You may have just celebrated your 30th, 50th, or 75th birthday,
but the cells that make up your body are actually much younger
than that. If you go by the numbers, your cells are, on average,
around 10 years old, or less.
Your entire skeleton regenerates about once every 10
In fact, most of your body's cells are constantly being replaced,
although its DNA stays the same from the moment the cell is
first created (by its parent cell dividing).
Because of this, Jonas Frisen, a stem cell biologist at the
Karolinska Institute in Stockholm, was able to develop a method
to determine just how old your cells really are.
"Dr. Frisen recalled that the nuclear weapons tested
above ground until 1963 had injected a pulse of radioactive
carbon 14 into the atmosphere. Breathed in by plants worldwide
and eaten by animals and people, the carbon 14 gets incorporated
into the DNA of cells each time the cell divides and the DNA
is duplicated," writes author Nicholas Wade in his New
York Times article "Your Body is Younger Than You Think."
Dr. Frisen was able to determine cells' ages in various tissues
based on their extent of carbon 14 enrichment. His findings,
published in Cell, revealed:
Cells from your rib muscles last an average of 15.1 years
Cells in the main body of your gut are about 15.9 years
old (the cells lining your stomach, meanwhile, are known
to last just five days)
What influences the rate of your cells' regeneration? It
depends on the cell's function in your body and at least partly
on how hard it must work. Your epidermis (skin), for instance,
gets renewed every 14 days because it's constantly being assaulted
by outside elements.
What are the regeneration rates of other cells in your body?
Your red blood cells last about 120 days, on average
Your liver regenerates completely every 300 to 500 days
Your entire skeleton is replaced about once every 10
Does Your Brain Regenerate?
In the past, it was believed that your brain cells did not
regenerate. And Dr. Frisen did find in his study that cells
from the visual cortex area of the brain did not appear to
However, brain cell regeneration, or neurogenesis, in humans
was discovered in 1998 by Fred Gage of the Salk Institute
in La Jolla, California and his colleagues. They found that
new neurons are created in the hippocampus, a brain region
involved in memory.
Want to grow new brain cells? Physical exercise is
one of the best things to help you do it.
So it seems that even certain areas of your brain are capable
The cells in your body that are thought to stay with you
for a lifetime (and do not regenerate) are, in fact, quite
limited and include:
Why Don't Your Cells Keep Regenerating Indefinitely?
Since your cells are constantly forming anew, it would seem
that we would all live forever. It doesn't work this way,
however, because a cell's parent DNA is translated to the
new cells. Over time, mutations in your DNA may develop, and
those mutations get passed on.
Meanwhile, each time a cell divides, the telomere caps on
chromosomes get shorter, which limits the number of times
a cell can divide.
What can you do to keep your body's cells in top condition
for as long as possible?
An excellent first step is to get regular
physical exercise. Gage found that exercise is one
of the best ways for adults to grow new brain cells.
Gage also found that staying active mentally -- by reading,
doing crossword puzzles, learning new things, working
part-time and socializing -- can also help you to keep
your brain cells strong.
What about the rest of your body? The keys to keeping your
cells healthy are the same ones that will keep YOU healthy:
You Only Have a Limited Lifetime Supply of Energy? The Latest
on this Theory
to Prevent Alzheimer's: The Most Effective Ways to Avoid this
Rapidly Increasing Disease
Vol 122, 133-143, 15 July 2005
New York Times August 2, 2005
February 15, 2007
May 28, 2005