Do We Replace Our Cells Every 7 or 10 years?

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:

  1. 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.
  2. 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.
  3. 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.

Update:  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, Näslund E, Britton T, Concha H, Hassan M, Rydén M, Frisén J, Arner P. Nature. 2008 Jun 5;453(7196):783-7.

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86 Responses

  1. Kevin Says:

    I read that in “A Short History of Nearly Everything” by Bill Bryson.

  2. winston Says:

    I heard the 7 years theory in the movie “waking life”

  3. rand om Says:

    i’m not religious, but i researched this and found references to releasing all debts every 7 years in Deuteronomy 15 (bible for those of you who don’t know)… My guess is the idea of our renewal of self might have a foundation in this.

  4. The cells of our body regenerate every 7 years. - Interfaith forums Says:

    […] cells of our body regenerate every 7 years. Ask a Do We Replace Our Cells Every 7 or 10 years? […]

  5. Ask a » Which Cells Are Never Replaced? Says:

    […] The Short Answer: So far, the only cell type that we can confidently say is never replaced is cerebral cortex neurons. Check out my posting a couple of months ago about the research of Dr. Jonas Frisén at the Department of Cell and Molecular Biology at Karolinska Institute in Sweden. Dr. Frisén has developed a very clever way to measure the replacement of cells in the human body. Like most careful science, this research takes time, of course. So far, Dr. Frisén and his team have only gotten definitive results on cerebral cortex neurons, fat cells, and cardiomyocytes (heart muscle cells). This research suggests that cerebral cortex neurons are never replaced. Fat cells are replaced fairly regularly, and cardiomyocytes are replaced at a decreasing rate with age. Click here for the full article: […]

  6. Jake Says:


    First of all, very interesting. I recall learning that our eyes, skin, and many other parts are replaced several times during the span of our lives. Would anyone be able to confirm this and possibly provide a rough estimate as to how many years it takes for eyes, skin and other organs to regenerate?

    Thanks very much in advance!

  7. Mandy Says:

    NEW NEURONS IN THE ADULT HUMAN BRAIN THROUGH THE PROCESS OF ADULT NEUROGENESIS. New neurons grow in the brain well into adult in the olfactory area and in the dentate gyrus of the hippocampus. These newborn neurons integrate into existing circuitry – and researchers postulate they may play a role in keeping memory details from overlapping, and in adding a new time component to old memories.

    Paradigm shift in Neuroscience – keep reading more by searching google scholar! neurogenesis and neurorehabilitation

  8. John Fee Says:

    I heard over 40 years ago at Nottingham Bible Institute (now defunct) from Rev H Brash Bonsall MA, BD (now deceased) – the founder and then Principal of Birmingham Bible Institute – that ‘every cell in your body is replaced every seven years, except the enamel on your teeth’. Mr Bonsall would not himself have been the authority for this statement, but he would have believed it to be the received wisdom of other reputable authorities at that time.

  9. Quora Says:

    Does an adult human keep cells or molecules from his/her newborn days?…

    The notion that every cell on our body regenerates every x years unfortunately turns out to be wrong. That makes me sad, because the thought of scientists researching how dying neurons transferred data to new ones was mouth-watering. I know for sure th…

  10. mfratlanta Says:

    George Bernard Shaw, in the Preface to the 1905 edition of his novel The Irrational Knot:
    “At present, of course, I am not the author of The Irrational Knot. Physiologists inform us that the substance of our bodies (and consequently of our souls) is shed and renewed at such a rate that no part of us lasts longer than eight years: I am therefore not now in any atom of me the person who wrote The Irrational Knot in 1880. The last of that author perished in 1888; and two of his successors have since joined the majority. Fourth of his line, I cannot be expected to take any very lively interest in the novels of my literary great-grandfather.”
    The ‘myth’ appears to be over 100 years old.

  11. bglassman Says:

    If one wants to chart myths, you might want to see what happens to the statement in “The Secret Life of Plants” that all human cells are completely replaced every 6 *months*!
    How good is the rest of the science-writing in a book that makes that kind of error? Of course, now I really want to read it.

  12. Communication with a Transsexual Cult – Final Transmission | Jade Hunter Says:

    […] being, we are actually able to use Google search and find out simple information such as that full cell replacement over seven to ten years is a myth. Have you taken a human physiology class? A basuc Health Class in high […]

  13. Self Portrait Loathing : David Spratte Says:

    […] looking to take shots of people out in the world. Either theirs or mine. It doesn’t matter. The average human body will regenerate most of its cells every 7–10 years. You’re a fundamentally different person every decade—I want to remember who these people […]

  14. Kim Says:

    I just heard the myth on the Mentalist tonight.

  15. Anon Says:

    This myth was repeated on the CBS TV show The Mentalist on 4/17/2011 in episode S03E19 at the 1 minute 8 second mark.

  16. Nothing About Potatoes | Things I found on the internet. Cannot guarantee 100% potato-free. Says:

    […] Puzzle On the subject of the body’s constituent molecules being replaced every seven years, some interesting things to consider are tattoos, memories, teeth, and ova. A proper scientific answer with real experiments and references and everything can be found here. […]

  17. Anonymous Says:

    My philosophy teacher told my class (while discussing personal identity) that all of our cells are replaced after seven years; however, some scientists contend that there are a few cells in the brain that are not replaced.

  18. Akamaiehu Says:

    The 2011 “Through the Wormhole 2, Is there life after death?” TV series that debuted 6.08.11 repeated the 10 year total body replacement (cellular renewal) claim–ironically enough, on the so called “Science Channel.”

    As with all claims brandishing the “Science” designation, caveat emptor. And for those who need a basic understanding of the critical difference between valid science and junk science, check our the “Baloney Detection Kit” on the Skeptic dot come website, here:

    Hope it helps!

  19. wamba7 Says:

    I recall being told by a physician that there are changes in the immune system every 7 years or so, which can trigger a change in allergic reactions. This could explain why I used to be able to roll in poison ivy patches wearing shorts and a T shirt without developing a rash. Nevertheless, I avoided it as I got older and so I didn’t exerience reactions.

    At some point in my 30s, I became aware that for me, the rolling around thing was no longer such a great idea – in short, I was no longer immune. At about the same time, though, I became “relatively” immune to hornet stings (I literally walked into a nest and was stung 15-20 times on my leg, causing only a little pain, numbness and swelling – my legs still worked well enough to get me away before I was stung more).

    But physicians are sometimes susceptible to fad science too, so I may have gotten false information. Maybe certain immune cells were just wiped out with age and not replaced.

  20. Mark Says:

    I dont know where the seven year replacement myth comes from, but I think there is some confusion about cells vs. atoms. There was a study done at Oak Ridge Lab. by Paul C. Aebersold in 1953 that found that 98 percent of all the atoms in a person’s body change out every year, and that within five years all the atoms had changed. Even cells that are not replaced, in the brain for example, must carry out some sort of activities and energy exchanges or they would die. Part of those processes results in the complete replacement of every atom in the cell. I found your article by accident while looking for a copy of the 1953 study. I found a copy, but do not want to pay the $32 for the right to read it. I did find a 1954 article from “Time” about the report. I posted the link below. And an unsourced quote from another article about the 1953 study I found on a blog.

    Unsourced quote from

    Studies at the Oak Ridge Atomic Research Center have revealed that about 98 percent of all the atoms in a human body are replaced every year. You get a new suit of skin every month and a new liver every six weeks. The lining of your stomach lasts only five days before it’s replaced. Even your bones are not the solid, stable, concrete-like things you might have thought them to be: They are undergoing constant change. The bones you have today are different from the bones you had a year ago. Experts in this area of research have concluded that there is a complete, 100 percent turnover of atoms in the body at least every five years. In other words, not one single atom present in your body today was there five years ago.

    URL for the Time article,9171,936455,00.html

  21. jack Says:

    I heard it in a philosophy class.

  22. P987 44 hari bersama cucu « Keluarga Sharif Yamah Says:

    […] kepada yang mengkaji. Ada yang mengatakan hayatnya 7 – 10 tahun (The ‘myth’ appears to be over 100 years old.), tetapi ada yang tidak bersetuju, seperti di atas. Cara pengukuran yang menarik perhatian saya, […]

  23. Katy Says:

    I heard the 10 years theory from my science teacher at school:/

  24. Elizabeth Says:

    I heard this nearly 30 years ago, I think, in an introductory philosophy class, in a discussion on the pre-Socratic view of essences and identity.

  25. heather Says:

    Read the ten year theory for the first time in old college notes of a family friend. This was somewhere between 1919 and 1921.

  26. viki Says:

    so eventually,what is it,7 or 10 yrs? i read about this over 30yrs. ago,but now i,me alittle mudled as to what to believe.

  27. jean marc Says:

    I just heard the 7 years theory in the movie Griff.The.Invisible.2010
    and here are the infos for the movie on wiki :
    also this post is from october 2010
    my question would be : any resent news ?

  28. Jerm Says:

    I read about the 7 year theory in a book by spiritual guru Anthony DeMello.

  29. Making Sense Out of Cell Replenishment | The Many Rants of Larry Russwurm Says:

    […] According to this article, fat cells are replaced in about 10 years. So maybe you can blame a 10 year marital itch on your fat. The more inconsiderate will blame it on their spouse’s fat. […]

  30. Anna Says:

    I read that US antrophologist John. E. Pfeiffer (* 1914) stated this “7-year rule” this in his book Human Brain (1955).

  31. Harry Says:

    I think I am almost quoting Richard Dawkins correctly from “The God Delusion” . . .Think of a strong memory from your childhood and realize that now not one of the cells (maybe he said atoms) still exists in your body today.

  32. Don Says:

    Most similar facts you hear with ‘7’ in them are made up. This could be because of the rumoured tendency of humans to favour the number 7. Or it could be that this is also one of the made-up facts!

  33. Trevor Clack Says:

    What about the ATOMS? bill Bryson said every atom in your body will be different. On each (well, most) of your cells, there’s a phospholipid bilayer. This layer is not static, rather, it moves around. The cell will undergo endocytosis, or exocystosis, gaining, or losing atoms, or organelles. So, I’m sure a cell that hasn’t divided for 30 years could have different atoms and thus in a way has replaced itself.


  34. Dr. K Says:


    The overall turnover rate of cells, in humans, in a year, is roughly equal to the total amount of cells at any given time (~3E14). In plain english: the ‘body’ is turned over once every year. Obviously so, perturbation of cellular homeostasis would result in significant recombosition of the body. Importantly, this quantification is cell-unspecific, as mentioned above. Certain cells have turnover rates that are very high (GI tract; turnover of 4-5 days) and others very slow, if at all (certain terminally differentiated neuronal cells). Notably, ~2.5E6 erythroblasts (red blood cell precursors) are produced every second (totalling a large constitutent of the total body turnover) and ~95% of these are sacrificed by apoptosis in the bone marrow before maturing and leaving the haematogenic system.

    In short, the notion that the body turns over every 7-10 years is unequivocally a misconception by the general population. Alternatively, the quantification could have orignally encompassed only a subset of cells. Arguably, the 10 year turnover originite from the turnover rates of bone: ~10% of bone turn over every year totalling a total turnover every decade.

    Several situations exist where normal hyperplasia singificantly increase turnover rate exist aswell; Following weaning of offspring the mammaries undergo involution resulting in apoptosis in 90% of the epithelial cells. In plain english: cells in breasts are increased in number by 1000% during pregnancy and turned over significantly more frequently. (Obviously, the breasts do not grow 1000% in volume during this time.) This turnover is of cells that normal breast do not possess. Another exmaple is hyperproliferation of tissue following damage: notably, the liver is the only organ that can compeltely regenerate (~5-10% of liver needs to be intact in order to grow back). Another example is following consumption of alcoholic beverages that denude cells in the throat greatly increasing turnover. Many more examples are readily available in the literature.

    For the interested (or academic): turnover rates are easily demonstrable by using 3H-thymine or 5-bromouracil pulse-chase assays in the Liberkühn crypts, for example.

    In conclusion, the entire notion is monumentally ambiguous and uninteresting. Turnover rates can only be described in a cell- and situation-specific context.

    Sincerely yours,
    Dr. K
    Cancer Biologist

    P.S. I stumpled upon this blog entry when I googled an Nature article containing the word ‘turnover’ (albeit in the context of a protein) in the title.
    P.P.S. Do not trust physicians when it comes to science. They are clinicians not doctors and only called doctors as a courtesy phrase.

  35. Tom Says:

    Certainly compounds lose and gain atoms all the time. And you’re probably right that most atoms in most cells, atoms in compounds get turned over frequently. Of course if that’s the level we’re looking at, then nothing on earth is ever stable. And why stop there? You could also say that the protons and electrons, or quarks for that matter, in everything are constantly turning over.

    Dr. Frisén’s research, however, suggests that in at least some cells, the turnover of atoms in DNA molecules is very low. Otherwise, the radioactive isotopes from nuclear fallout would have been incorporated in cells formed during the peak fallout years.

  36. My Seven-Year Itch | twenty-sided woman Says:

    […] that old adage that says we replace all of our cells every seven years. Turns out that’s not really true (though that’d make me feel better about my squishy memory – those cells were just reborn!). […]

  37. Tim S Says:

    I stumbled across this blog which asked the question about any evidence of cellular regeneration. While clearly some cells do regenerate, there are differing opinions on how and how often and if they all do!

    Here is an interesting study on the issue worth reading:

    Warm regards

  38. Consciousness, identity and tricks of the mind | Mr. Jaybird's Droppings Says:

    […] brain cells are never replaced play some role in maintaining the continuity of our consciousness? Read more about cell […]

  39. Consciousness, identity and tricks of the mind | Mr. Jaybird's Droppings Says:

    […] brain cells are never replaced play some role in maintaining the continuity of our consciousness? Read more about cell […]

  40. Quantum-Placebo-Effect Says:

    […] Here is the true story. Most (likely 98%) of your cells regenerate over a period of about 10 years (mainly because of fat cells; they take longer). Neurons in parts of the cerebral cortex never regenerate. DNA also does not regenerate. Cardiomyocyte cells in the heart regenerate at a degenerative rate, so that after your life less than half will have replenished. This means that it is mostly accurate that after a few years, you are almost an entirely new person. […]

  41. Best Self Improvement Blog Says:

    […] Here is the true story. Most (likely 98%) of your cells regenerate over a period of about 10 years (mainly because of fat cells; they take longer). Neurons in parts of the cerebral cortex never regenerate. DNA also does not regenerate. Cardiomyocyte cells in the heart regenerate at a degenerative rate, so that after your life less than half will have replenished. This means that it is mostly accurate that after a few years, you are almost an entirely new person. […]

  42. BECKY EVANS Says:


  43. We Are All Related : The paradox of atom replacement and identity « Family Survival Protocol Says:

    […] Our atoms get replaced: […]

  44. We Are All Related video Says:

    […] H Twins SCALE OF THE UNIVERSE (interactive): Our atoms get replaced: TIME article on atom replacement (pay-gate): […]

  45. Quora Says:

    Will human consciousness ever be transferrable to a computer?…

    Cortex neurons are apparently never replaced. Wonder why?…

  46. Homepage Says:

    … [Trackback]…

    […] Informations on that Topic: […]…

  47. Caralho, 10 anos de HBD! Acompanhe a retrospectiva | Hoje é um Bom Dia Says:

    […] perceber que eu era literalmente outra pessoa. Sim, literalmente — além do fato de que praticamente todas as células do nosso corpo são substituídas de 10 em 10 anos, o Israel Nobre de 2002 definitivamente não é o mesmo Izzy Nobre de […]

  48. Eddie Arnold Says:

    Doctor Alex Comfort who studied ageing and wrote a book on sex to earn some money mentioned the seven year theory pointing out that a trigger in later years stops perfect replacement. I remember David Attenborough being told by scientists the evolution was an unproven theory, so if we have evolved why would we have a perfect cell replacement system that for an unknown reason decides to fail. The Bible tells us that we are mortal and will live for as long as God says. 900 years in the early days decreased at present to 70 years and that if we care for each other and love our God we could earn eternal life. Eternal life being pointless if we insist on trying to kill each other so we can have more money to give us the power to oppress.

  49. hexalm Says:

    “I remember David Attenborough being told by scientists the evolution was an unproven theory”

    Nonsense, even if that’s what David Attenborough was told “by scientists” (which scientists? what kind of scientists?). Theories aren’t proven, it’s a matter of what best fits evidence. Actual evolutionary biologists would tell you that evolution has more evidence than many other theories–it’s very solid–and the fossil record hasn’t disproved it, for example by the order of fossil strata being incorrect.

    Our ability to replace cells is not perfect. They are all subject to damage. Ageing is under ongoing research, but genetic damage, and specifically telomere damage have been implicated as contributing to declining vigor with age.

  50. Tom of Says:

    Well, the idea that evolution is an unproven theory is technically true because no scientific theory is ever “proven.” As hexalm says, every theory is continually judged on how it fits and predicts the evidence. But the “theory” of evolution fits an enormous amount of the evidence we see in the world and no evidence has been found that conclusively disproves it. So, yes, it is an “unproven theory,” but it has far more explanatory power than any other theory about how the biological world functions and changes.

  51. Many Of Us Are Related | Says:

    […] Our atoms get changed: […]

  52. 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: Whether or not brain cells are replaced does not necessarily relate to how we can keep our memory, though, unless …

  53. 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 1960’s early 1970’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.)

  54. Tom of Says:

    Thanks, Bill. And thanks again for letting me know the captcha feature wasn’t working!

  55. We Are All Related Says:

    […] Our atoms get replaced: […]

  56. 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.

  57. 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 […]

  58. 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.

    Happy reading.

  59. amr Says:

    …sins of a father take 7 generations to be wiped out…. ? Could be something there in interpretation.

  60. manjula Says:

    Watch “Deepak Chopra : Physical Healing, Emotional Wellbeing” on YouTube –

  61. 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.

  62. Art Says:

    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.

  63. 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 ?

  64. Tom of Says:

    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.

  65. 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.”

  66. Tom of Says:

    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.

  67. Timothy Gerhart Says:

    Plz send references for Dr. Frisen’s work and others on rates of cellular regeneration. Thx.

  68. Tom of Says:

    Hi Tim. There are references at the end of the article.

  69. Sondra Says:

    Read it in a Buddhist Catechism from the late 1800s. Mentioned in a footnote, with no references.

  70. Tom of Says:

    Wow. From the 1800s? That’s surprising.

  71. 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!

  72. Sue of Says:

    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?

  73. Tom of Says:

    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.

  74. 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.

  75. Chris Says:

    I was taught in school that the body replaces every single one of it’s cells by age 70. Thoughts?

  76. lorianna Says:

    Curious ; “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.

  77. 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.

  78. John Says:

    In Life’s Rtchet, Peter M. Hoffmann states every atom in our bodies are replaced within 7 years.

  79. 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?

  80. 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:

  81. 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…

  82. 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.

  83. Jacob Hempel Says:

    Two sources of the myth:


    Youtuber Vsauce mentions it in his video:

  84. Tom of Says:

    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.

  85. Tom of Says:

    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.

  86. 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

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