Doctor's Note

To review, I started out introducing Nathan Pritikin (Engineering a Cure), and the elegant series of experiments that became part of his legacy (Ex Vivo Cancer Proliferation Bioassay). They were able to demonstrate the means by which a plant-based diet and exercise could suppress the growth of breast and prostate cancer cells (see The Answer to the Pritikin Puzzle), and protect against prostate enlargement (see Prostate vs. a Plant-Based Diet). For more on BPH, see Some Prostates Are Larger than Others. I also asked, and answered Is It the Diet, the Exercise, or Both? We learned in IGF-1 as One-Stop Cancer Shop that the cancer-promoting growth hormone IGF-1 seemed to be The Answer to the Pritikin Puzzle—but why? What is it about plant-based diets that lower IGF-1 levels, and increase our body’s ability to neutralize IGF-1? Find out in Protein Intake and IGF-1 Production.

For further context, be sure to check out my associated blog posts: Vegan Men: More Testosterone But Less Cancer, and Animal Protein and the Cancer Promoter IGF-1.

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  • To review, I started out introducing Nathan Pritikin (Engineering a Cure) and the elegant series of experiments that became part of his legacy (Developing an Ex Vivo Cancer Proliferation Bioassay). They were able to demonstrate the mechanism by which a plant-based diet and exercise could suppress the growth of breast and prostate cancer cells and protect against prostate enlargement (more on BPH here, and <a href="Prostate Versus a Plant-Based Diet“>specific foods that may help). I also asked and answered <a href="Is It the Diet, the Exercise, or Both?“>Is It the Diet, the Exercise, or Both? We learned that the cancer promoting growth hormone IGF-1 seemed to be The Answer to the Pritikin Puzzle, but why? What is it about plant-based diets that lower IGF-1 levels and increase our body’s ability to neutralize IGF-1? Find out in Monday’s video-of-the-day Protein Intake and IGF-1 Production.

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

    • Coacervate

      I have a friend who is fighting a bad cancer.  Is there any way we can get her injections of this binding protein?  I should have asked if it is a good idea first of all.  Is it?  Would it work on post metastatic (if i’m saying that right – it has gone to other locations now).  I hope you can answer.

      • Joe Nunes


    • Fabien Coquel

      Thanks for your videos, great work !

      I have read that Capsaicin and soy protein could also raise IGF-1 levels in our bodies
      (maybe only processed soy or isolated soy protein for the soy part).

      Could you check the latest studies on theses and enlighten us about what is healthy and in which quantities ?

      • Doug R

         Thanks Fabien for looking up these studies for us. The second one is particularly . It says that the sea weed, Alaria esculenta, downgraded the IGF-1 producing effect of soy. This could be why Asians can get away with eating soy and have such a low rate of cancers- because they also eat sea vegetables which may counter soy’s negative effect.  Hopefully, other kinds of sea vegetables besides Alaria esculenta, that is: dabberlocks or badderlocks, or winged kelp  from the North Atlantic work as well or better. 

      • I found the middle link there very interesting. I’ve just ordered some wakabe and Welsh laver bread to add to my diet. Hopefully that will mitiagte somewhat, any increase in IGF-1 due to my soya milk consumption.

        • rotorhead1871

          use almond milk, go slow on the soy

      • April Lillie

        I found your links interesting. They all talked about isolated soy compounds though, isovlavones in the first study and isolated soy protein in the second. This may not be different from isolating beta carotene and giving it in a vitamin pill only to find out it increased risk of lung cancer. We didn’t stop eating carrots after that study!

        I was concerned about the soy issue, but like everything else, if eaten as a whole food, minimally processed such soy milk, tofu, tempeh and miso, I think itvhasctrenendous benefits. Soy protein burgers, bacon and other highly processed foods are just that. Highly processed junk. Stay with a whole foods plant based diet and the benefits are great, even with the inclusion of the soy bean. It’s a bean.

      • Nouh

        I’ve watched a presentation on youtube by Dr. Mcdougalle about the death of Steve Jobs in which he adviced againt fake meats and isolated soy proteins. So, I guess one should avoid all proccessed things and eat beans and whole plants unproccessed.

        • rotorhead1871

          agree …go with the beans/ veggies….if you must …go slow on the soy……soy isolates are not good overall

      • Toxins

         Soy Protein Isolate does in deed IGF-1 more significantly than cows milk.

    • DT


      The differences found between the IGF1 level of vegan and non-vegan are small – only 8% difference (in males).
      This difference translate to very little risk reduction for cancer. For example, according to this study , 8% lower IGF1 is only 3% less chance of prostate cancer (*if* the association between IGF1 and prostate cancer is indeed casual).

      Also, as I noted in other videos, the Pritikin diet which is mentioned in the beginning of the video is not vegan or even vegetarian.

      • Thea

         DT: 3% less prostate cancer is quite significant in my opinion when you think about the numbers of people who currently get the cancer.

        • DT

          According to prospective cohort studies, consumption of dairy is associated with LOWER rates of colorectal cancer, breast cancer, and cardiovascular diseases, so the benefits of dairy consumption may cancel the risks.

          • Thea

            Interesting.  A conclusion that dairy has overall benefits of any kind is the complete opposite of the studies I am aware of.  Plus it doesn’t make sense.  If it makes sense to you, go for it.

            I wonder who funded those studies…?  Just a thought. 

          • DT

             Most epidemiological studies are not funded by the industry.

          • HemoDynamic, M.D.


              Are you cherry-picking?

          • DT

             I never tried to count the number of industry funded   epidemiological studies. If this interest you, you can count how many of the 18 studies appearing in the meta-analysis below were industry funded.


          • HemoDynamic, M.D.

            There are absolutely no benefits to drinking or eating another mammals mammary gland excretions. 

            Especially when one 16oz glass of it is loaded with 360,000,000 pus cells (dead white blood cells) and over 1,000,000 bacteria. That is what is allowed by law:

            Also you allow your body a host of exposures to bugs like Mycobacterium Avium Parataburculosis and this wonderful list from Cornell University;

            Nothing like a nice tall glass of sterile pus and bacteria.  YUM! 

            A great read is Joe Keon’s book WhiteWash. A sample preview link is provided.

            Also John Robbins (son of Baskin & Robbins Ice Cream legend) has a great read as well, “No Happy Cows”

            Drinking milk is almost like signing the old song, “DDT is Good for You and Me!”

          • HemoDynamic, M.D.

            The Cartoon reference from above.  See image.

          • DT

             The books you cite are not credible sources.

          • HemoDynamic, M.D.

            I wouldn’t normally reply or waste my time with such an ignorant reply.  But in defense of the people who spend countless hours, days, weeks, years and lives dedicated to credible research I must speak up.

            “Not credible sources” you say.  Their sources are from journals such as JAMA, New England Journal of Medicine, American Journal of Clinical Nutrition, British Medical Journal, Lancet, Annals of Internal Medicine, American Journal of Epidemiology etc.

            In Whitewash there are nearly 1000 references supporting the evidence that milk is crap, Literally and anecdotally.

            Quotes in Whitewash:

            Nathan Pritikin: “The most damaging foods are dairy product.”

            John McDougall, MD: “There is one thing dairy products have more than any other food I can think of: contamination.

            T. Colin Campbell, PhD: “Dairy has been considered a health food, and that’s an unfortunate myth.”

            Benjamin Spock, MD: “Cow’s milk in the past has always been oversold as the perfect food, but we are now seeing that it isn’t the perfect food at all and the government really shouldn’t be behind any efforts to promote it as such.”

            Walter Willett, MD, MPH, DrPH: “Dairy products shouldn’t occupy a prominent place in our diet, nor should they be the centerpiece of the national strategy to prevent osteoporosis.”

            Oh and Joseph Keon, PhD has his doctorate in Nutrition.

            Here is a quote by Neal Barnard, MD as you know one of great leaders in the medical nutrition arena:
            “Most of us grew up with the idea that mild is healthful, if not essential. And Yet research has shown a surprisingly different side to dairy products, linking it to a broad range of serious health problems.  Whitewash takes a comprehensive look at the problems associated with drinking milk and the industry that promotes it.  This book has the potential to dramatically change your health.”

            Regarding No Happy Cows I will leave that research up to you to discover but here is a wonderful forward from T. Colin Campbell, PhD:
            “John Robbins connects the dots that need connecting–environmental, personal health, societal economics, and personal meaning. Scientific researchers also would do well to read what Robbins says.”

            I’m not sure what you think is credible but these sources surely are, and have the information to change the world for the better.  I hope everyone takes the time to read these books and dispell the myths and hype that commenters such as yourself perpetuate.

          • DT

            1. While Whitewash have references to paper in scientific journals, these papers were probably cherry-picked. The book has not gone through peer review, which makes it a non credible source.

            2. If Nathan Pritikin thought that dairy is damaging, why does his diet includes two servings of dairy per day?

          • HemoDynamic, M.D.

            Your definition of ‘credible’ is your own so I do not understand why you waste your time commenting on a “non-credible” site such as 

            Please, for your own sake, keep drinking milk.  It obviously serves you well.

            “All truth goes through three stages.
            First it is ridiculed.
            Then it is violently opposed.
            Finally, it is accepted as self-evident”
            Arthur Schoepenhauer, German philosopher

          • I don’t suppose you cherry pick studies at all.

          •  Thank you. Much appreciated.

          •  Thanks for the points!

          • Toxins

            A review published in the Journal of Pediatrics focused on the benefits of dairy “the findings of epidemiologic and prospective studies have raised questions about the efficacy of the use of dairy products for the promotion of bone health. ” after a review of the existing literature and finding “A positive relationship between dairy product consumption and measures of bone health in children or young adults was reported in 1 of 4 cross-sectional studies; in 0 of 3 retrospective studies; in 0 of 1 prospective study; and in 2 of 3 randomized, controlled trials. Only 1 of these randomized clinical trials adequately controlled for vitamin D intake, and it showed no significant effect of dairy products on BMD [bone mineral density]” , they concluded, “Scant evidence supports nutrition guidelines focused specifically on increasing milk or other dairy product intake for promoting child and adolescent bone mineralization.”

            A meta-analysis published in the British Medical Journal found, “The small effect of calcium supplementation on bone mineral density in the upper limb is unlikely to reduce the risk of fracture, either in childhood or later life, to a degree of major public health importance.”and “The authors concluded that the literature did not support recommendations for consumption of dairy products for bone health end points in children and young adults…Our quantitative systematic review confirms this conclusion” The authors also state, “Our results also do not support the premise that any type of calcium supplementation is more effective than another.” Even studies that used intakes of 1400 mg per day of calcium showed no benefit.

            An editorial accompanying this meta-analysis pointed out, “Populations that consume the most cow’s milk and other dairy products have among the highest rates of osteoporosis and hip fracture in later life. Given this fact, it is important to ask whether sufficient evidence exists to continue assuming that consumption of these foods is part of the solution.” They concluded “It is time to revise our calcium recommendations for young people and change our assumptions about the role of calcium, milk, and other dairy products in the bone health of children and adolescents. While the policy experts work on revising recommendations, doctors and other health professionals should encourage children to spend time in active play or sports, and to consume a nutritious diet built from whole foods from plant sources to achieve and maintain a healthy weight and provide an environment conducive to building strong bones.”

            A review published in the American Journal of Clinical Nutrition of the research on the effects of dairy products on bone health found 57 studies, and of these, 21 studies were considered to have stronger-evidence, worthy of inclusion in this review. “Of 21 stronger-evidence studies, 57% were not significant, 29% were favorable, and 14% were unfavorable.” Keep in mind that the majority of these studies were funded by the dairy industry, and even with this natural bias and influence to produce positive outcomes, no better than 29% of the studies were favorable to bone health. One of the studies that showed unfavorable results that was funded by the dairy industry showed some shocking outcomes. The findings showed post menopause subjects who received the extra milk (three 8 ounce glasses of skimmed milk daily) for a year lost more bone than those who didn’t drink the extra milk. The authors wrote, “The protein content of the milk supplement may have a negative effect on calcium balance, possibly through an increase in kidney losses of calcium or through a direct effect on bone resorption…this may have been due to the average 30 percent increase in protein intake during milk supplementation.” Skim milk is very high in protein so this is unavoidable unless one is to consume the very fatty whole milk in which 2-5% of the fat content is trans fat and is very high in saturated fat.

            Its evidence such as this that I am unconvinced calcium should be from cows milk. Long term studies on vegan bone density comparing the omnivores diet showed the same bone density “…although vegans have much lower intakes of dietary calcium and protein than omnivores, veganism does not have an adverse effect on bone mineral density and does not alter body composition.” The vegan participants had been on a vegan diet an average of 33 years.

            I find it interesting that modern society believes that the human species is dependent on the milk of another animal species. The primary biologic purpose of cow’s milk is to grow a 60 pound calf to a 600 pound cow in less than 8 months. This is no way natural to humans as cow’s milk has high concentrations of protein, potassium, sodium, calcium, and other nutrients to sustain rapid growth. In comparison, these nutrients are at a three to four times lower concentration in human milk than cow’s milk. Milk is used to promote growth, so how is this natural as human adults to be consuming milk, let alone another species of animals milk? Dairy is a heavy promoter of insulin like growth factor in adults. This spike in IGF-1 is the most likely source of positive bone growth in the studies showing favorable outcomes of dairy on bones, not necessarily the calcium. Elevated IGF-1 does more harm than good in adults, it heavily promotes tumor growth in breast, prostate, lung, and colon cells and accelerates the aging process.

            The consumption of dairy in children has resulted in earlier puberty. “The effect of animal protein intake, which was associated with an earlier puberty onset, might mainly be due to dairy. “An earlier puberty onset has been related to an increased risk for hormone-related cancers in adulthood. For example, a meta-analysis of 26 epidemiological studies reported a 9% risk reduction for breast cancer with every additional year at menarche. Additionally, recent study results demonstrated that a 1-y delay in menarche was associated with a 2.4 to 4.5% lower total mortality.

            The concern with dairy and hormone dependent cancer is something to think about as well. It has been shown that consuming dairy significantly increases circulating steroid hormones in woman and that vegetarians have far less of this hormone. “In conclusion, greater consumption of red meat and dairy products might influence circulating concentrations of SHBG and estradiol, respectively. Given the well-established role of steroid hormones in breast cancer etiology for postmenopausal women, these findings may have important health implications” Tumor growth from these hormone imbalances is also evident “A dramatic increase in estrogen-dependent malignant diseases, such as ovarian, corpus uteri, breast, testicular and prostate cancers has been recognized. Ganmaa et al. investigated the incidence and mortality of testicular and prostate cancers in relation to dietary practices. Among various food items, cow’s milk and cheese had the highest correlation with incidence and mortality rate of these cancers” Children are at high risk “Among the exposure of humans, especially prepubertal children, to exogenous estrogens, we are particularly concerned with” These xenoestrogens from lactating preganant cattle (the majority of commercial cattle used for milk) significantly raised estrogen levels in male adults and reduced testosterone levels and did even more so in children. This is significant since these estrogens have mutagenic affects “Toxicological and epidemiological studies have indicated that E2 could be categorized as a carcinogen. Milk is considered to be a rich source of estrogens. Indeed, E2 concentration is higher in mammary drainage than in the peripheral circulation in high yielding cows.”

          • Thanks for the info. I told a vegetarian that cow’s milk is nasty. She didn’t want to hear it, and said “Oh you’re vegan”. I said something like, “It has nothing to do with being vegan; it’s nasty no matter what diet we’re on.”

          • Toxins

             DT, what your claiming is complete nonsense.

          • Could somebody on your staff please clarify this? If I recall correctly, the WCRF/AICR meta-analysis ( does conclude that dairy is associated with lower risk of colorectal cancer, but also says dairy is associated with higher risk of prostate cancer (perhaps due to high calcium) and in their latest update, says it’s not clear as to association with breast cancer risk. I also recall a discussion somewhere in that report of the galactose in dairy and the possibility of it increasing ovarian cancer risk. Could your staff please have a look and inform us?

      • Thinkabouddit

        This video said at .30 that “people eating plant-based diets for 14 years had half the IGFl-1 in their bodies {}.” That’s 50% less, not 8%.

        • R Ian Flett

          Br J Cancer. 2000 Jul;83(1):95-7.
          Mean serum insulin-like growth factor-I was 9% lower in 233 vegan men than in 226 meat-eaters and 237 vegetarians (P = 0.002). Vegans had higher testosterone levels than vegetarians and meat-eaters, but this was offset by higher sex hormone binding globulin, and there were no differences between diet groups in free testosterone, androstanediol glucuronide or luteinizing hormone.

          As is common here some careful cherry-pickin’ going on here.

          • Maledictis

            9% less IGF-1 is ALL GROUPS taken into account. 50% less is ONLY the 14 years vegan group.

          • Daniel

            You can be vegan for a month and participate in a study; long term vegans have a 50% lower levels of IGF1! These results are astonishing, nothing less. Most meat would have to fast 3-4 for days a week to achieve anything similar.     

          • DT

             You and Meledictis are confusing the studies.

            The study that compared vegan with non-vegan is Allen et al 2000. In this study, the average IGF1 level were 18.5 in vegans vs. 20.1 in meat eaters. This is a small difference.

            The other study is Ngo et al 2002. In this study, people on the Pritikin diet+exercise reduced their IGF1 levels by 55% (compared to their own levels) in 14 years. However, the Pritikin diet is NOT vegan! (and not even vegetarian).

      • JeffW

        One of the problems with this study between IGF-1 and prostate cancer is that it’s a case-control study. In this kind of study, the researchers go through medical records or use some other kind of survey to find say, prostate cancer cases and then they look at their IGF-1 levels, which are of course high. Then they find a bunch of supposedly healthy subjects who don’t have cancer (that is, not yet) to use as controls and they check their IGF-1 levels too, to see if there are any differences in their IGF-1. And what do they find? Only very slight differences. Why? Because the whole population except for the 2% who are vegan, are on the Standard American Diet and eat excessive animal protein, which increases their IGF-1 and their risk of cancer. Not everyone with high IGF-1 gets cancer or gets it right away, but close to half of the population will at some point in their life have to cope with cancer- unless they shrink their odds nearly to the vanishing point by going vegan. That’s why those who have cancer now have comparable levels of IGF-1 to those who don’t- because they’re all in the same S.A.D. high animal protein boat and eventually, a good number of them are likely to get cancer- and probably diabetes, heart disease and a whole lot of other aliments. Want that? Not me! I’m definitely staying vegan.

        • DT

          1. The study I cited was a prospective case-control, meaning that the blood sample were taken before cancer was diagnosed.

          2. The people in the lowest tertile of IGF-1 levels in this study had low IGF-1 levels: less than 17.8 nmol/L. This is lower than the average levels observed in vegans in (Allen et al 2000).

          3. As I wrote before, according to the Allen et al 2000 study, the difference between IGF1 levels of vegan and meat eaters is small: (the average level is 18.5 in vegans vs. 20.1 in meat eaters).

          • JeffW

             Prospective case-control? That’s a new one on me. A prospective study by definition looks at a topic over a long period of time, while a case-control study is a snapshot in time. This was actually a case-control study, derived from data from a larger prospective study. At any rate, this is not the kind of study you want to try to make a case with; the statistical significance of the results is too small. In other words, although the study seemed to indicate no particular difference (for reasons as I explained above- a case-control is far from ideal for nutritional studies), the poor statistical power they got from this study indicates that the could very well have been by chance and if they repeat the study, they may well get the opposite results next time.
            By the way, DT, I feel as if every time someone wants to stand up and express themselves, you take a shot at them. Keep this up and no one will want to play with you anymore. I like to think of this as a forum where members support and encourage each other and whose comments show respect and encouragement. But I feel that you are violating these unspoken rules of courtesy and graciousness. I’d like to request that if you want to continue on this site that you try to be a bit more discrete in your comments.

          • fon

            first time here,and no opinion on this nutrition issue.but it seems to ,that ALL the hostility is and pot shots aare being directed AT DT,not from DT.and for what?for presenting the other side of the story? and doing it without a hint of hostility!! how dare he disagree with you all.

        • Guest

          Well this is the closest subject to my question, so here goes. I am 67 year old make and was diagnosed with prostate cancer (Gleason=8) four years ago and immediately switched to a strict vegan nutritional base. I’ve been an avid fan of Nutrition Facts (post them on my Pinterest site daily). For the first time I had my IGF-1 level checked (my doctor didn’t have a clue as to why) after reading/hearing about the beneficial impact of a low IGF-1. Mine is now 105 (very low?) and my testosterone is over 800; just as the doctor’s video mentioned! But is it low enough to combat my prostate cancer (recent PSA=7 up from 5.8 4 months ago)). Most of my blood work is terrific (HDL=71 LDL-74, Triglycerides=38).

          It is really hard to develop targets for some of these tests and I want to better understand how I should proceed. Current literature is all over the place and none/few address prostate cancer and nutrition.

          Tell Dr. Greger thanks for his guidance.

          Skip Stein

    • HemoDynamic, M.D.

      I love the graph with the baby with the baby chick in it’s mouth.  Gotta tell ya that I love your transitions in your presentation and your attention to detail within them.
      Just Fantastic Baby!!!

      Oh, great info as well (As always)

  • Veganrunner

    The studies continue to demonstrate that a plant based diet and exercise is a lifestyle we should all strive for!

    Eat your veggies and fruit and get moving. Pretty straight forward…….

  • I wonder if you could clarify something for me. I drink a lot of soya milk, I like it and have found I have been able to come off HRT since drinking it (I’m post menopausal). I watched a Dr John McDougall video on YouTube last night where he said that soya milk increased IGF-1 to even higher levels than milk from a cow. I’m sure I’ve seen a video of yours where you said that drinking soya milk was actually beneficial in terms of lower breast cancer rates. In your opinion, is soya milk safe for me to drink or not? I’m in the UK where the soya milk is certified GM free. 

    • Doug R

       Just to be on the safe side, Sue, maybe you should switch to rice, oat, hemp or almond milk. You probably won’t have to go back on HRT, now that you’re “over the hump.”

      • I wasn’t terribly impressed with rice milk when I tried it and although I like nut milks they are quite expensive to make. I might have a go at making some oat milk – I hadn’t thought of that. Soya milk is so much easier to drink because I can buy it in cartons from the supermarket fridge – I will cut down though (have been getting through up to 2 pints a day some days).

    • April Lillie

      Dr Mcdougall actually pinpointed isolated soy protein and not whole soy products such as soy milk. Many of his recipes use soy milk and tofu and he said it was safe. It’s the processed meat substitutes he cautioned against that were made with isolated soy protein such fake chicken . Note that does not include seitan which is made of wheat gluten flour.

      • When Dr McDougall mentioned soya milk I hadn’t realised you could get milk made isolated soy protein. The milk I buy is made from hulled soya beans, so thanks for that – makes me feel a bit better.

    • Toxins

      Dr. Greger covers how much soy is a safe amount in his future videos. As a sneak peak, the safe range is between 3-5 servings. More than that and you risk IGF-1 increases.

      • You can see into the future? Is that 3 – 5 servings per day, week or month? Also, how much is a serving?

        • Jo

          It’s on the current DVD, “Latest in Nutrition, Volume 10,” I often visit his site to see the subjects of videos to come. I purchased “Volume 1” … and hope to get the collection one day. But, until then, I check out his daily videos.

        • Toxins

           I have access to the future videos of this volume. 3-5 servings per day of soy, Typically, 1/2 cup of soybeans or tofu constitutes a serving and 1 cup of soy milk constitutes a serving.

  • Tara Martine

    Thank you for posting these great videos on IGF-1!  A question I have is do you know if there has been any research done on the effect of eating soy protein isolate on blood levels of IGF-1?   Would love to hear your thoughts on this topic.  :)

  • Artist117

    OK.  Now I am worried.  I am a 67 year old woman who was diagnosed with low IGF-1   2 1/12 years ago.  I was told I had the level of a 95 year old.  An expensive  product called Secretropin was prescribed – sprayed under the tongue.  No one has ever suggested that I be re-tested.  I am not a vegan.  My primary sympton was excersize intolerance and, although I don’t like being dependent on a med and have tried to do without it, I seem to do much better with it.  Cancer incidence in my family is very low but my mother had severe osteoporosis and other relatives had diabetes.  My father had Parkinsons.   Are any of these related to IGF-1?  What causes low IGF-1 and what should one do about it?  Other than increasing my animal intake, what could I do naturally? I have no known problems at present except the low IGF-1 and low thyroid for which I take Naturethroid. I know that you can’t diagnose me from this info but a general discourse on low IGF-1 would be very interesting.  Thank you.

  • AliceJ

    That’s all well and good.
    But here’s the bummer about going vegan whole-hog (pardon the expression):*  I’ve lost somewhere between 15-20 pounds, and people have started to notice.*  My
    knees have been kinder to me than they have been for some time.  As a
    result, I am starting again to run some with joy, swimming more laps
    with vigor and doing some yoga poses that have eluded me for a while
    (some I still can’t do).*  My hair is thicker (go figure).*  My skin is softer.*  The
    other day when I went to two grocery stores to take advantage of  the
    “Senior Discount,” the gatekeepers of the checkout lines didn’t believe
    that I was over 65.  I had to offer to show them my driver’s license. 
    In essence — I was carded.
    So what’s the problem?  I’m going to have to get a whole new wardrobe. 

    Thanks, Dr. Greger.

  • From Here To Whole

    Thank you for posting this fascinating series of videos regarding IGF-1 levels. I am a whole-foods, plant-based nutrition/health coach, and decided for the sake of experimentation to see what my levels are as someone following a vegan diet. The healthy range given was 65-250. My level was 175. That seemed rather high (perhaps?) for someone who consumes no meat or dairy. Is that indeed a high number, and if I’m otherwise very healthy, should it be cause for concern? Colon cancer runs in my family, so I’m interested in being proactive to decrease my risk. Again, thank you for this, and all of your videos, Dr. Greger.

  • Nicholas Christos

    The study that you cite from the British Journal of Cancer regarding testosterone is very flawed because the average age of the meat eating men in this study is 52 years old, while the vegan population of men (ONLY 260 MEN) is only 42 years old, and the testosterone levels in men decrease substantially every decade after 30, so I think to report this as fact is incorrect. The levels of the meat eating men is less because they are older and the vegan men levels is higher because they are younger.

    • Back-transformed means presented with 95% CI in parentheses. Values are adjusted for age (in categories of 20–29, 30–39, 40–49, 50–59, 60–69, 70+),smoking status (never, past, < 10 cigarettes/day, 10+ cigarettes/day), vigorous exercise (< 2, 2–4 5+ hours/week), time of day of venipuncture (< 10, 10–13.29,13.30+ hours), time since last meal at venipuncture (< 1.5, 1.5–3, 3+ hours) and time between blood draw and processing (1, 2, 3, 4+ days). aInsufficient serum
      led to IGF-I measurement being unavailable in 1 subject, SHBG in 9 subjects, T in 20 subjects, FT in 25 subjects, A-diol-g in 5 subjects, LH in 20 subjects and total cholesterol in 8 subjects. bP value is test of heterogeneity.

    • Also, vegans had higher testosterone levels than the vegetarians and they were similar ages. Other studies have shown similar results.

  • Nicholas Christos Here is the study, see for yourself.

  • GaryR

    Are there any figures for people who eat meat but do not consume any produce containing milk? My interpretation from the 3 sets of figures above is that meat makes very little difference in igf-1 but eliminating the other animal products provides the change. After reading that dwarfs with laron-syndrome have never had a single case of cancer, it’s clear that their unique igf-1 levels make the difference. If only we were foccused on igf-1 reducing methods rather than improving the current main stream cancer treatments (which aren’t working so well), maybe cancer could be prevented in the first place. With the amount of hormones found in milk products naturally destined for baby cows, it is quite astonishing that as a species we have (the majority anyway) accepted milk as being healthy to humans, simply because the people selling it to us told us so!

    Wake up to dairy. By waking up without it.

    • Ben Colin

      would be very interesting for me as (ex)paleo too. Concerning just this study, it seems that meat has no effect on IGF-1, but milk (and/or eggs) has.

  • Rebekah George

    I’d love to see your opinion/findings on isolated soy protein in foods. I saw a video somewhere a long time ago showing that soy protein isolate was 4x more potent than dairy at increasing IGF-1 levels. I’ve been avoiding foods that contain isolated protein (especially soy) ever since but haven’t been able to find the original video. (I think it may have been on the lecture series?)

    I try to eat primarily whole foods, and my diet is completely plant based. When opportunities come up, I try to share what I’ve learned about healthy eating with friends and acquaintances. I’ve had many people ask me about soy, and I tell them to avoid the isolated protein, but eating foods made with whole soy beans is fine. I’d love to be able to point them toward the evidence to back this. I find many articles/videos on your site about soy in general, but I haven’t been able to find one specifically addressing the isolated protein.

    Thanks for all you do!

    (I recently learned that Post Foods is jumping on the protein bandwagon and has added isolated soy protein to Grape-nuts (and possibly other cereals).)

  • jms

    Despite being vegan for 24 years, my IGF-1 level equals the carnivore level reported here. I eat fewer daily servings of soy than the safe level shown. What other factors might explain my high IGF-1 level?

  • What do you make of this study where vegans didn’t have raised T?

  • Psych Doc

    Here is an interesting link to studies in which they are injecting human placental extract to INCREASE IGF-1 as a means of slowing the aging process.

  • Find strict whole-food plant-based diet people and see the IGF-1 binding protein in them, similar to this study. I am one and do physical activity too. I gave this article to a chiropractor, who uses a wholistic process to help people, similar to the wholistic of T. Colin Campbell.

  • Arwen Carlin

    Dr. Greger, is it any meat that raises IGF-1 levels or just meat that’s been treated with growth hormones?

    • Thea

      Arwen: It is my understanding that the IGF-1 problem is in the animal protein itself, not the hormones. (Though the hormones can be an added problem.) Hence, any animal protein: flesh, dairy, and eggs is going to raise IGF-1 to cancer promoting levels. I’m not an expert, but that is how I understand the IFG-1 video series that you see on this site.

      Hope that helps.

      • Frasier Linde

        That is the conclusion drawn on this site, but I haven’t seen evidence to support it. Since vegetarians and meat-eaters had virtually the same IGF-1 levels in the example cited in this video, it appears that eggs and/or dairy (which commonly contains growth hormones) may be the culprit and not all animal protein.

        • Thea

          Frasier Linde: re: “it appears that eggs and/or dairy (which commonly contains growth hormones) may be the culprit and not all animal protein.” But eggs do not have added growth hormones. What eggs and diary have in common and what makes sense for the IGF-1 issue is the animal protein. I’m not saying that added hormones are not problem. I’m saying that problems with animal products go way beyond the issue of added hormones.

          I haven’t watched this series in a long time. But if memory serves, the video series does a good job of explaining why the problem is animal protein in general, and not a specific animal product or product(s). I understand you don’t find the evidence compelling. I do.

          re: “Since vegetarians and meat-eaters had virtually the same IGF-1 levels in the example cited in this video…”

          If I understand your text, you appear to be making an argument that is in favor of the generalization of animal protein = too much IGF-1 understanding. Both vegetarians and meat-eaters are eating animal protein. And they both have problems with IGF-1 levels. It’s only after eliminating all animal protein that a person gets their IGF-1 levels under control. Here is a quote from the video:

          “The aim of this study was to determine whether a plant-based diet is associated with a lower circulating level of IGF-1 compared with a meat-eating or lacto-ovo-vegetarian diet, and this is what they found. Only the vegans had significantly lower levels. And the same relationship found with IGF-binding capacity. Only the vegans were significantly able to bind up excess IGF-1 in their blood streams.”

          • Frasier Linde

            My parenthetical about growth hormones refers only to dairy. However, eggs and dairy are both much more commonly allergenic and pro-inflammatory than meat or fish. The fact that only the vegans in the study had significantly lower levels of IGF-1 could mean that eliminating all animal protein was necessary, or it could mean that eliminating eggs and/or dairy was necessary. Without a group eliminating eggs and dairy but not meat and fish, it is inappropriate to draw the conclusion that animal protein is universally problematic from this or similarly designed studies.

          • Thea

            Frasier: FYI: I understood what your parenthetical was referring to. That was my point.

            Is your argument that allergies and/or substances that cause inflammation affect IGF-1 production? I may simply not understand your point, but that doesn’t make any sense to me. I feel these videos do a good job of explaining exactly how animal protein affects IGF-1 levels. I have never heard of an alergic reaction triggering IGF-1 production in the body. It’s an interesting thought though. Are there studies that link allergies to IGF-1 production? Are you claiming that all those vegetarians and omnivores are having allergic reactions to dairy and eggs, but not (perhaps) meat?

          • Frasier Linde

            The allergenic and pro-inflammatory potentials are other things eggs and dairy have in common besides just animal protein—whether those properties affect IGF-1, I don’t know. A more striking commonality is that they are both naturally designed to feed growing animals, so it would make perfect sense for them to increase IGF-1 levels more than meat or fish. I’ll repeat the rest of my last reply, as you seem to have missed it as my main argument:

            “The fact that only the vegans in the study had significantly lower
            levels of IGF-1 could mean that eliminating all animal protein was
            necessary, or it could mean that eliminating eggs and/or dairy was
            necessary. Without a group eliminating eggs and dairy but not meat and
            fish (not to mention other uncontrolled factors such as what the animals
            are fed), it is inappropriate to draw the conclusion that animal
            protein is universally problematic from this or similarly designed

            P.S. The video explains why it *looks like* animal protein affects IGF-1 levels, but it doesn’t even attempt to address “how.”

  • blade78

    why does that “movie” spend so much time showing flying charts etc and so little time with the actual numbers on the chart so someone can read and see whats going on?

    • Thea

      blade78: These videos are meant to be summaries. For anyone who wants to get into the nitty-gritty, you can use a combination of the pause button for the video and/or go directly to the study source. Under every video is a section label titled, “Sources Cited”. You can expand that section and follow up with the original studies if you see a topic that particularly interests you.

      Personally, I found the numbers presented in this video (above the bar charts) to be sufficient for my needs, and that the flying charts where highly amusing and kept my attention. So, this video worked well for me.

      Good luck.

      • AliceJ

        Thanks, Thea. Your comments were helpful.

  • Tim

    Low amounts of IGF-1 can cause a lower quality of life and the appearance of being more aged *ie, skin more loose, less elasticity, smaller muscle, weaker bone, slower injury healing, etc”.
    IGF-1 is one of the major youth hormones in our bodies and many Hollywood celebrities and athletes supplement growth hormone (which is what IGF-1 is).

    Not everyone is at risk of developing IGF-1 cancer tumors. Let’s get that straight. This article doesn’t actually give you the percentage of people who are at risk of those types of cancer.

    Next, if you look at weight lifters who take strong dosages of growth hormone, you don’t see really any deaths or side effects. You see men living one hell of a high quality lifestyle. Are there risks with higher IGF-1? For A FEW unlucky people, yes, they would be at risk of cancer growth. For MOST people, this is not a risk and they can have high growth hormone levels well into their old ages and get lifestyle benefits from it. The biggest side effect would be an enlarged heart in a small number of people who are taking pro-body-builder levels of growth hormone.

    Don’t let articles like this mislead you are ‘scare’ you about growth hormone.

    • Toxins

      I don’t think anyone would agree that weight lifters are a model of health. These people supplement vast quantities of protein, the diet is not sustainable for a long healthy lifestyle. The IGF-1 issue is very real. It does not cause immediate death, it leads to chronic disease.

      “In this regard it is of special concern that male adolescents in the fitness and bodybuilding environment consume high amounts (60–80 g/d) of leucine-rich whey- or casein-based protein concentrates to gain muscle mass, a procedure which is often associated with the development of acne…it is frightening to realize that more than 85% of adolescents of Western countries exhibit acne, whereas individuals of non-Western populations like the Kitava are not affected by this disease and other mTORC1-driven diseases of civilization.3,149 This implies that the majority of our Western population is living with over-activated mTORC1 signaling, a major pathogenic factor, which probably may pave the way for the development of other serious diseases of civilization”

  • Oliver Pilon

    Im confused. Isnt IGF-1 the human growth hormone
    thats good to stay young etc? (im a man and my
    desire is to stay as young and virile a man i can
    be for as long as possible).

  • James Greathouse

    This medical doc, Sara Gottfried, MD, is down playing IGF-1, what’s Dr. Gregor’s take on this data?

    • Joseph Gonzales R.D.

      I don’t see any data? Looks like a neat site with well-written info, but no listed studies or links to research. That would be helpful to try to help answer your question. Thanks, James.

  • ldombovic

    I got a blood panel recently to prove to myself, and my family, that a whole plant food diet is health promoting in every way (5 months in). Part of my blood panel included my testosterone levels. My docs response was, “Your levels are a bit high, stop taking hormone supplements if you are.” I do not take hormone supplements. Just the whole plant foods…

    I read nutritionfacts’ material on the subject. The IGF1 info shed some light on why my levels are high. Below are my levels. Please let me know if this is consistent with that of a vegan’s testosterone levels ( I am 25). I worry about my prostate. Thank you!

    Average Range Mine
    Testosterone Total 250 – 1100 ng/dL 1403
    Testosterone Free 35.0 – 155.0 pg/mL 162.8

    I do take a 1mg finasteride supplement daily to keep hair on my head. I read that prostate supplements (higher dosages of finasteride) can cause an increase in testosterone.

    • Joseph Gonzales R.D.

      Hi Idombovic. Thanks for reposting your comment unfortunately I am not family with that medication. I suggest asking your doctor about it’s safety. I’ll double check with one of our volunteer doctor’s who help out here. Give them some time to respond. I have not heard of folks going on a plant-based diet having spikes in testosterone.

      • ldombovic

        Hello Joseph. This video on IGF1’s mentions that vegans have higher testosterone. I never had a blood panel before my change to a plant based diet, so i do not have a baseline for that. If you happen to know the average plant-based eater’s testosterone range, that would be great. I will be awaiting your response. Thank you.

        • Joseph Gonzales R.D.

          Wow thanks for clarifying it does say vegan men have been found to have higher testosterone levels, but the authors conclude “Vegans had higher testosterone levels than vegetarians and meat-eaters, but this was offset by higher sex hormone binding globulin, and
          there were no differences between diet groups in free testosterone, androstanediol glucuronide or luteinizing hormone” So that is reassuring.

        • Joseph Gonzales R.D.

          Testosterone ranges are not different. They are not based on diet. It also depends on age. Your doctor will be much better answering this question than me ;-) Ask her or him if this is right. Adults 20-39 years: 400-1080 ng/dL, 40-59 years: 350-890ng/dL. Lastly, I heard from one of our volunteer docs and they think the medication might be the issue. Again, I suggest discussing with your doctor. Thanks for all the comments and nice posts!

  • Johan Wallström

    Lol, those baby graphs! I was gonna link this video as a reference to a LC-group before I saw them, but they just don’t add to the argument =D Despite that, nice video tho!

  • Jordan

    What about this study

    ” There is good reason to suspect that low-fat vegan diets tend to down-regulate systemic IGF-I activity; this effect would be expected to increase stroke risk in vegans. Furthermore, epidemiology suggests that low serum cholesterol, and possibly also a low dietary intake of saturated fat–both characteristic of those adopting low-fat vegan diets–may also increase stroke risk. ”

    IGF-I activity may be a key determinant of stroke risk–a cautionary lesson for vegans.

  • Joe Nunes

    its essential to eat trigger foods that produce 1gf1 it burns stubborn fat/this is a witch hunt to promote big pharma…thats why people are so fat to begin with/insulin control is not the issue morons………………its promoting igf1 and at the right times/doctors doctors and big PHARMA……..want you sick and fat with carbs….because there are billions of dollars made every year keeping you loaded with addictive carbs and bullshit yo yo diets……………..industrial complex murdered JFK……and BIG PHARMA are slaughtering humans for the almighty dollar…..and the doctors kiss their asses as well.get smart america.metabolism burns fat………..not insulin restriction……………..MAT TISSUE NEEDS TO BE STIMULATED……….F ALL YOU CON ARTIST DOCTORS………………….

  • Joe Nunes


  • Just me

    I know that IGF-1 is needed for maintaining/building bone. Does anyone know what levels are needed for that and how this research fits with that need? What’s the sweet spot between not increasing cancer risk and not increasing bone loss risk?

  • Charma1ne

    Is the information in this article still current? I listened to a the recent fat loss conversations summit hosted by Dr. Jonny Bowden Phd (a lot of very well known physicians were featured). He claims that IGF-1 is the missing factor in obesity based on his own and the research and work of Dr. Raffelock who apparently analysed over 2,500 IGF-1 lab results in his long career. Nowhere is there a warning about cancer such as is found in this DVD. In fact a person is positively encouraged to raise IGF-1 levels to help change your matabolism to get lean and fit via the food you eat and strength training. What those foods are I don’t know without spending money to find out. I would really love an update based on this latest research by physicians such as Dr. Bowden et al.

  • Joyce Raftery

    I drink raw goat milk from a farm and also eat pasteurized goat yogurt and butter and goat kefir. Does raw goat milk have IGF-1? Do the other goat products have it? I know that goat milk has less saturated fat than cow milk. Is goat milk a healthy product for adults to consume? Thank you for sharing all your research with us!

    • Thea

      Joyce Raftery: After watching the NutritionFacts series on IGF-1, here’s what I understand: Animal protein causes our bodies to create more igf-1 than is needed or healthy and this leads to cancer growth. Hence, it’s not about how much igf-1 is in your goat milk. The problem is that your goat milk has animal protein in it. And then, as you mention, there is the problem with saturated fat, which even if less than cows milk, would be way more than healthy. And then there is the problem with hormones that come naturally in all breast milk. (Breast milk is designed to grow a baby into adulthood as fast as possible.) I can’t think of any reason to believe that goat milk, raw or otherwise, would be healthy for any human past weaning. For an overview of the science behind dairy (most of which would apply to goat milk as much as any other dairy), see: