Our chromosomes have small substances on the ends called telomeres. Think of them as being like those little plastic tips of shoelaces. Every time a cell reproduces, that telomere gets a little shorter, just as the shoelace tip wears off with time. Once the protective covering on the tip is gone, your DNA and shoelace begin to fray and are much harder to use. That's what causes cells to stop dividing and growing and replenishing your body. The cell realizes that it is no longer helping the body and commits suicide (that's called apoptosis), which can contribute to age-related conditions.

But your body also has a protein—called telomerase—that automatically replenishes and rebuilds the ends of the chromosomes to keep cells (and you) healthy. However, lots of cells in your body don't have telomerase, meaning that many of them have a reproduction limit—thus putting a cap on how well your systems can be replenished. (Telomerase, by the way, is overactive in 85 percent of cancers. That makes sense, right? Rebuilding the aglet that allows cells to divide helps those cancer cells reproduce and spread.)

The amount of telomerase depends on your genetics, but we're now starting to see that we can influence the size of those little tips, the telomeres. For example, researchers have found that mothers with chronically ill children have shortened telomeres, indicating that chronic stress can have a huge influence on how cells divide—or fail to.

The implication is that if you can reduce the effects that stress has on you, through such techniques as meditation, you can increase your chance of rebuilding the telomeres and decrease the odds of having your cells die and contribute to age-related problems.

The telomeres of people who feel more stressed are almost 50 percent shorter than people who say they're less stressed. Since scientists have a rough idea what the average telomere length is for a specific age, they can estimate how much older the higher-stress group is biologically: a whopping 9 to 17 years. Just by thinking they were aging faster, they actually aged faster. « Collapse