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  • Who is Pritikin? See Engineering a Cure. What’s the puzzle? See Developing an Ex Vivo Cancer Proliferation Bioassay and Prostate Versus a Plant-Based Diet. What’s the big deal about IGF-1? See IGF-1 as One-Stop Cancer Shop and Cancer-Proofing Mutation. The binding protein findings may explain the conclusion in Is It the Diet, the Exercise, or Both?. As I covered in my full-length 2012 presentation Uprooting the Leading Causes of Death, tomorrow’s video-of-the-day How Plant-Based to Lower IGF-1? will go a level deeper and explore why eating plants lowers IGF-1.

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    • HemoDynamic, M.D.

      Life is the pursuit of balance not happiness; for, finding balance brings happiness.

      So where is the balance of IGF-1?  For finding this would bring reduced rates of cancer and increasing happiness for so many.

      As for now I think this will remain a rhetorical question. 

    • Mike17554

      What about vegan children?  If IGF-1 is so important for growth, are vegan children at risk of slow growth?  Are vegan children statistically shorter, lower in weight, or underdeveloped?

  • Jo


    •  I know–gives me goosebumps!

      • HemoDynamic, M.D.

        Just like quitting eating meat Cold Turkey!  Gave me Goose-Bumps

        • Jo

          I did it cold turkey too! It was my New Year’s resolution for 1994. Had Popeye’s fried chicken on New Year’s Eve, turned lacto-ovo on New Year’s Day, then lacto (no milk, but cheese), then vegan in 2000. I’ve had accidents, but have never cheated.

          Meat free since midnight ’93!  ;)

  • Chuck V

    I think this might have been addressed by the fact that longer term veg eaters blood appeared to have the same effect on cell death, but I’m curious if there isn’t a possibility that after several weeks the lower IGF-1 levels achieve a new steady state and another mechanism might impact cancer cell growth.  Would the same increase be seen in lower term studies if IGF-1 was added back at that point?

  • Another one for the good guys.

  • matchalover

    Dear Dr. Greger,
    THANK YOU for all your efforts in improving health throughout the world! :) After your video yesterday, I became intrigued (as usual) and searched for information about IGF-1 and became a bit confused.
    First, I watched a BBC documentary in which the presenter, on the advice of a couple of researchers and physicians, went on a 4-day fast and then occasionally fasted for a couple of days at a time. This seemed to be enough to significantly lower his IGF-1 levels with no apparent change in his Western-based diet otherwise. He lost a bit of weight. So do you think the drop in IGF-1 levels while on a healthy entirely vegetable-based diet has to do with the vegetables themselves or do you think it could have more to do with a lower calorie intake or drop to a normal weight?
    Second, in a video on YouTube, Dr. McDougall accused soy protein of being even worse than milk and animal protein in boosting IGF-1 levels. However, in the same video, he also says that the amount of IGF-1 in vegan men and women is much lower, even though they eat lots of soy. We’re a vegan family that consumes lots of soy products, so if IGF-1 levels are the key to good health, should we also be aiming for lesser calories and less soy, at least in the adults?

    • Thea

       matchalover: Great questions.

      I am not an expert and can not answer all of your questions.  However, I thought you might be interested to know that the Portland VegFest conference this last weekend featured speaker, Mark Messina, PhD.  “Dr. Messina has devoted his time primarily to the study of the health effects of soy foods and soybean isoflavones.”

      After looking at all the science around soy, his bottom line was that people *should* be eating soy foods.  There were some limitations.  For example, Dr. Messina did point out the same case study that Dr. Greger points out where a man drinking huge amounts (12 cups?) of soy milk every day ran into problems.  But he felt that all the research points to an over all health benefit from a certain number of servings of traditional soy foods (like tofu and tempeh) each day.

      I only caught the last part of the speech.  So, I don’t know if he addressed IFG-1 specfically, but I did catch his bottom line and I do know that he *did* address cancer.

      That said, I do know that Dr. Greger has videos coming up with titles such as:   “Too much soy may neutralize benefits” and “How much soy is too much?”  So stay tuned.  Based on all of the videos from Dr. Greger and based on the talk by Dr. Messina, it is my guess that like many things (such as protein, vitamin A, etc.), there is an optimal range for soy food intake.  You don’t want too little or too much.

      • Thea

         I will also add that I found this quote about Dr. Messina: “He is a former program director with the National Cancer Institute
        (NCI), where he initiated a research program on the anticancer effects
        of soy.”

      • Joyce Champion

        Dr. McDougall has pointed out that traditional soy foods such as tofu are good. Overly processed soy foods such as the fake meats and cheeses are bad.

    • Doug R

       Apparently, eating less food includes eating less of the bad food that increases IGF-1 in our bodies. I don’t think it’s a matter of a vegan vs. an omnivore diet, but a matter of the specific nutrients in a food, vegan or animal. Seems to me that we’re better off eating most plant foods since this is what nature suggests. Our ancestors weren’t fast enough to run down animals, didn’t have claws and fangs, so they naturally ate plants. But when their ideal foods were in short supply or they were less in tune to their instincts, they became scavengers and ate whatever was available. It’s possible however that not all plant foods were part of our original diet or are healthy for us- especially processed, concentrated soy, as Dr. McDougall gives evidence for in so it’s probably best to avoid it as a staple. Legumes, along with grains and some other plant foods have anti-nutrients and poisons in them, although some of them can be removed by cooking. But not all of them. And I don’t know whether the first humans cooked or not. So it’s possible that not all of grains or legumes are totally healthy even after this processing or part of our native diet. All I can conclude is that just because it comes from a plant, that doesn’t mean that we should eat it. I would guess that most traditional vegetables and fruits are safe though- although I wonder about the nightshade family of vegetables for example, are safe at least some people who seem to be sensitive. And there is evidence that cultures have thrived on white rice for example, the bran containing some toxins.

    • SJS

      Dr. Luigi Fontana has studied calorie restrictors and found that they had higher IGF-1 levels than raw food vegans.  Looking more closely, it was found that the CR guys were eating 25% protein, while RFV were eating 10-12% protein.  When the CR guys lowered their protein intakes to 10%, their IGF-1 came down.  PMID: 18843793

      Even elevated levels of vegetable protein (ie soy isolates) can lead to increased
      IGF-1.  PMID: 7571965 .  

      I would venture to guess that brown rice protein, Hemp protein and split pea 
      protein would elevate IGF-1 if consumed in excess.   
      This is something that bodybuilders (even the vegan ones) have known
      for some time.. 

    •  Hi,

      I also watched that BBC documenatry, and I would love to know the answer to that as well. The documentary is: BBC Horizon 2012: Eat, Fast and Live Longer.

    • InterestedParty

       I too saw the Horizon show on fasting and IGF-1.  I am really curious to know  how fasting might fit into an overall healthy vegetarian/vegan diet, as “matchalover” asked.

  • Traxmom

    Hoping you’ll get into the details of which foods are high in IGF-1. For instance, dairy for sure, but what about soy protein isolate, as Dr. McDougall discussed in one of his videos online. Soy protein isolate qualifies as “plant-based” and yet it seemed to elevate IGF-1 levels even more than dairy, according to McDougall.

    • Doug R

       Here’s the study Dr. Mcdougall cites:

    • kerin gordon

      Soy has natural estrogen soy eating soy with breast cancer will increase the cancer…..its a fact cuz when I took care of cancer patients they gave me their soy if they had any…plus my dad died of breast cancer and he couldnt eat any tofu, not that he was a big fan….and my mom has breast cancer but she is big on organics and veggies…and my sister had it twice…actually the obituary said he died of breast cancer…which did spread to his liver….but he died from the hospital…he got pneumonia and twice they put his leg blow up cuffs…..i dont know what you call them…way to tight and he couldnt walk….the second time he never could walk again….they day he was due to leave…he died….the veggie diet gave him two years….after he was on hospice….and off hospice and driving and painting and dancing.

      • Morgan

        The fear over soy, and the reasons for it, are unjustified. Soy does not have natural estrogen. Please do more research.

  • Christopher Wark

    Fantastic. Thanks for sharing Dr. Greger!

    I used a raw vegan diet to beat stage 3 colon cancer without chemo back in 2004.
    I was 26.

    It’s interesting that while that diet works for some, it does not work for all. I’ve also met people who have used a raw meat and/or ketogenic diet to reverse their cancer which is high in IGF-1…

    Any thoughts on that approach?


    p.s. my story is at

  • R Ian Flett

     QUOTE….Int J Endocrinology .2010 Sep 22.
    aerobic training decreased the circulating levels of IGF-I by 9%, while IGFBP-1
    levels increased by 16%. An interesting finding was that higher pre-training
    level of IGF-I was associated with greater decline in IGF-I with training.
    Insulin-sensitizing low-intensity aerobic exercise is thus considered to be an
    effective method for downregulating IGF-I and upregulating IGFBP-1 levels: 

    And the very latest,  from Clin
    Endocrinol (Oxf). 2012 Sep 25. Concludes:

    Older men with higher IGFBP1 level, or both lower IGF-I and
    testosterone, are more likely to be frail, while those with lower IGF-I and
    higher IGFBP1 are more likely to become frail. Components of the IGF-I system
    may be biomarkers or independent predictors of frailty.

    So if we eat more plants and do more walking, we reduce our
    cancer risk and die of frailty instead.

    Longevity is clearly not just a case of endlessly reducing/increasing some serum-level  components
    such as IGF-1, testosterone, vitamin D, selenium, zinc, or anything else, but
    finding what the optimum levels are and what baseline we are starting from
    (e.g., the appalling Western processed diet). What makes it so maddeningly complex is
    that these optimal levels are interactive, and that’s before genetics and
    epigenetics are factored in.

    IGF-1 protects the skeleton, but at what level does it
    become a negative and in what context? Also IGF-1 repairs muscle tissue in
    bodybuilding’s high resistance exercise, but it seems to do this locally. Does
    this have adverse effects elsewhere or are the local effects confined? So much
    more research needs to be done as paradoxes abound.

    • daisy

      so is low intensity exercise (walking) better than higher intensity exercise(running) for cancer prevention?is 30 minutes better than 60 minutes daily?

      • R Ian Flett

        A very tough question. Recent studies in the UK show that major CVD benefits for most genetic types could be achieved through only ONE minute of intense cycling (to exhaustion) three days a week, but there is no indication of what this does for cancer. Interval training loses weight faster than steady walking, but it probably increases IGF-1 levels. Intense exercise triggers repair mechanisms, but at what cancer cost?
        If you look at centenarians, most were active in the sense of lots of walking, or time on their feet, but were not athletes, bodybuilders, or heavy exercise junkies.The assumed trade-off between reproductive energy expenditure and longevity, if true, may have a part to play here. Building larger muscles such as heart muscles via heavy exercise may also increase the (growth) hormone components of cancers. I wish I knew.

    • Doug R

       Distance runners are notoriously skinny while sprinters are well-muscled. The distance runners probably have too little IGF-1 and are frail, while the sprinters probably have a healthier level and maintain their muscle mass. Sarcopenia (loss of muscle) with age is one of the things we need to be concerned about as we get older, so I’ve started doing uphill sprints and taking branched chain amino acids, which the research seems to support as effective measures against it. So, you see, R Ian Flett, you don’t have to die of either frailty or cancer. Check out High Intensity Interval Training and BCAA articles on the internet.

    • Mike Quinoa

      Vegans have as much free testosterone as meat-eaters, so that would not be an issue. Exercise and a bit of weight-lifting should take care of any fraility issues. Still a good idea to have higher levels of IGFBP1:

  • Zoomletta

    I was eating a plant based diet when I was diagnosed with breast cancer.

    • JHoff

      I wouldn’t rule out exposure to plastics/toxic chemicals as a cause then. Technically, I think you should have lower risk on a strictly plant-based diet but frequently our foods are wrapped/shipped in plastics that have estrogen-like chemicals. Also, do you eat/drink things off a plastic or heat them up in the microwave, etc. ? Just a thought to consider. Hope you get well soon!

  • Hathor42

    The three studies involved low fat, high fiber, not just plants.  (Actually, looks like Barnard allowed a little meat.)  Low fat was defined as 15% or less.  If you’re going to talk about a “healthy plant-based diet” as shown in particular studies, you should specify the diet in question.

    The McCarthy article makes specific points about low fat vegan diets, not only vegan diets in general.

    Pritikin himself specified 10% fat.

    I’ve been watching your videos from the first one on.  Lots of great stuff.  But I haven’t heard you specify your notion of a healthy fat level or if you think that one exists.

    If you don’t, then I don’t think it fair to rely on Pritikin, Ornish, Esselstyn, Barnard, and others whose diets do limit fat.

  • Liz

    …But didn’t Pritikin DIE of Cancer while eating an impeccable plant-based diet?

    • Toxins

      not sure how accurate this information is but “In the early 1980s, he began to suffer severe pain and complications related to his decades-long fight with leukemia, which had been in remission for 27 years.[4][5] He committed suicide on February 21, 1985.[6]”

  • Liz

    Dr. Grerer, Didn’t Pritikin GET cancer, and was dying from it? Haven’t studies comparing vegetarians vs. non-vegetarians always concluded pretty much same all cause mortality? Only significant protection I’ve noticed is from ischemic heart disease. The vegetarians died of cancer.. just like the meat eaters, and had higher probability of getting certain cancers? Why doesnt this match up with what you are saying or Furhman or Mcdoughall? Am I restricting what I eat unnecessarily? Pointlessly?

    • Thea

      Liz: While you can find studies to show anything you want, the way to get your answers is to look at the body of scientific evidence. That body of evidence is pretty clear, with studies favoring plant based diets FAR outweighing studies saying anything else.

      Concerning your specific questions: “Haven’t studies comparing vegetarians vs. non-vegetarians always concluded pretty much same all cause mortality” No. I’ve seen studies where vegetarians and vegans live longer. The latest study I saw put vegetarians at 7 years longer life. Based on what we know about nutritional science, I would expect whole-food vegans with b12 supplement to live even longer – precisely because we get less cancer, heart disease, etc.

      “The vegetarians died of cancer.. just like the meat eaters, and had higher probability of getting certain cancers?”
      No. Not just like. One thing to remember is that there can be a huge difference between vegetarian and vegan. Vegetarians can end up getting as much animal protein as meat-eaters. Dr. Greger recommends eliminating animal products, not just meat. So, it probably isn’t hard to find studies that show small effects on vegetarians. However, vegans have been shown to have signficantly less cancer, especially breast, prostate, colorectal and I believe others. I highly recommend that you read The China Study if you want to educate yourself on the link between diet and cancer. You might also watch Dr. Greger’s video Uprooting the Leading Causes of Death – available on this site.

      re: “The vegetarians died of cancer…”
      One thing I like to remind people is that lowering probability of something happening is not the same thing as guaranteeing that it won’t happen. If I find out that I lower my risk of getting cancer by say (I’m just throwing out a number to make a point) 50%, I consider that a significant reduction and worth my effort. Put another way: If two people in your family would get cancer by doing nothing, but one person could be saved by doing something, wouldn’t it be worth it to do something?

      So, what is the actual probability/lessening of risk? That depends on types of cancers, environmental factors, which studies you look at, etc. But one think is almost always clear: The lessening of risk is significant. So, to answer your question: “Am I restricting what I eat unnecessarily?” That’s for you to answer. But if you want the best chance of avoiding the most common diseases afflicting Americans and other Western cultures, then the answer is very clear: NO. You are doing exactly what you need to do to help yourself.

      Best of luck to you.

      • Pedro

        Researchers studying people over 100 years old around the world reported that all of them ate meat, none ate yoghurt, and none exercised for their health. They had nothing else in common, including their diets.

    • Vic

      Pritikin DID NOT die of cancer. In 1985, he took his own life. But..his diet gave him 27 years extra life compared to the time he was told he had. Back in the 50’s he had a “decades-long fight with leukemia, which had been in remission for 27 years.[4][5] (thanks to his diet) He committed suicide on February 21, 1985.[6]

  • Morgan Miller

    Vegan propaganda at its best. There are plenty of other possible reasons for early puberty. We have been eating meat and other sources of animal protein for thousands of years. Just now these proteins are causing early puberty? This is a disgrace. I can’t believe people buy into this utter crap because they are sooooo biased by their belief thst we should not kill animals for food. This is very sad. Please, please, come up with better reasons to eliminate all animal products from our diet! The China Study and Forks Over Knives have both been debunked by some very intelligent people who did very solid research. You can’t use these weak arguments anymore.

    • Marcella

      Morgan, just because you think this way doesn’t mean anything, have you got actual scientific data to support your loathing of a nutritional diet? Your statement sounds like you’re the hefty wife of a beef farmer sitting around a table knitting with your friends, no data, just unsupported greasy hate statements

    • Jhoff

      FYI, for the “thousands of years” we haven’t been injecting our meats and diary with hormones. If you don’t believe “vegan propaganda” then it is YOUR loss. I feel for your family that will have to mourn your early departure from this Earth. Your choice entirely. No one is out there taking away the steak you are eating against your will!

    • Wade Patton

      Try it. You obviously never have.

    • Melissa

      Modern intensive farming has brought down the cost of meat, so the average ‘meat eater’ today is having much more meat than in the past, so there is a quantity effect to drive up IGF-1. Also the animals are now grain fed, not pasture fed, which makes a big difference to the meat’s lipid profile.
      However I’m sure that other major changes such as more sugar, less ‘incidental’ exercise (eg more walking, as opposed to more organised sport, in the past) also affect IGF-1 and other hormones in our children.
      Another changes is that chicken used to be very expensive, with factory farming it is very cheap, Chicken was particularly statistically associated with early puberty in the studies on diet associations. Chicken twice a day was never normal for our ancestors!

  • Alessandro

    Just for prevision, the published research does not say that the diet was vegetarian; indeed the “diet consisted of natural whole grains, fruits and vegetables with limited amounts (< 3.5 oz) of fish, fowl or lean meat and nonfat milk".

  • This is friggin incredible!

  • Charzie

    Chris, I am familiar with your story from watching Quest for the Cures, a fantastic and illuminating series, and kudos to you for being so brave and for sharing your experience with so many! (Gotta love the internet or we probably wouldn’t know about any of it!)
    Anyway, I am also very interested in the huge issue of the diverse dietary approaches, and wish someone could reply to your query! I know this is an older post, but the question still begs some feedback. I’m aware no one has all the answers, but it would be great to at least hear some thoughts on the matter! Anyone?

  • Linda N

    No where in this video does it let anyone know that Pritikin committed suicide after suffering severe pain and complication due to his having leukemia.,,20090134,00.html

    Of course chemo is never the answer to a cancer diagnosis, anyway, the way I see it.

    • Wade Patton

      I don’t understand how his ultimate demise is relevant to the work and example he set. The autopsy of his body found a remarkably healthy (for the Western world) vascular system. And as any suicide, no one other than the subject can fully know his/her circumstances that led to that final breaking point. We can only guess and imagine. Our conjectures mean nothing.

      An associate of mine recently attempted such. I’ll never know exactly, and won’t ask, it changes nothing between us. I only wish him full recovery and more peace of mind and body for the rest of his duration.

    • William Dwyer

      What you fail to mention is that following the adoption of his diet,, Pritikin’s leukemia went into remission for 27 years. Sadly, due perhaps to advancing age, his leukemia relapsed in the early 1980’s, which led to his committing suicide in 1985 at the age of 69.