Bones tell the story
Diet, exercise critical in adolescence

February 5, 2010

By Mark Ferguson

Editor’s Note: OCN writer Mark Ferguson was a young lad when he was recruited in 1991 for a long-term bone density study being conducted at the U of S. Almost 20 years later, he had a chance to learn about the results.

A bone health study 20 years in the making has proven what researchers in the College of Kinesiology suspected - that diet and exercise during adolescence has life-long effects on bone strength and a person’s risk of osteoporosis as an adult. But some of the results, like how bones actually develop during this time, are a bit of a surprise.

The original idea for the pediatric bone mineral accrual study (PBMAS) stemmed from a journal article published by U of S researcher Don Bailey back in 1989, which showed that adolescent children have a high incidence of bone fracture. But he could not prove why this was happening.

“Now, in 2010, we have a much better idea why and it has everything to do with the interplay between bones and muscles.” says Adam Baxter-Jones, associate dean in kinesiology.

Baxter-Jones says the most important discovery has been in learning how bones develop. During adolescence, he explains, muscles grow first in anticipation of bone-growth. So, the more physically active kids are, the more muscle grows during adolescence, and subsequently, stronger, bigger bones develop. Eating habits play a big part too, he said, and it is not just about the amount of calcium a person consumes. The amount of fresh fruits and vegetables is equally important, as it affects the mineralization of the bone.

The phrase ‘bank more bone’ is used to describe the importance of building as much bone as humanly possible during a person’s growing years to reduce the risk of osteoperosis later in life. “The more bone one can accrue in childhood, the better,” says Baxter-Jones, who began working on the study in 2000 after being recruited to the U of S from England for his background in children’s health and longitudinal studies.

At that time, most of the original PBMAS volunteers from 1991 were still coming back for regular testing. Over 250 students from two Saskatoon elementary schools began the study and were tested on more than one occasion between 2002 and 2006.

Many of them have been tested again since then. The result is an exceptional amount of data for a longitudinal study, says Baxter-Jones.

“This many years of solid data from a sample of this size is amazing…these volunteers are the key to the study.”

The two schools asked to participate in the study in 1991 were Prince Philip and Alvin Buckwold. Kids in grades one to six were chosen because they could be tested leading up to adolescence. Although the sample is primarily white, middle-class kids from southeast Saskatoon, “knowing what healthy, white, middle-class kids look like is a good starting point,” he says.

Volunteers were originally asked to complete an evaluation. They were given a series of questionnaires to record dietary intake and physical activity levels, and went through physical tests that included measurements, skin folds, and finally bone scans of the entire skeleton, wrists, forearms, ankles and legs. A few parts of the original evaluation have changed since 1991, but the key indicators have remained, and based on data, there is proof that many kids are less active, consuming less calcium and other important nutrients, and not banking as much bone as when the study began.

“Were you physically active as a kid?” asks Baxter-Jones. “I mean, here I am preaching about this study and I drive my kids to school every day.

“Our concern is that children today are heavier, they have more fat mass and lower bone mass, and their activity levels are lower. And the link between activity levels as a kid and an adult, well, it’s continuous.”

 

Writer’s Note: While waiting for my evaluation last week, I ran into an old friend from Prince Philip School. Corey was a couple years older but we both volunteered for the study in 1991. We reminisced about our old playground, before the fort was taken down, before the shinny rink was ripped out, before the tire swings were removed and before the sledding hill was flattened. Who knew playing at recess was helping our bones, we joked.