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The Answer to the Pritikin Puzzle

Lower cancer rates among those eating a plant-based diet may be a result of reduced blood levels of IGF-1 and enhanced production of IGF-1 binding protein.

September 27, 2012 |
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Remember the Pritikin experiments? You put people on a plant-based diet and exercise and in as little as 12 days you can turn their bloodstream into a cancer cell fighting machine. Here's the before picture, a layer of breast cancer cells is laid downin a petri dish and then blood from women eating the standard American diet is dripped on them, and as you can see, even people eating crappy diets have some ability to break down cancer. But after just 12 days eating healthy, blood was drawn from those same women, dripped on another carpet of breast cancer cells and this is what you're left with. Their bodies cleaned up!

You can also look at it another way. This is what's called terminal-deoxynucleotidyl-transferase-dUTP-nick-end-labeling or "tunel" imaging, which measures DNA fragmentation, cell death. Dying cells show up as white spots. So again, this is the before, what the blood of your average woman can do to breast cancer cells. If can kill of a few. But then after 12 days of healthy plant-based living their blood can do this.

This is called programmed cancer cell death. After eating healthy, their own bodies were able to reprogram the cancer cells—forcing them into early retirement. It’s like you’re an entirely different person inside. How does a simple dietary change make one’s bloodstream so inhospitable to cancer in just a matter of days? That, was the next question they set out to answer, and they finally did, in 2011... “Here we sought to determine the underlying mechanisms for these anticancer effects.” And what they came up with was IGF-1.

If you measure the blood levels of Insulin Like Growth Factor One before and after 11 days on a plant-based diet with exercise, IGF-1 levels significantly drop. And, IGF-1 binding protein levels, significantly rise. That’s one way our body tries to protect itself from cancer—from excessive growth—by releasing a binding protein into our bloodstream to tie up IGF-1. It's like our body’s emergency brake. Yeah sure, in as little as 11 days a healthy diet can reprogram your body to slow down IGF-1 production, but you still have all that IGF-1 circulating in your bloodstream from the bacon and eggs you had the week before. So your liver releases a snatch squad of binding proteins to take it out of circulation pronto. Exercise alone can drop IGF-1 levels, but you need the plant based diet to get those kind of snatch squad levels.

And so with that combination, 20% less IGF-1, and 50% more IGF binding protein, no wonder there was such a dramatic cancer cell die-off after just a few days.

So did they solve the riddle, did they figure out how a plant-based diet shuts down cancer growth? Well the definitive study wasn’t published until recently.

Same as last time; before and after a few weeks of a plant-based diet. Cancer cell growth drops; programmed cancer cell death, shoots up. But then here’s the kicker. Remember how IGF1 levels dropped? Well, what if you add that exact same amount of IGF1 back in with the cancer? … It erases the diet and exercise effect. It’s like you never started eating healthy at all. Now if cancer growth just came back down to here you’d think OK, IGF was part of it, but the fact that it eliminated the effects of the lifestyle changes, suggests that that was the mechanism all along: Walking, and eating a plant based diet for just a few days, lowers circulating IGF1 levels, which then can reverse cancer growth.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by Kerry Skinner.

To help out on the site please email volunteer@nutritionfacts.org

Dr. Michael Greger
  • http://nutritionfacts.org/ Michael Greger M.D.

    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.

    If you haven’t yet, you can subscribe to my videos for free by clicking here.

    • 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

    Amazing!

    • http://nutritionfacts.org/ Michael Greger M.D.

       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?

  • http://www.facebook.com/profile.php?id=670735069 Tan Truong

    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.”

    • 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  http://www.youtube.com/watch?v=mHYFOJBU434 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.. 

    • http://twitter.com/mundaysa Pilar Munday

       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:

      http://www.ncbi.nlm.nih.gov/pubmed/12629084

    • 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.

  • R Ian Flett

     QUOTE….Int J Endocrinology .2010 Sep 22.
    ..low-intensity
    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:

      http://www.ncbi.nlm.nih.gov/pubmed/22357965

  • Zoomletta

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

  • 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]” http://en.wikipedia.org/wiki/Nathan_Pritikin

  • 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.

  • 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

  • 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".

  • http://www.naturallifeenergy.com/ Aqiyl Aniys

    This is friggin incredible!