The Cellular Countdown

Each of your cells can only divide a limited number of times. The reason sits at the tips of your chromosomes: protective caps called telomeres that get a little shorter every time a cell copies itself.

After roughly 50 to 70 divisions, the caps wear down too far to shield the DNA underneath. The cell then stops dividing for good and enters a state called senescence.

Your Caps, Your Choices

Two people the same age can have very different telomere lengths. That gap can offer clues about biological aging, but it is a noisy signal, not a personal age meter that beats your birthday every time.

Things linked to faster telomere wear include chronic stress, broken sleep, and smoking. Things linked to slower wear include regular exercise and a steady, unprocessed diet. Day to day, your habits may help protect the conditions your chromosomes live in, even if they do not neatly edit the ends.