenagers who have developed stress fractures in their shoulders from throwing a baseball, “but most of the time it’s in the lower extremity,” he said.

Children and teenagers who are growing are also prone to stress fractures at their growth plates, areas of developing tissue at the ends of bones that are weak links in the bone, Terry said.

“As kids are growing up, especially when they’re starting to work out more and they’re getting stronger and heavier, because they have a growth plate, they have the increased susceptibility of having a stress fracture around the growth plate,” he said.

Terry noted that athletes on vegetarian or vegan diets can also be susceptible to stress fractures if they don’t get enough protein or certain nutrients.

“Vegans have to be real careful and supplement their diet so they get enough vitamin D and calcium,” he said. Seniors and those who live in northern climes may also be susceptible.

© 2019 The New York Times Company