People who run everyday do it to keep their hearts strong, spirits up and waistlines trim, but how many could guess that sweating it out on the treadmill may actually fight aging?
A new study in the journal Circulation, shows that vigorous exercise may be inducing a natural anti-aging effect that goes right down to our DNA.
"People who exercise have better health and live longer, however the mechanisms are not completely understood," said Dr. Ulrich Laufs, lead author of the new study and researcher at the University of Saarlandes in Saarbrücken, Germany "You'd be amazed at how little we know about the mechanism of exercise on the cellular level."
In his small study of 104 people, Laufs and colleagues found that 50-year-old adults who had exercised vigorously over a lifetime -- such as marathon runners or endurance athletes -- appeared biologically younger --sometimes decades younger-- than healthy people the same age who were not active.
The American College of Sports Medicine and other medical institutions agree that exercising can prolong life by protecting against diseases.
But research has not been able to point to an actual anti-aging effect in exercise, or detail exactly how exercise protects against some diseases even among people who are otherwise thin and healthy.
Exercise a Fountain of Youth, or Just Fountain of Health?
"As most people grow older they develop increase likelihood of developing chronic diseases such as heart disease and diabetes. People who exercise regularly have been shown to have a lower rate of developing those chronic diseases," explained Wojtek J. Chodzko-Zajko, a member of the American College of Sports Medicine and head of Kinesiology and Community Health at the University of Illinois at Urbana-Champaign.
"But individuals differ widely in how they age. I think we're a long way from understanding all of it," he said.
Laufs and his colleagues decided to tackle the problem by studying exercise's chemical influence on telomeres -- caps, that act as a sort of buffer at the end of chromosomes that protect DNA from damage. A young cell typically has long telomeres, but telomeres begin to degrade and fray as it ages. Older people typically have shorter telomeres in their cells. If telomeres in a cell are too short, the cell dies.
Detecting How Exercise Affects Your DNA
Laufs first did a series experiments with mice and showed the more the mice exercised, the more their body's biochemistry protected their telomeres from deterioration. The mice also helped researchers pinpoint exactly how exercise rejuvenates cells in the cardiovascular system.
The researchers then analyzed the blood chemistry of endurances athletes and non-active, but otherwise healthy people who were either in their 20s or 50s.
Human and mice endurance athletes of any age showed the same chemical signs that exercise was protecting their telomeres. But 50-year-old athletes had significantly longer telomeres than relatively healthy people their same age.
Despite the findings, Laufs and other scientists are hesitant to call exercise the fountain of youth.
Laufs said he can't prove that the association has anything to do with cause and effect: Did a lifetime devoted to exercise make the 50-year-old marathon runners biologically younger, or did these individuals inherit physical advantage to begin with that would have made them appear biologically younger and led them to exercise more?
"This type of conclusion cannot be made," said Laufs, especially because "the people we looked at in this study are kind of extreme examples. We chose these extreme examples because we wanted to look at the mechanism."
For the rest of us who don't run marathons until we're 50, exercise experts ask that we please keep trying.
"To a very, scientific level and an applied level there are really two tracks that we have to pursue. One is to understand the mechanisms by which exercise helps," said Michael E. Rogers, professor and Chair of Human Performance Studies at Wichita State University in Kansas.
"The other track is to take that knowledge to make it applicable to people," he said.
Rogers argues that science has already found ways to prolong life, but that many can't enjoy them because they didn't stay healthy through exercise in their older years.
"Exercise is not just about living longer, there's a difference between quality and quantity of life. We've gotten to the point with technology where we can extend someone's life long after they can be physically active," he said. "I don't think any one of us wants to live an extra 10 years supported by machines, we want to avoid that."