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Too Much Soy May Neutralize Benefits

Vegans consuming 7-18 servings of soy foods a day may end up with circulating IGF-1 levels comparable to those who eat meat.

October 4, 2012 |
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Transcript

We know what happens when men with active prostate cancer start eating a vegan diet, the progression of their cancer appears to reverse, to get better—no drugs, no surgery, no radiation, just a vegan diet and other healthy lifestyle behaviors. Cancer markers in the control standard American diet group tend to get worse, and in the vegan diet group they tend to get better, the blood of those on a plant-based diet suppresses cancer growth about 8 times better. We're talkin' change on a genetic level diet and lifestyle changes switching on and off gene expression, delaying or avoiding the need for surgery and conventional chemo/radiation altogether.

I've already gone through that in videos past, but what if you did the same thing, men with prostate cancer, but this time—half in the control group and half in not just a vegan diet group, but in a heavily soy-based vegan diet group. How much soy are we talking about? 7-18 servings a day, for an entire year. That’s like entire blocks of tofu, or 7-18 glasses of soymilk—that’s like 4 quarts a day, all year round. What do you think happened to their IGF levels at the end?

The IGF-1 levels of the control group in the study didn’t drop at all, started high, stayed high. In a varied vegan diet—protein from multiple plant sources, all different kinds of benas, whole grains, etc—after years you can see IGF levels drop like this from baseline.

What happened to the drowning in soy vegan group. Did their levels drop too? With that much added soy, the vegans in the study got literally pounds of more protein in their diets than the meat-eating controls, but it was all added plant protein. Soy, however, one of those rare plants that mimics the protein profile of meat. So with that much more animal-type protein in their diet were they even worse?

Surprisingly, they ended up with values about same as the meateaters. But wait a second, in Asian countries, where they eat the most soy, they’ve traditionally just had a fraction of our breast and prostate cancer rates. Well the researchers found something interesting, the isoflavones, the phytoesterons in soy, may actually bump up production of IGF binding protein. So even though they had similar levels of IGF in their blood, in those eating vegan more of it may be bound up and unavailable to stimulate as much cancer growth.

Also, even in China and Japan, they don’t eat 7-18 servings of soy a day.

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

Doctor's Note

The allusion to stopping cancer progression through diet is a reference to Dr. Ornish's remarkable work featured in my video Cancer Reversal Through Diet. The eight-fold higher cancer cell growth suppression documented in those eating plant-based diets can be found in Developing an Ex Vivo Cancer Proliferation Bioassay. It's important to remember in this discussion that soy food consumption is associated with an array of health benefits. See, for example,Breast Cancer Survival and SoyThe Effect of Soy On Precocious Puberty, andSoy Foods & Menopause. The question really just comes down to the topic of tomorrow's video, How Much Soy Is Too Much?

For some context, please check out my associated blog posts: How Much Soy Is Too Much? and Foods That May Block Cancer Formation

In the meantime, if you haven't yet, you can subscribe to my videos for free by clicking here.

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

    The allusion to stopping cancer progression through diet is a reference Dr. Ornish’s remarkable work featured in my video Cancer Reversal Through Diet. The eight-fold higher cancer cell growth suppression documented in those eating plant-based diets can be found in Developing an Ex Vivo Cancer Proliferation Bioassay. It’s important to remember in this discussion that soy food consumption is associated with an array of health benefits. See, for example, Breast Cancer Survival and Soy, The Effect of Soy On Precocious Puberty, and Soy Foods & Menopause. The question really just comes down to the topic of tomorrow’s video, How Much Soy Is Too Much?

    In the meantime, if you haven’t yet, you can subscribe to my videos for free by clicking here.

    • Frank

      Quinoa is another complete protein like soy.  Have there been any studies showing whether quinoa consumed in large quantities may also have detrimental effects on IGF-1?

      • beccadoggie10

        Quinoa is a seed. It may be a complete protein, but is not estrogenic. Soy is a xenoestrogen.

    • DT

       In the series on IGF-1, Dr Greger claims the following:
      Animal protein -> higher IGF1 -> less cancer cell growth/more cancer cell apoptosis (in vitro) -> less cancer incidence.
      However, the Dewel et al paper which is mentioned in this video have some observational data which doesn’t support the above chain:

      1) There was no statistically significant association between animal protein consumption and IGF-1 levels.
      2) There was no statistically significant association between animal protein consumption and LNCaP growth or apoptosis. In fact, there was an “almost significant” positive association with LNCaP apoptosis.

      On the other hand, vegetable protein had a weak positive association with  LNCaP cell growth (which is bad thing).

      • Guest

         The difference between the IGFBP-1 in the experimental vs. the control group at the end of the experiment had a group p-value of 0.02 which shows a strong statistically significant difference. However, although there was a trending toward higher IGFBP-2 and IGFBP-3, the experiment lacked power to claim significance. Apparently, and increase in soy isoflavones in the diet was not adequate to compensate for the 30% increase in protein intake among these omnivores. We should keep in mind that this was not an experiment with a low protein vegan diet, but a high protein mixed animal and vegetable protein diet and it would not be advisable to apply the results of this study to people who are on a vegan diet. Even so, it showed some benefit of soy isoflavones, although the authors’ advice not to exceed protein requirements should be heeded by all. In the light of other studies which Dr. Greger has presented and additional studies available, we have good reason to believe that a moderately low protein vegan diet will indeed result in less cancer initiation and promotion and greater cancer cell apoptosis.

        • HemoDynamic, M.D.

          Excellent!

        • DT

          1. When you consider a theory, you shouldn’t just look at evidence that support it, but also at evidence that refutes it.

          2. The Dewel et al study was multiple factor intervention (including exercise and stress management), so it is impossible to tell if the effect was due to the soy isoflavones.

          3. Which studies did Dr. Greger present about low protein vegan diet? The Barnard papers? These people on these studies were on the Pritikin diet which is not vegan.

  • http://www.facebook.com/profile.php?id=640861216 Gary Yuen

    Interesting. I only take soy sometimes and only fermented (as miso or natto). Think that’s a bad idea?

    • nicole

      No, fermented soy is some of the healthiest things a person can eat. Good for being able to eat natto, I love the stuff too. The stuff you should avoid is the really concentrated things like soy milk and copious amounts of tofu. If you eat around the same amounts as the typical asian (which while plentiful, isn’t completely overboard) you’re probably good. 

    • beccadoggie10

      How do you prepare miso. Do you mix it as a sauce to pour over veggies or rice rather than cook with it?

  • gary yrag

    If we eat the whole soy bean (edamame), as opposed to tofu or soy milk, we will probably get more phytonutrients and fiber, and we’ll also be less likely to eat too much soy. The soy bean can be purchased in many health food stores in dried bean form, similar to other dried beans; it’s soaked overnight and then steamed. A little crunchier than other beans, so goes well with oatmeal or barley. Has a mild, nutty flavor.
    The exception is miso, which i’ve heard from Dr Greger in other videos confers some special benefits, as a result of the fermentation process (sodium content aside).

    • http://www.facebook.com/profile.php?id=640861216 Gary Yuen

      It’s also worth checking out who has used soy the most, chinese medicine. They classify black and yellow as different (and not sure of mention of other colors).

      Some sample link here:
      http://leungschineseherbnews.blogspot.com/2007/07/part-2-of-2-soybean.html

      One other book has a long list of properties but also contraindications:

      black: Excess weakens spleen and can cause phlegm disorders.
      yellow: Excessive consumption leads to: Qi stagnation in abdomen, abdominal distension and possibly formation of dampness and phlegm.

      Interesting one term of cancer for chinese medicine is phelgm ball.

  • Fnugg

    Hi,

    There is a Norwegian study that says soy treated at a very high temperature results in a soy product that is not so beneficial.

    Study: 

    Lars Henrik Høie, M.D.: Cholesterol lowering effects of soy protein, and how denatured protein may increase the risk for cardiovascular disease, Institutt for helse og samfunn, Universitetet i Oslo, januar 2011.

    article excerpt:

    Harmful soymilk Soy and dairy products with long shelf life are heat treated. They may increase the risk factors for cardiovascular disease by nearly 20 percent, according to a Norwegian doctorate.

    http://www.forskning.no/artikler/2011/januar/275961

    Could the soy used in the study in the video be of the type that is treated at a very high temp? Would home made tofu, soy milk etc perhaps show a different result?

    Thanks

  • Fnugg

    Hi,

    Have a question, which is probably pretty silly but every time you have mentioned about vegan blood and its effect on cancer cells, I wonder. My question is  does the benefical side of vegan blood also carry over if given in a blood transfusion? Could it have a beneficial effect if given to a cancer patient? Silly question, but …

    Thanks.

    • Nepst

      Hi Fnugg: I got the same question! Thanks.

    • Logan

      Not silly at all, I have been thinking the same thing since I first heard him mention this…

  • Mfravaga

    Ok Now we know that eating kilo´s of tofu per day isn´t healthy. It would have been more interesting to compare Vegans consuming 7-18 servings of soy foods, to meateaters consuming 7-18 servings of meat per day, and eating the same amount of proteins per day.

    (How much is that by the way, 7 to 18 servings? 1 to 2,5 kilo per day?
    Try think of a day with 18 servings of meat! or more than 12 servings a whole year long!)

    ….Or does this findings actually prove that an unheathy vegan diet (with loads to much proteins)  is as healthy as usual “healthy” meateating (with the correct amount proteins) diet??

    Martin

  • Vegicatster

    How much is a serving – 1/2 cup, one cup.  I would think it depends upon what you are eating – tofu, soymilk etc.   I mean – 12 – 18 servings sounds like a lot. 

  • Matthew Ciuccio

    I like soy, but I am glad I don’t like it soy much to need 7-18 servings a day. Phew.

    • Thea

       Matthew:  I don’t know if it was a typo or deliberate, but I thought that this was funny:  “… I don’t like it soy much…”

      :-)

  • Maria

    This study focuses on an exaggerated amount of soy per day…. what are the effects based on a average number of servings of soy per day?  Does any research exists that shows that?

  • Merle

    I noticed that you were “advertising” for “Silk” soy milk.  You should know that “Silk” has contributed to the ”Monsanto” side of the GM Labeling proposition on the ballot in California.  They did not give funds to the “Organic” Labeling Promoters but gave hundreds of thousands of dollars to campaign against labeling Genetically Modified Foods so we as consumers can make a choice.

    “Silk” is not alone and a lot of “industrial organic” companies have contributed to the “Monsanto” side of the proposition.  I just think your followers should be aware that not all so called “organic” health food is what it appears.  I find it appalling that companies like the producers of “Silk” play off the market to “health finders” but do not share an ounce of the philosphy and the goals of those trying to eat a healthy diet.   

    • Veganrunner

      thanks for pointing that out. 

    • http://www.facebook.com/profile.php?id=687926548 Mike Speer

      Interesting.  The main reason I buy Silk brink is because it is fortified with B12.  I wish more brands would do the same, but most contain no B12.

      • http://www.facebook.com/robinLA Robin Petersson

        Same here. It’s the only brand that has high fat and fortified soy that is palatable and also readily available. I fed my twins cow milk formula for the first year and after that switched to soy milk and found this brand was the best. I wish it was organic, but, doesn’t seem like you can get all the good stuff in one box.

    • http://healthygirlskitchen.blogspot.com/ Wendy@healthygirlskitchen

      The worst is Earth Balance!!!!

      • WholeFoodChomper

        What do you use instead of Earth Balance, then?

        • beccadoggie10

          I don’t personally use Earth Balance. Instead, I eat an ounce of seeds or nuts for my fat in-take. My husband, a non-vegan, does both. He eats nuts and Organic Earth Balance, as he loves nuts but cannot break the habit of spreading something on his English Muffins.

          In Italy, people spread a good quality olive oil on their bread and everything else for that matter.

        • irish vegan girl

          Earth Balance is also horrendous environmentally because of its use of palm oil. This is true for all margarines/shortenings etc unfortunately. And “sustainable palm” is a load of greenwashing….the RSPO is self policing and has members like Nestle and some of the other worst offenders. Best to avoid palm altogether. this recipe is great. it looks complicated but try it once and you will see its actually simple, tastes great too, and palm oil free :) http://www.veganbaking.net/other-vegan-treats/735-vegan-butter.html#.UTllCBxQFZ8

          • http://jolkapolkaskitchen.blogspot.com/ WholeFoodChomper

            Thanks for sharing! I may just try this. ;-)

    • beccadoggie10

      I suggest that perhaps Dr. Greger simply used the brand Silk as an example because many people have heard or are aware that Silk is a soy milk, and that he was not promoting the use of Silk or any other brand name. He does not like to give our brand names.

      From what I understand (and I don’t drink soy milk) one should not drink a glass of Silk to get the correct amount of protein needed. For example, McDougall “recommends that one use traditional soy foods, like soy milk and tofu, only as a SMALL part of your diet, at most 5% of your daily calories.”

      McDougall says “an example of sensible uses of soy might be:
      Soy milk to ‘moisten’ cereal, ‘not glassfuls’ as a beverage.

      “Synthetic soy foods,” like meats, cheeses, and soy bars, should rarely, if ever, be consumed. http://tinyurl.com/2679bj

  • Bgrune

    I generally find the information on this site to be interesting and informative but this entry seems to just be sowing confusion and soy bashing. I eat a large amount of soy in the form of sprouted organic tofu and organic miso on a daily basis but I come nowhere near the amount being discussed. I cannot imagine where they found people who eat this much soy. From reading the comments of other viewers I think many people took away the conclusion that soy is dangerous. I don’t think this video was very helpful.

    • Thea

       Bgrune:  I understand your opinion, because people do have the reaction you mention. 

      However, I completely disagree that it is a problem with the video.  I would offer this: This video is part of a series.  There is more coming where Dr. Greger talks about safe amounts of soy.  It is not fair to judge the video outside of the context of the series. 

      It should also be noted that both in this video and others Dr. Greger clearly discusses the benefits of soy.  Someone who comes away from this video thinking that reasonable amounts of soy is bad for people was not paying attention.  So, really this video is pointing out that there are amounts of soy which can be too much.  That’s not a big surprise or any kind of knock on soy.  You can have too much protein, too much water, too much just about anything.  That doesn’t mean the food is bad for you.  People need to learn this.

      I personally find it extremely helpful to know what the good range for various foods are.  How much protein is good for us?  How much soy?  How much water?  etc. 

      While it may seem ridiculous to you *and me* that people would actually eat 7, let alone 18, servings of soy a day, Dr. Greger has posted at least one video of a case study where a man did just that – and did experience health problems.  Similarly, I was at a lecture on soy a couple weeks ago and there were three case studies of people who, completely on their own, massively overdosed on soy, with negative effects.  My point is, letting people know what the upper safe amounts of various food are is a public service.

      More than that, though: What this type of study does is add one more bit of data to help us understand the big picture concerning the relationship of soy consumption to IGF-1 production.  By doing this study (and Dr. Greger sharing it with us), we learn that soy, which has a closer profile to animal protiens than many other plants, actually can have an effect on the body that is similar to animal proteins.  This is super fascinating because it lends support to the earlier videos’ conclusions about how the closer a protein is to the composition of the human body, the more it is likely to ultimately have a bad effect (by increasing the IGF-1 production past levels good for us).   In order to make a claim like that, we need lots of studies hitting the question from various angles.  This is just one more study doing just that, and I’m grateful to be told about it.

      This reply got way longer than I intended.  My apologies. And you are certainly entitled to your opinion.  I just wanted to give you and anyone else reading your comment a different perspective.

      • henry2403

        Great response Thea,

        I found this very helpful.

    • Thea

       Oh shoot.  I meant to add:  good for you on eating all that sprouted organic tofu!  That’s great.  You are a good role model for the rest of us. 

    • mike at the river

      I eat 1 container (6 oz)  of organic “Whole Soy & Co” soy yoghurt daily for lunch (6 g protein). Besides being delicious, esp w/their added fruit, the label says non-gmo. Hard to believe this much of this product is unhealthy.  Especially as co-workers wolf down hamburgers, dairy yoghurt, pizza, and frozen chicken TV dinners…Mike

      • beccadoggie10

        Meat has a high IGF-1 factor because I suspect, the persistent organic pollutant chemicals that are fat soluble and concentrate into the fat of livestock and the people or other animals that eat the meat. But, studies have found that high levels of soy also have an IGF-1 factor. So, it’s better to have low amounts of soy, even if it’s organic, than high levels.

        I did not know how high, high was so I googled one of the studies and found myself at Dr. McDougall’s web site for his newsletter. He or his staff assembled examples of common processed foods with significant levels of Soy Protein Isolates that one does not want to eat. Being new at the plant based diet, I tend to err on the side of precaution and avoid processed foods. Which, it turns out, is a good idea whether or not it’s organic.

        See: http://tinyurl.com/2679bj

  • Annapolis

    Thank you for this addressing this issue. I don’t eat nearly 7 to 18 servings of soy a day but my IGF – 1 is 198!  I have been vegan for decades.

    I am trying now to find a doctor who will order up the binding factory test. My regular doctor thinks it is an unnecessary test and had his staff person tell me to go to a specialist.

    He is the guy who didn’t even know what IGF-1 was!

    Ann
    Annapolis

  • Veganrunner

    Could it be that in the research they are using the same servings of animal protein as soy protein. People easily eat 7 or more serving of animal protein in a day. Breakfast- eggs and bacon, lunch- ham sandwich, dinner- 24 oz t-bone. 

    So what happens with IGF-1 levels if equivalent servings of soy protein is eaten as with the SAD which includes large servings of animal protein.

  • Nursejvw

    Are soy based products harmful if eaten 2-3 times per week? How many grams of soy per day are beneficial? How much soy is detrimental?

  • R Ian Flett

    The soy debate is a classic example of what’s wrong with so-called ‘nutritional science’. It’s clearly more complicated than the polarized protagonists think it is and it’s heavily contaminated by vested interests from the soy v dairy lobbies.
    As DT pointed out we need replication and refutation studies, not publication bias and zealous confirmation.

    Dr Greger’s contribution is a worthwhile hypothesis and deserves more than ‘Hallelujah’ dynamics. Attempts to refute the hypothesis are not oppositional, but a necessary hypothesis testing against all published evidence.

    Frequently in science when things get very polarised it’s because of hidden variables that neither side has considered. In this case we perhaps need to look more closely at the form in which soy is consumed. Natto, for example, seems to depend for its health benefits on the specific strain of bacteria used in fermentation (same as Jarlsberg cheese) that produce menaquinones (MKs). Also, the issue of sprouting is very interesting in that it produces new compounds and reduces others such as phytates. Fortunately, the MKs have a long half life so I don’t have to eat my natto daily. I would like to kow much more about the benefits of the fermentation of grains and legumes.

    • farseas

      Can you please be more specific on the mk-7 issue and the right type of bacteria that should be used to create natto that is mk-7 rich?

  • BPCveg

    R Ian Flett: I think that this is a useful comment and I am inspired to share my perspective on this topic.

    I think that people like you and the person by the alias ‘DT’ are contributing more value to this website than those who simply beat the drums behind Dr. Greger as if he is some kind of vegan rock star. Even though I think that Dr. Greger is doing a good job making relevant articles available and providing entertaining (and often informative) videos, we must remind him from time to time to analyze the facts dispassionately and provide fair evaluation of limitations that are inherent in studies. He should provide the same level of critique to studies that support veganism as to those that oppose veganism.

    Presumably, many of us are not just tuning into this website to get our morning dose of vegan validation. Hopefully some of us are trying to better understand the science of plant based diets. We musn’t forget that, to be understood, science must be always be challenged.

    Viewing your critique of scientific studies in the abstract, I think that studies are always going to have limitations – they just can never control all variables. As you point out there is always the possibility of a hidden variable, which explains any correlation. Another limitation is that studies typically only compare one dietary intervention (e.g. vegan diet) against the standard of what the general population eats. Differences seen obviously say little about what is optimal, since the control group (e.g. SAD diet) is so backward that virtually any reasonable intervention would show some improvement. For example, if a comparison is made between the health status of people who ate hot dogs without the bun to those that ate hot dogs with the bun, an improvement may be found by dropping the bun. But, it would be ridiculous to conclude from a study like this that eating hot dogs without a bun is somehow optimal.

    Therefore, I think the best studies can do is provide clues, which need to be explored by physiological research.

    Instead of simply focusing on inconclusive studies, I would like to see this website develop and critically evaluate the key mechanistic threads of reasoning in favour of plant-based diets, for example:

    1- We have seen that plant-based food are packed with more antioxidants than animal-based foods:
    http://nutritionfacts.org/video/antioxidant-power-of-plant-foods-versus-animal-foods/

    It would be useful to learn more about what physiological conditions affect whether the antioxidants reach the cells of our body. We should try to better understand what limits absorption and whether the antioxidants are actually active within cells. What diseases do antioxidants impact and what conditions affect this?

    2 – We have also learned that plant-based diets have far lower levels of chemical pollutants:

    http://nutritionfacts.org/topics/persistent-organic-pollutants/

    Since we are all living in a chemical soup, clearly our bodies are somewhat resilient to pollutants. I have always wondered what concentration of pollutants actually make a difference. So I think we need data to better appreciate what concentration of pollutant get absorbed by our bodies and the specific role played by these pollutants in shifting the balance from health to disease. I think this question is also important in connection with organic versus conventional farmed foods.

    3- Another complex topic is nutrient synergies. One of the themes of this website has been that eating produce is better than taking the equivalent nutrition in the form of pills. I think more research is needed to understand why this happens. For the same reason that vitamin C in fruits may be more effective than eating vitamin C pills, some foods like fish may seem to provide health benefits in certain studies, because the whole is greater than the sum of its parts. So simply dismissing fish on the basis that it has high concentrations of pollutants may be incorrect from a physiological perspective.  I don’t eat fish, but I still want to know why some studies suggest health benefits. Is it possible that this is because of synergistic effects? Or is is simply do to anti-inflammatory effects relative to SAD, as usually suggested.

    Anyway, I hope that Dr. Greger reads our questions and considers them when formulating new videos.  I would be highly interested in further comments on any of these topic areas.

  • BPCveg

    comment deleted.

  • R Ian Flett

    Here’s another variable that I had previously missed that might make even more sense out of the IGF-1 issue relating to a plant based diet. 
    It seems that low dietary methionine reduces IGF-1 signalling and so, in turn, methionine-reduction’s effects are correlated with calorie-restriction’s effects.http://www.oasisofhope.com/media/pdf/met_vegan.pdfOnce you consider that calorie restriction’s role in longevity may be dependent, not really on total calories, but rather on the total intake of methionine (less is better), then a new perspective emerges. Quoting http://www.nutritionj.com/content/10/1/107In summary, neither carbohydrate restriction nor lipid restriction appear to be responsible for the life extension caused by CR, while approximately half of the life extension effect of CR seems to be ascribable to protein restriction. A wealth of evidence indicates that methionine restriction might account for most or all of the life-extending benefits of protein restriction. Fortunately, a methionine-restricted diet is both feasible and tolerable, suggesting that it might be an attractive alternative to CR for those seeking the health-enhancing properties of such a plan. However, because the evidence provided above has been generated using animal models, further work involving human test subjects is necessary before firm conclusions can be made.Vegans have the lowest dietary-style intake of methionine because meat, fowl, fish, dairy and egg proteins are relatively high, while plants are low. There is a surprisingly high amount of statistical evidence to support the negative role of methionine in longevity, despite it being an essential amino acid. Plant proteins are generally much lower in methionine than animal proteins. This could also explain why fish never seems to benefit more than thrice a week as the assumed omega 3 benefits may offset by increased methionine. Recent Swedish studies indicateded that daily fish consumption increased ischemic strokes in women.Possibly better would be the fish oil capsules, although evidence varies widely. High omega 3 veggies, such as flax, may be even better still. Fish products now have the increasing problem of contaminants, the latest of which is plastics getting into their food chain even down to the plankton level.

  • R Ian Flett

    Sorry, but all my formatting disappeared on submission and it all crammed up.
    The last quote stops at “before firm conclusions can be made”, and the rest is my own, starting at “Vegans have..”

  • Ed1618

    Just a note. Perhaps lowering IGF1 levels might not seem the only way that soy protein might decrease cancer growth. In the China Study, p60, T. Colin Campbell reported on the effect of different kinds of high protein diets on foci response in rats. He saw a huge foci response with 20% casein, butt virtually no response with gluten protein – but also soy protein.  In this case soy protein, even if very high amounts, did not promote cancer growth any more than wheat protein did, while milk protein acted as a supercharged fertilizer increasing cancer growth many fold. In these experiments plant protein – including soy protein – at least in rats -, did not promote cancer growth even at high levels of intake.

  • Hathor42

    I don’t see how folks could get so many servings of soy without using isolated soy protein, which is a different beastie when it comes to IGF-1.  http://www.drmcdougall.com/misc/2005nl/april/050400pusoy.htm
    A whole food plant diet wouldn’t contain highly manufactured soy protein products, would it?

    • beccadoggie10

      If you eat a simple diet of whole foods and no processed foods, I don’t think you would need to worry about getting into the range of the IGF-1 factor with soy. With processed foods, it is definitely easy to get there. Serving/proportion size be it animal protein (when I ate animals) or soy is critical.

      Neither my non-vegan husband, nor I had ever eaten 7 servings of animal protein a day. Perhaps, that’s the reason we have not yet had cancer. And, I do not eat anywhere near 7 servings of soy protein per day. It’s more like a 1/2 cup or possibly the equivalent of one and a half cups — a half cup tofu and the rest in a black cuban bean soup which may contain black (soy) turtle beans and brown rice. The rest of my protein comes from a variety of vegetables.

  • http://www.facebook.com/IggyEvans Tracy Evans

    Dr. Greger – do you think that consuming a diet heavy in foods that contain soy protein isolate(as opposed to whole soy foods) would have this same effect on IGF levels?

    • Dr. Connie Sanchez, N.D.

      Soy protein isolate (SPI) is more concentrated in protein than are whole food soy products such as soy beans (edamame), tempeh or soy milk. In a study of 71 women randomly assigned either 40 grams of soy protein isolate or 40 grams of milk-based protein it was shown that both protein supplements increased serum IGF-1. It is also interesting to note that the soy protein isolate increased IGF-1 almost twice as much as did the milk-based protein (1). Isolated soy protein is a powerful growth promoter and has been associated with the development of breast, prostate, lung and colon cancer.

      1. Arjmandi BH, et al. Soy protein has a greater effect on bone in postmenopausal women not on hormone replacement therapy, as evidenced by reducing bone resorption and urinary calcium excretion. J Clin Endocrinol Metab, 2003. Mar:88(3):1048-54.

  • irishvegangirl

    Hi Dr. Greger…can you comment on the info floating around about soy not being acceptable for men/boys? I thought that info had been debunked but just ran into it again the other night when i was babysitting for an infant (boy) with very bad colic…I suggested dairy could be the problem but apparently her doctor told her not to try changing the milk, she did anyway but to another dairy formula; she was strongly advised by the baby’s craniosacral therapist as well as by a healer NOT to give soymilk to boys that its only ok for girls…can you comment or direct me to relevant information? All of that aside, you cant even GET non-dairy based formula in the UK or ireland as far as i know, which is very strange as there is no option for babies who have problems with dairy…seems very strange. (of course breastfeeding would avoid these problems, but the reality is that not everyone breastfeeds.) thanks

    • Thea

      irishvegangirl: It is really hard to find videos on this site, but Dr. Greger DOES have at least one video, if not more, which address the issue you are talking about. I tried doing a quick search for you and could not find the videos I was looking for.

      If you have more patience than me, I do recommend doing a search and watching several videos. One of them specifically talks about a man who started growing breasts – but that was only after consuming ***obscene*** amounts of soy every day. If memory serves, other videos which talk about soy will mention men/boys and soy, but may not be the sole topic of the video. Bottom line was that soy is just as good for males as it is for females as long as (like for any food) we are talking about reasonable amounts.

      One thought you might share to help educate someone: Dairy has estrogen/hormones in it, and diary affects boys (and girls) accordingly. Soy, on the other hand, has only plant stuff in it – and the plant / phytoestrogens that you hear about in the media have been shown to have positive effects on people’s health.

      Good luck.

    • Toxins

      Dairy milk raises estrogen and lowers testosterone in men, not soymilk. this is a common myth. This video describes the effects of both soy and dairy. http://nutritionfacts.org/video/dairy-sexual-precocity/

  • kyouran

    Some studies have found beneficial effects to IGF-1. Low IGF-1 is associated with shorter telomere length and heart failure, and it also appears to protect from atherosclerosis. So, clearly it can’t be all that bad?

    Cancer is uncontrolled growth and should be avoided, but the way I understand it is that insufficient IGF-1 inhibits the rebuilding of some of the aging structures in the body, so there must be some “minimum” IGF-1 level that is required to ensure that repairs can be made, which of course depends on stature.

    I’m not so sure whether stopping overall growth is the correct course of action to prevent cancer, although I do agree that it can be an effective treatment if cancer has been found.

    To use a metaphore: Should we fire the construction worker because his materials are defect? Wouldn’t it be better to just pause construction when that happens, fix the defects and continue the repairs? I’d like to hear your opinion on this.

    • Thea

      kyouran: I don’t believe anyone is saying that all IGF-1 is bad or “stopping overall growth”. Eating a plant-based diet does not stop overall growth. (If it did, vegan kids wouldn’t be so very healthy like they are.) A whole plant-based does not stop your body from creating the *right amounts* of IGF-1. What a plant-based diet *does* is stop your body from spiking IGF-1 (since the animal products are not eaten) in amounts that are so high, it feeds the cancer.

      To use your analogy, a plant-based diet makes sure the construction worker gets all the right materials, defect-free. That’s how I understand it anyway.

      • kyouran

        Well, this is my opinion on the matter:

        While getting the right nutrients is important, the problem with aging hasn’t really been in defects of the materials, but the blueprints used (the DNA deteriorates due to mutations).

        Also, IGF-1 levels are generally higher in children regardless of diet, but a vegan lifestyle does make them shorter; that’s why shorter animals tend to live longer as well, because their smaller body requires a lower total IGF-1 level for maintenance in later life.

        The real problem is at old age: the IGF-1 levels of older people are already quite low, and further lowering of IGF-1 may impair their maintenance causing muscles like the heart to start getting weaker faster. Cardiac hypotrophy is associated with low IGF-1 levels in older people.

        While low IGF-1 levels in children doesn’t impair their regenerative ability, it does impair their growth. In older people, IGF-1 levels may in fact be too low to ensure even an adequate regenerative ability.

        As an additional fact, it has been shown that lower IGF-1 levels are correlated with shortened telomeres, which is an effect you definitely don’t want in the long run.

        Because of the current controversy on IGF-1, I don’t think it’s best to “lower IGF-1 at all costs”, or at least not in the later stages of life. You can minimize IGF-1 in early stages of life because your body is essentially producing way too much anyway at that stage, but at really old age impairing a necessary regenerative ability too much may not be the thing you want.

        My opinion is that the key to living long is reducing IGF-1 in the earlier stages of life (let’s say up to 70-80 years) as it does accelerate the aging process, but after that it just becomes dangerous to do so.

        To fight cancer at older age, adequate screening can help detection of cancer, and only then should you temporary reduce IGF-1 to fight it, but continue as normal once it’s cured. IGF-1 has just too many benefits at old age.

  • Denis Spasyuk

    nice video