The Question: I’ve read various internet articles that say that human beings replace “every cell in your body” every X years (usually 7, but sometimes 10). What’s the real deal?
Submitted by: Rick, NY
The Short Answer: Recent research has confirmed that different tissues in the body replace cells at different rates, and some tissues never replace cells. So the statement that we replace every cell in the body every seven years or every ten years is wrong. Using a revolutionary new technique (described below), researchers have shown that:
Neurons in the cerebral cortex are never replaced. There are no neurons added to your cerebral cortex after birth. Any cerebral cortex neurons that die are not replaced.
Fat cells are replaced at the rate of about 10% per year in adults. So you could say that on average, human beings replace all their fat cells about every ten years.
Cardiomyocyte heart cells are replaced at a reducing rate as we age. At age 25, about 1% of cells are replaced every year. Replacement slows gradually to about 0.5% at age 70. Even in people who have lived a very long life, less than half of the cardiomyocyte cells have been replaced. Those that aren’t replaced have been there since birth.
Scientists are now studying other tissues to determine the turnover rate.
More Information: What’s a little confusing about the data given above is that obviously, our brains grow bigger after birth, and so do our hearts. So where is all the extra bulk coming from? In the brain, no cerebral cortex neurons are added, but research hasn’t been completed on other parts of the brain, and even if it were to turn out that no other neurons are added, lots of other kinds of cells are added. Glial cells, for example, may actually make up 90% of the cells in the brain. It used to be thought that glial cells were simply the scaffolding of the brain, with no real role in the processing of the brain. In recent years, however, it has become clear that glial cells play key roles in processing.
Cardiomyocytes are the true muscle cells of the heart, but the heart is also made up of connective tissue and other cell types that may turn out to have different growth and replacement rates. And while cardiomyocytes replace very slowly, and some are never replaced, the individual cells do grow in size.
The Interesting Science: The technique used to investigate the replacement of cells in humans ingeniously utilizes the unfortunate fact that during the Cold War the nuclear states conducted above ground nuclear tests that spread radioactive Carbon-14 all over the globe. Carbon-14 combines with oxygen in the atmosphere to form CO2. This results in a mixture in the atmosphere of CO2 formed with normal, non-radioactive Carbon-12 or Carbon-13, and CO2 formed with Carbon-14. This CO2 is then used by plants such as wheat and eaten by animals such as cattle. When we eat crops or livestock, the mixture of Carbon-12, Carbon-13 and Carbon-14 becomes part of our cells, and most importantly, part of the DNA formed when a new cell is born. Since the DNA is not replaced over the life of a cell, the Carbon-14 in a cell’s DNA when the cell is born is pretty much the Carbon-14 it will always have. Since we know how much Carbon-14 was in the atmosphere before nuclear testing, we know how much was in the air during the testing years, and we know how it was eliminated from the atmosphere after the Nuclear Test Ban Treaty outlawed above ground testing in 1963, it’s possible to estimate the turnover of cells.
For example, if a person born just before nuclear testing shows no Carbon-14 from the fallout years in his cerebral cortex neurons, that suggests that no cerebral cortex neuron cells were added after birth. If any new cells had been formed, they would have incorporated Carbon-14 into their DNA. If, on the other hand, a person born right at the peak of the fallout years shows little or no fallout Carbon-14 in his cerebral cortex cells, that would suggest that all the cerebral cortex neuron cells had been replaced. They would have incorporated non-radioactive carbon into their new DNA relatively recently, after most of the Carbon-14 had been washed out of the atmosphere. Otherwise most of them would have some Carbon-14 still in the DNA from when the person was born during the height of the Cold War.
This is a very much simplified version of what a team lead by Dr. Jonas Frisén at the Department of Cell and Molecular Biology at Karolinska Institute in Sweden has been doing. It is their studies that produced the estimates for turnover of cerebral cortex neurons, fat cells, and cardiomyocytes given above.
By the way, Dr. Frisén is very interested in tracking down the origin of the “We replace every cell every 7 or years” myth. If any readers have information on where they heard or read this idea, leave a comment on this page by clicking below and I’ll forward your information to Dr. Frisén.
An article about Dr. Frisén’s continuing research appeared in New Scientist on June 10, 2013:
Evidence for Cardiomyocyte Renewal in Humans. Olaf Bergmann, Ratan D. Bhardwaj, Samuel Bernard, Sofia Zdunek, Fanie Barnabé-Heider, Stuart Walsh, Joel Zupicich, Kanar Alkass, Bruce A. Buchholz, Henrik Druid, Stefan Jovinge, and Jonas Frisén. (3 April 2009) Science 324 (5923), 98.
Dynamics of fat cell turnover in humans. Spalding KL, Arner E, Westermark PO, Bernard S, Buchholz BA, Bergmann O, Blomqvist L, Hoffstedt J, N?slund E, Britton T, Concha H, Hassan M, Rydén M, Frisén J, Arner P. Nature. 2008 Jun 5;453(.
08 10th, 2010
98 Responses
Many Of Us Are Related | Says:
[…] Our atoms get changed: /do-we-replace-our-cells-every-7-or-10-years/ […]
Quora Says:
It is thought that ALL the cells in the human body are replaced every few years, how do we retain our memory if the same happens in the brain?…
There is an answer regarding the seven year-myth at this web page: /do-we-replace-our-cells-every-7-or-10-years/ Whether or not brain cells are replaced does not necessarily relate to how we can keep our memory, though, unless …
Bill Says:
“Every cell in the human body is replaced over a seven year period.”
I first heard this theory in several contexts developing around the growing natural foods movement in the late ;s early ;s.
It took hold on the public imagination at that time because the number seven resonated across many activities, and because of the implied idea of freedom from the past, of starting anew that was so much a part of the spirit of that era.
A related idea, which is beyond question, is that every human being on the planet is swapped out every 100 years or so, and yet a “body” like New York City, or Calcutta, with all of its cultural habits, innate point of view, economic routines, etc. continues without any particular citizen having participated in the decisions involved in how things got that way.
Each individual thinks of himself/herself as “being” American, “being” Indian, living in such-and-such kind of dwelling, adorning the body in this or that kind of clothing, exchanging pieces of paper for such-and-such goods and services, communicating across acceptable social distances by means of vocal symbols etc. while nobody alive had a hand in how America,
or India, or any other place, as they are, got that way in the first place.
When I think about this, I can’t help but recall Al Gore, at the close of An Inconvenient Truth, stating a question that future generations, faced with a severely deteriorated environment, might well ask of us:
“What were they thinking?”
“I don’t know, man, this stuff was running downhill when I got here…”
So when, and how, does change happen?
(Great site.
I am glad a Google search brought me here. I’m gonna keep you close.)
Thanks, Bill.
And thanks again for letting me know the captcha feature wasn’t working!
We Are All Related Says:
[…] Our atoms get replaced: /do-we-replace-our-cells-every-7-or-10-years/ […]
Balkrishna Panday Says:
A number of years ago I attended a lecture by Dr. Deepak Chopra, famous Yoga Mentor, Spiritualist, lecturer and of course a qualified
Alopath, settled in U.S.A. He categorically stated that we change all our body cells in a number of years, to the best of my memory. It may be worthwhile to contact him for his latest opinion on the subject in the light of latest research on this topic.
Beginnings. | 7yearproject Says:
[…] in your body regenerates within a seven year period. Now, after further research, I am assured that this is not the case. However, this intriguing idea – that we could essentially become a NEW person every seven […]
anon Says:
The method by which the discovery and the conclusion is made is rather speculative and not scientific. Nowadays using nanoscopes everything can be known in details, the life of the cell.
/blog/new-brain-cells-many-triggers-for-neurogenesis
Happy reading.
…sins of a father take 7 generations to be wiped out…. ?
Could be something there in interpretation.
manjula Says:
Watch “Deepak Chopra : Physical Healing, Emotional Wellbeing” on YouTube – /watch?v=_gJN7I0a9XU&feature=youtube_gdata_player
Aescalapius Says:
I’ve heard Eckhart Tolle say this– that all of the cells in the body are renewed every 7 years– several times in interviews.
I read this theory on page 266 of “The Complete Idiot’s Guide To Buddhism” by Gary Gech, though he said our skeleton was an exception.
arthur Says:
Well it is still amazing
whether you want it or not..
Even if we agree that Cortex neurons and may be some other type of cells turn out not to renew (or change their atoms) then we can make a simple calculation: For fun lets
hypothesise that cortex neurons plus unknown cells that dont renew are equal to the amount of brain cells that we have … wich is a lot (
~ 1 billion )… then they make up ~0,002 % of all the cells in our body .. but then is
it a valid statment that 99,somethingsomethig % of all the cells in our body regemerate
in every X years ?
Certainly, most of our cells regenerate all the time.
It’s the statement that all of them do that is in question.
And it’s the idea that you therefore aren’t the same person.
Personally, I don’t think you need to know that your cells regenerate to know that you aren’t the same person you were seven years ago or ten years ago.
Clearly, no one stays the same, even if the part of our body — our brain — that plays the largest role in determining “who we are” is one of the parts that regenerates the least.
Patrick Jane Says:
Richard Feynman in the essay “Value of Science” said something similar:
“It means that phosphorous that is in the brain of a rat – and also in mine, and yours – is not the same phosphorus as it was two weeks ago.
It means the atoms that are in the brain are being replaced: the ones that were there before have gone away.
So what is this mind of ours: what are these atoms with consciousness?
Last week’s potatoes!
They now can remember what was going on in my mind a year ago – a mind which has long ago been replaced.
To note that the thing I call my individuality is only a pattern or dance, that is what it means when one discovers how long it takes for the atoms of the brain to be replaced by other atoms.
The atoms come into my brain, dance a dance, and then go out – there are always new atoms, but always doing the same dance, remembering what the dance was yesterday.”
That’s a very interesting and poetic quote.
I don’t know what Feynman said right before this, but if what he’s saying is that molecules are continually being broken down and replaced, that’s mostly true.
DNA, however, is unusually stable and fairly well protected from that process.
And the question of whether we replace all our atoms over time is a little different from whether we replace all our cells, which is the way the statement is typically stated.
Timothy Gerhart Says:
Plz send references for Dr. Frisen’s work and others on rates of cellular regeneration.
There are references at the end of the article.
Sondra Says:
Read it in a Buddhist Catechism from the late 1800s.
Mentioned in a footnote, with no references.
From the 1800s?
That’s surprising.
Sam Richards Says:
These guys are claiming all cells regenerate … Didn’t think it was true so did a bit of research and found your page.
Thanks for the information!
So from reading all of this, we replace all our atoms all the time, but not all the cells? That seems very confusing. How does each atom and or cell remember things from many years ago, so 70 or 80 or longer,,,this is so intriguing. If most cells are replaced is the remembering done by fewer cells? Can we remember things from birth, before birth? Yes very intriguing indeed. The only thing for sure is that science can not yet explain everything, we are forever learning. The first time I heard the 7year thing was from the BBC 7 up program, when it started back in the 50’S I think. Just one more thing, if the atoms are replaced, but not the cells…how does that work? Or is it just that we can not explain it yet?
Not all our atoms.
The atoms that make up DNA tend not to be replaced once a cell is “born.”
That’s why we can use the radioactive measurement to measure when a cell was born.
The rest of the compounds in a cell probably are being broken down and rebuilt all the time, which is how the atoms get switched out.
Think of it this way, molecules are bumping into each other constantly, as well as bombarded by normal background radiation.
They get broken, pieces get broken off, sometimes there are other molecules that split target molecules, a molecule that absorbs some background radiation might get degraded, etc.
Often the molecule will snap right back together.
But if a carbon atom had gotten chipped off, the molecule may just grab any nearby unattached carbon atom, and the molecule still continues to be the same compound, but with a different carbon in that one spot.
I’m not saying that this is exactly what’s happening, but it’s something like that.
And it’s happening constantly, thousands or millions of times a second in every cell.
So, over time, even though the cell continues to function and continues to have all the molecules it needs to function, the atoms all get shuffled around.
But DNA in a functioning cell is a highly protected molecule.
It’s heavily coiled inside the nucleus, and protected by a sheath of proteins.
So it doesn’t get bumped much.
And therefore, the carbon atoms that are in a DNA molecule when it was first formed are to a very large extent, the same ones that will be there, in exactly the same place, 70 years later.
As to how cells “remember” and how the brain continues to be able to retrieve accurate (I should put that in quotes) memories when most of its parts are changing, that is definitely an area that is still being explored and studied.
Barbara Says:
I heard it a number of years ago on a recording “Magical Mind/Maqical Body by Deepak Chopra.
I subsequently learned it was not true, but heard it again just today listening to the recording “Jesus of Nazareth: Your Pattern for Postmodern Living” by
Fr. Joseph A. Tetlow, S.J., Ph.D.
Chris Says:
I was taught in school that the body replaces every single one of it’s cells by age 70. Thoughts?
lorianna Says:
C “if” our bodies rejuvenate….why do we keep the same diseases…diabetes, and others? Wouldn’t those diseases subside , change, ( better/ worse)?
Thank you all for the interesting topic.
Karin Says:
I don’t know who initiated the theory of the 7-year-total-body-renewal, but I could support a theory like that mathematically:
Let’s assume an “average” adult weighing 80kg. His body would contain about 16.2kg of proteins.
Considering the “recommended” (as per FDA 1989) intake of 80mg of essential amino acids per kg of body weight for a “healthy” diet, this 80kg average person would eat 6.4g of essential amino acids daily.
If those 6.4g of protein building blocks were used to “regenerate” body cells, it would take 2,531.25 days to “replace” all 16.2kg of proteins in that “average” body.
That equivalents to 6.93 years.
Purely mathematically speaking, though.
John Says:
In Life’s Rtchet, Peter M. Hoffmann states every atom in our bodies are replaced within 7 years.
Ginny Says:
Cells can only replicate in the environment they find themselves in. Wouldn’t you want your cells to duplicate in the healthiest environment possible?
Jan Novak Says:
Probably because the bones are replaced totally in 7 years, being the hardest material I guess someone assumed all other ones were earlier:
http://stemcell.stanford.edu/research/
Fiona Russell Says:
I have read that neurones are replaced even in the 9th decade of life…so think this is a good one to know and believe…all cells can be replaced.. just have to give them the optimal environment in to be replace with healthy cells…
John Boyd Says:
Can I just make the most obvious of all comments to this post?
“Do you look the same as you did 7 years ago?”
If your body was not changing with cells dying and regenerating on a constant basis then you wouldn’t age.
You would look like an 18 year old for your entire life or whenever your cells matured and stopped dying and being replaced.
Give me a break.
You do not have to be a scientist to figure this out, just look in the mirror, look at your own photos, look at your parents or if you really don’t believe it then go look at your grandparents and tell them that their cells are not being replaced and changed every day, let alone every seven years.
Unbelievable.
Anyone who doesn’t believe their cells replace every 7 years, please post your photos from today and 7 years ago and we will be the judge.
It is very scientific.
Jacob Hempel Says:
Two sources of the myth:
http://isites.harvard.edu/fs/docs/icb.topic765092.files/Radioisotopes.pdf
Youtuber Vsauce mentions it in his video:
Hi John, thanks for your comment.
The issue is not whether we change cells.
As you point out, we clearly do.
It’s whether we change every single cell in every part of the body … and to a lesser extent, over what time period, seven years or ten years.
The philosophical symbolism being that if you change every single cell, you aren’t the same person you were seven years ago.
The scientific evidence seems to be that we don’t change every single cell every seven years or ten years.
Some cells are replaced much more slowly than that, and some cells don’t seem to change at all.
To me, that doesn’t really affect the philosophical idea that we are different people than we were seven years ago, or ten years ago.
For that, as you say, all we need to do is look in the mirror, or look into our mind/heart mirror and realize we don’t think or act exactly the same way we did seven or ten years ago, either.
Jacob, thanks for the links.
I assume in both cases, you’re talking about the statements that the body’s atoms are replaced constantly (on page 232 of the pdf.)
The seven years statement is usually about cells, not atoms, but the philosophical point is still the same.
It’s the idea that if your cells/atoms are turning over so fast, then you aren’t the same person you were seven years ago.
Again, the scientific evidence seems to show that some cells don’t turn over, and the way we are able to tell this is because the radioactive atoms in their DNA aren’t replaced, either.
There’s no doubt that the vast majority of atoms and molecules in our bodies do get replaced constantly, however.
So the philosophical point is certainly still valid.
We definitely aren’t the same people we were seven years ago.
kianmer(From Iran) Says:
Ive read about this in one of the books that the schools force us to study (the book about Muslim being and Islam rules) as they were trying to prove the existence of God and soul(spirit) and heaven and etc.
but as my researches has shown to myself,according to studying and experiences and the most was of what Stephen Hawkings said: THERE IS NOTHING that you need to believe in…There is no God and No SOUL. SO BE GOOD AND DO GOOD
Janet Says:
In a smoking cessation class 20 years ago they told us that by quitting ‘now’ our lungs would be free of oxidative stress from our last contact with salt-Peter in 7 years.
Whole new lungs!
I chose to believe them and that made it easier to quit.
Since then, I’ve noticed a lot of 7s in the Bible.
7 squared. Multiples of 7s.
Resting the land every 7th year after a cycle of harvesting for 6 years seems to be a building block of faith ‘because God said so’ & a lot of his instructions in the OT turn out to be scientifically sound the more we investigate.
Shmitah year?
Thomas Litman Says:
Great thread, Tom! Your scientific explanation is much appreciated in demystifying the “myth of the seven”.
Just a footnote: our (human) cells constitute only a small fraction of our total cells, as our microbiome (the bacteria, vira and other microorganisms in our intestine, lung and skin) is a much larger part of us than our “own” cells are. And bacteria surely replicate at a much faster rate (a matter of hours!) than human cells, so strictly speaking: more than 90% of our cells (that is: including the microbiome) are replaced on a daily basis.
I have a quicker way to research this than writing a paper called Evidence for Cardiomyocyte Renewal in Humans:
Look at this tattoo on my arm that I got 20 years ago.
Research completed in under 10 seconds. Myth proven wrong, indisputably.
John Says:
Interesting. We agree then that cells are replaced. What hasn’t been
discussed is how this happens. It needs to be discussed at at all levels (Molecular and cellular) in order to be appreciated properly. How ever very basically. In order for a new cell to be made it needs essential building blocks. The body needs 90 essential nutrients in order to function ‘properly’. 60 minerals, 16 vitamins, 12 essential amino acids and 2 EFA’s. A New cell essentially requires the amino acids – the building blocks along with mainly the minerals to hold it altogether. See RNA Splicing, Protein synthesis, DNA,mRNA etc. As virtually everyone! and it more or less is everyone is in a nutrient deficient state then to measure how fast someone does on average regenerate cells or degenerate is purely subjective to the individual and their state of body function.
If they were eating optimumly and supplementing to get all the nutrients, avoiding toxins (impossible), not being stressed etc etc. the the body would be healing itself and regenerating much more efficiently. Telemere’s might not be getting shorter and we all could be living much longer!
stealthpaladin Says:
just a note, some research has been done showing neuron growth in recent years and bacterial migration of brain cells between hosts.
Hi Stealthpaladin, can you cite the research for me?
And what does bacterial migration of brain cells mean?
But what about atoms? If we drink a glass of water, we ingest atoms of hydrogen and oxygen. When we pee, out go atoms of hydrogen and oxygen along with other waste atoms. But are the atoms we send out the same ones that we took in? Other atoms in the body include carbon, nitrogen, phosphorous, potassium, sulpher, sodium, chlorine and magnesium. To increase the mystery, consider a scale model of a hydrogen atom. Put a golf ball in the center of your nearest pro football stadium and revolve a green pea around the outside at the speed of light. How much of it is golf ball, how much is pea, how much is space and how much is pure energy? Considering that our 50 to 75 trillion cells are each made up of trillions of atoms, all of which enter and leave the cells in the energy process called “life,” actual cell replacement becomes moot in the question if we replace our bodies every so often. Far more relavant are those eensy little energy fields called “atoms” that allow life to exist. And, of course, what identifies us is the molecules of DNA that don’t change as the atoms enter and leave. So the constant recycling of atoms or cells makes no change on who we actually are. That’s more the job of our ideas, our mystical, non-material side.
The nuclear weapon test is meant to measure atom by atom replacement in DNA, and the data suggests that for some molecules in some cells, i.e. DNA in some brain cells, there is minimal or even no replacement.
But as you point out, that doesn’t mean all the rest of the cell isn’t being turned over in terms of the atoms in all the other molecules.
And if you want to look at the level of protons and electrons within those atoms, I think we’re a long way from ever being able to determine whether there is turnover there.
I don’t think we need to know about the protons for this example. Atoms of oxygen, in only one example, go from the lungs to the blood to the cells for rejuvination. It’s kinda like saying when we feed a baby, the spoon stays the same but the food in it changes all the time. Fun thread. In my stadium example, I often ask, “Is the golf ball AWARE of the pea, or vice versa?” In out perception of perception, we would say “Of course not. They don’t have brains.” But if anything can exist outside of our perception, how would we know? Both the golf ball and the pea could have perceptive qualities we could never sense. After all, they do maintain their composure eternally, and we don’t really know why. We apply elaborate labels using our manner of perception, but rarely consider that other manners of perception could exist.
Are people actually suggesting a yoga mentor will have better incite into this debate?
Richard, perhaps you didn’t finish reading the article, or anything related to the method used in the study covered by the article. They cover atoms.
They tested for cell replacement by checking the atoms. If the atoms are not replaced they extrapolate that the cell in some matter has remained constant. (As stated in the article, this is very simplified, but the concept is valid) Checking atoms using their radioactive state information is pretty objective. If you are able to measure constant ratios and locations of these atoms you can objectively say that those atoms are constant, and in most cases the molecules too, therefore the cells most likely are also.
There are some parts of our body that remain fairly constant throughout or lives it seems.
I agree, Pat, that some atoms stay and some are transient. I wonder if they get along well, or are they like many tourist areas where the locals don’t like Snowbirds?