Telomeres are strings of unused genes at the ends of DNA strands. Their purpose is to protect the DNA from injury, and from unraveling during cell division.
Unfortunately, each time a cell divides a small portion of the telomere is removed. After a certain number of cell divisions, the cell runs out of telomeres and becomes senescent.
Telomeres can also be damaged by oxidative stress, as free radicals chip away at them. People with high levels of oxidative stress age faster and have a far greater number of senescent cells than those of the same age whose body is able to control free radicals.
Because in most instances brain cells (neurons) do not divide, cell division is not a cause of damage to their telomeres. But even in the brain, high levels of free radicals can erode telomeres, causing the cells to become senescent.
A special enzyme called telomerase can repair the damage done to telomeres. Unfortunately, our cells contain very little of this enzyme.
The good news is that an extract called astragalus has been shown to be a potent stimulator for telomere regeneration. Quercetin also protects and lengthens telomeres.