How Much Soy Is Too Much?

How Much Soy Is Too Much?
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To maintain the low IGF-1 levels associated with a plant-based diet, one should probably eat no more than 3-5 servings of soy foods a day.


So, we know 7 to 18 servings of soy a day may neutralize some of the beneficial effects of avoiding animal protein. At the same time, studies have repeatedly found that women who eat lots of soy appear to have a lower risk of getting breast cancer, and a better risk of surviving breast cancer than those who don’t eat soy. So is there some magic number of soy food servings we should shoot for?

So far we know that somewhere between 7 and 18 may not be so good, so more than 18 definitely gets the axe. This two year study found no effect on IGF levels of adding two servings of soy foods daily, whether they were tofu, soy milk, soy nuts, or the concentrated soy isolate found in plant-based meats, protein bars, or protein powder; still fine.

Still got a big range here. This study suggested 5 to 10 servings a day was bad— increased IGF—so we’re kind of slowly but surely narrowing down the safety window. Same year in Japan; three servings a day cleared the IGF radar. And then, that’s it. That’s all the science we have so far.

The bottom line is that legumes should be a part of everyone’s daily diet, which means lentils, peas, and/or beans, ideally with each of our meals—of which soy is an excellent choice. But, I recommend that we should probably stick to no more than 3 to 5 servings 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.

Please consider volunteering to help out on the site.

Images thanks to viviandnguyen via Flickr.

So, we know 7 to 18 servings of soy a day may neutralize some of the beneficial effects of avoiding animal protein. At the same time, studies have repeatedly found that women who eat lots of soy appear to have a lower risk of getting breast cancer, and a better risk of surviving breast cancer than those who don’t eat soy. So is there some magic number of soy food servings we should shoot for?

So far we know that somewhere between 7 and 18 may not be so good, so more than 18 definitely gets the axe. This two year study found no effect on IGF levels of adding two servings of soy foods daily, whether they were tofu, soy milk, soy nuts, or the concentrated soy isolate found in plant-based meats, protein bars, or protein powder; still fine.

Still got a big range here. This study suggested 5 to 10 servings a day was bad— increased IGF—so we’re kind of slowly but surely narrowing down the safety window. Same year in Japan; three servings a day cleared the IGF radar. And then, that’s it. That’s all the science we have so far.

The bottom line is that legumes should be a part of everyone’s daily diet, which means lentils, peas, and/or beans, ideally with each of our meals—of which soy is an excellent choice. But, I recommend that we should probably stick to no more than 3 to 5 servings 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.

Please consider volunteering to help out on the site.

Images thanks to viviandnguyen via Flickr.

Doctor's Note

This is the fourth in a string of videos on the role plant and animal proteins play in determining levels of the cancer-promoting growth hormone IGF-1. Also see IGF-1 as One-Stop Cancer ShopProtein Intake and IGF-1 ProductionHigher Quality May Mean Higher RiskAnimalistic Plant Proteins; and Too Much Soy May Neutralize Benefits. For the role soy plays in extending breast cancer survival, see Breast Cancer Survival and Soy. And, I’ve got dozens of other videos on soy.

For further context, be sure to check out my associated blog posts: How Much Soy Is Too Much? and Why Less Breast Cancer in Asia?

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

161 responses to “How Much Soy Is Too Much?

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  1. This is the fourth in a string of videos on the role plant and animal proteins play in determining levels of the cancer-promoting growth hormone IGF-1. See Protein Intake and IGF-1 Production, Higher Quality May Mean Higher Risk, Animalistic Plant Proteins, and Too Much Soy May Neutralize Plant-Based Benefits. For the role soy plays in extending breast cancer survival, see my latest video on the subject Breast Cancer Survival and Soy. I’ve got two dozen other videos on soy (and hundreds of others on more than a thousand topics).

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

    1. I’m having a hell of a time working out how much soya milk, tofu, tempeh, or soya isolate (ie. TVP) is in “a serving” – each site I’ve found on serving sizes has widely varying amounts listed. It’d be really helpful to have pointers to good, solid resources on serving sizes for soya products (in general, I mean; not for each specific product).

      1. The serving size cited in one of the above studies “Maskarinec” used the Chinese Food Composition Table which counted one serving size as 100 grams.  this is equal to about 3.5 ounces–about the size of a deck of cards.
        Here is a link to the International Food table:, nuts, and seeds.
        If that link doesn’t work then click this one: Go down to Table 1 and click on Pulses, Nuts and Seeds.

        I hope this helps.

        1. I appreciate the link to the table. With respect, I don’t actually think that table answers the question. 100 grams of what? The protein (and calories) in 100 grams of tofu is substantially different from the protein in, for example, soy flour. 

          I think the answer everyone is looking for is how many grams of soy protein per day is safe?
          In theory, for a male of my size, I need 60 grams of protein per day. Is it okay if 20 grams per day are soy? How about all 60? Could this be losing the forest for the trees?  Perhaps, but this is a science driven site and solid numbers are part of the science. “Servings” is not a number. Look at junk food servings. They’re all over the place. Thanks again.

          1. A cup of soybeans and soy milk = 1 serving
            A half cup of tofu= 1 serving.

            there is no dietary need to supplement protein as all whole plant foods contain complete proteins and caloric intake and expenditure is equivalent to protein needs.

            Soy protein powders are different from soy beans, as this is soy protein isolate lacking all original nutrients found in the bean. Soy protein isolate raises IGF-1 levels in humans twice as much as dairy does in 40 protein gram equivalents.

            1. Soy Protein Isolate (powdered soy) is generally recombinant DNA which as a whole bean has received vast amounts of Glyphosate (Roundup), Dicamba, or possible 2,4-D, an herbicide contaminated with 2,3,7,8-TCDDioxins.
              Could that have anything to do with the increased risk of cancer from this form of soya, in addition to it being more concentrated?
              I only use Miso and tofu from certified organic soybeans. Eden Organic miso and MoriNu certified organic soy.

                1. It’s in a huge range of vegan products, and you have to look at the ingredients to tell if it’s included. Soy milks, sausages, ice creams, cheeses, regularly include soy protein isolate.

            2. Hi Dr. Greger, there is some confusion over what constitutes three to five servings of tofu, using your citations. A bit more clarification would be very helpful. How many grams are you calling a half-cup of tofu? (Manufacturer labels don’t usually show this).

              It seems that food manufacturers use different readings:

              Wildwood tofu Super Firm lists a serving as 3 oz (85 grams, 130 calories, 14grams protein).
              Tofurky sausages indicate a serving as 3.5 ounces (100 grams, 380 calories, 30 grams protein).
              Westsoy Soy Milk indicates a serving as 1 cup (8 fluid ounces, 100 calories, 9 grams protein).

              If you consider a half-cup of tofu to be about two ounces (which is what USDA uses for “a serving”), then one could consume approximately one and a half to three Tofurky sausages, representing about 55 to 100 grams of protein a day. Does that sound consistent with your comments? Just trying to clarify for all of us.

              Thanks much.

            1. Hi. I have read the sources cited. The ONLY number that I was able to find was 11g/day of soy protein in the context that consuming more showed no improved protection against breast cancer. That seems rather low since 100g of tofu has more protein than this. I also looked at the chart that you posted above indicating the protein content in various soy products for 100g. Soy protein content varies greatly. I do not know how to interprete these values. I understand that you want us to search and think for ourselves, and I really have done my best to find the number. Can someone please help me and plainly answer the question: How many grams of soy protein a day should be consumed at most total (not per serving)?

          2. I agree. I’m trying to find out how many grams of soy protein per day is ideal. Maybe it’s somewhere in the articles that HemoDynamic posted but surely someone has read it and can post here so we don’t all have to read it.

            The most complete article I’ve seen on soy is: When I read it before I understood him to say not to go over 20 grams but I can’t find that now so maybe he’s changed it. Elsewhere it is recommended to have at least 25 grams of soy protein so I would stick to that amount just to be sure unless the info above supersedes it.

        2. I will be consuming roughly 18 oz of soy per day, mainly tofu. This still falls just short of the 5 servings per day in the healthy range (based on the 100 grams is 1 serving study). Just asking if I have interpreted this correctly before consuming this much soy


      1. Tamsel: It I my understanding that there are some studies on both sides of the argument, just like there re studies on both sides of the smoking argument. But it is also my understanding that the vast majority of studies, especially those done on humans, show that traditional soy products (like tofu, tempeh, soy milk, etc) are quite healthy. Here is a summary of the information found on NutritionFacts concerning soy and which have a lot of studies to back it up:
        You mention that you consume “quite a bit” of soy every day. I don’t know what that means. But I think you can use the information from the video on this page and compare to what you consume to decide if you eat a reasonable amount of soy or not.
        Hope that helps.

      2. Part of the problem is the source Newsmax. If you see anything from that source it can be expected to not only be inaccurate, but also propaganda or sensationalism.

    2. Hello Michael Greger, I have organic soya milk in my tea so I have about 160 mls to 200mls per day. Is that too much? BTW it’s made from Australian grown organic whole beans never soy isolate.

    3. None of the studies you cite support a correlation of soy intake with increased IGF-1. The “Dietary soy and fats in relation to serum insulin-like growth factor-1 and insulin-like growth factor-binding protein-3 levels in premenopausal Japanese women.” study showed “no significant correlation between soy product as well as soy isoflavone intake and serum IGF-1 or IGFBP-3 levels after controlling for age, total energy, percent body fat, and education level. ..”
      The “Relationship of dietary protein and soy isoflavones to serum IGF-1 and IGF binding proteins in the Prostate Cancer Lifestyle Trial” study stated “These results suggest that dietary protein and soy isoflavones, in the context of comprehensive lifestyle changes, may not significantly alter IGF-1.”
      The “Insulin-like growth factor-1 and binding protein-3 in a 2-year soya intervention among premenopausal women” study states “similar mean IGF-1 and IGFBP-3 levels by group”. They did find a correlation between urinary isoflavone excretion during the study period and IGF-1 but that seems weak support, especially since other research specifically states isoflavones don’t seem to make a difference.
      Also I happened upon this study “Insulin-like growth factor-I, soy protein intake, and breast cancer risk.” that showed soy intake associated with lower IGF-1 and with increased (protective) IGFBP-3 levels.
      Could you cast your discerning critical eye to the data implying soy could be dangerous because of an impact on IGF-1? If it does increase IGF-1, perhaps the risk is offset by the increase in protective IGFBP-3 levels?

      1. Thank you for your question. This video may help answer some of your question.
        At moderate intake – 3-5 portions of soy a day there does not appear to be an adverse effect on IGF1 levels and you are correct there is an increase in IGF binding protein levels. However, it is when you get over 7 portions a day (which i suspect is pretty difficult to do and much higher than the intake in most asian countries), you may lose some of the beneficial effects of soy. I think there is no doubt that the inclusion on soy, and other beans, is beneficial to health, including for cancer prevention

    4. Dr Mcdougall has referenced some studies showing that soy protein isolate raises IGF-1 levels even more than dairy protein.

      Have there been any more studies confirming this? Anybody know why this isn’t better known or discussed? Is it because so many expensive modern foods depend on soy protein isolate for their rich taste?

        1. Hi, thanks, this is definitely interesting!

          To me, this study confirms 100% McDougall’s recommendation to avoid soy isolate and eat traditional soyfoods as Asians do, not add a seaweed supplement to somewhat counteract the damage from soy isolate. Soy isolate shouldn’t really even be part of soy foods as a general category as if getting x grams of soy protein isolate is just like eating that much from tofu or soybeans. We don’t say that gluten is just part of ‘wheat foods’.

          Pretty disturbing how little the dangers of soy isolate, as shown by experiment, are known or discussed, and how prevalent they have become. People are all owed to assume that eating a sausage made of soy isolate is like eating tofu as healthy Asians do.

          Are there any studies that contradict Dr Mcdougall’s conclusions?


  2. Would quinoa fall into the same category as soy since it’s also a whole protein?  I’m sure most people don’t eat as much quinoa as soy, but it increasing in popularity.  There are lots of recipes that call for quinoa and tofu.

      1. I realize that it’s a seed, but it’s a complete protein just like soy and animal products. The point of the video is that since  soy is a complete  protein, like meat, out bodies make more IGF-1.  Since quinoa is a complete protein, like meat, will it also cause our bodies to produce more IGF-1.

        1. One of the best ways to consider “completeness” of a protein (in quotes, because as many wise commenters have pointed out, there are a variety of ways to assess this) is to look at the protein digestibility–corrected amino acid score (PDCAAS). While this method has limitations, it is the Food and Agriculture Organization/World Health Organization (FAO/WHO) preferred method for the determination of protein value in human nutrition. This takes into account not just the amino acids in a given food, but how the digestibility of that food affects the bioavailability of the protein in it. According to the PDCAAS, 1 is the “most complete” and 0 is the “least complete,” with milk, eggs, and soy ranking at 1. While quinoa is considered a “complete protein,” its PDCAAS is slightly less than 1, due to the presence of other nutrients and fiber, which may reduce digestibility.

          What does this mean? Probably, not much, as long as you are eating a varied plant-based diet that contains plenty of vegetables, fruit, nuts, and seeds. As with all things in nutrition, variety and moderation are probably the best way to “hedge your bets,” in terms of ensuring a healthy diet, without overdoing it on any one food. And according to Dr. Valter Longo, a researcher studying the effects of dietary protein on health, there is convincing evidence that a high-protein diet — particularly if the proteins are derived from animals — is nearly as bad as smoking for your health, BUT, the big caveat: These effects were either abolished or reduced in individuals eating a high-protein diet that was mainly plant based. This suggests that even “complete” plant-based proteins are an excellent choice for optimal health.

          Based on all of these factors, I believe that having quinoa in the diet is a net positive for health, so long as you’re not eating quinoa morning, noon, and night, every single day.

        2. “Complete protein” is completely different from “completely protien”. It simply means that it is approved of in the out-dated “combining proteins” models. If you get protein from any different sources that are not closely related (eg. rice and legumes) you should be fine. A bigger concern is, like salt, with getting too much protein, which will be the case if you swap out the Quinoa with Chicken breast and steak.

        3. I have a sneaking suspicion that the day of a really, really, hard and strenuous resistant exercises or extreme cardio, high quality protein and resultant IGF would be used accordingly and properly. Not insane amounts but yes, high quality protein and perhaps closer to 1.7 grams protein for each kg of lean body mass. For that day alone. Perhaps for just the next several hours after the workout and then go back to normally low protein. The next day just the normal and usual beans barley and whatever plant food and only .8 grams protein per kg of lean mass. I think that is sort of what Dr. Longo recommended. Michael Phelps allegedly eats 10000 calories each day with his workouts but if you or I tried to do that, you know what will happen. It’s ok for him but he’d get everything bad under the sun if he stopped swimming……… just like every one else.

      2. Quinoa is a seed, but nutritionally it is a grain, as peanuts are bean, but nutritionally a nut, as tomatoes are a fruit, but nutritionally a vegetable.

        1. Toxins, you are so amusing.

          I guess my point was more that the series was on soy not quinoa.

          Today’s video (0october 9th) will upset quite a few. I hope you are armed with the appropriate articles. Someone has to do it!

    1.  Liz: I don’t
      know if quinoa has been studied as extensively as soy or not.  So, how would we know?

      But I did want to point out that the concept of “complete” protein
      doesn’t make sense.   All proteins are complete proteins.  The
      difference is that some proteins have closer chemical make-ups to human flesh
      compared to other proteins.

      I have also heard about quinoa being a “complete” protein.  Even
      though this description is irrelevant, I would guess that people use it to mean
      that quinoa has a closer profile to mammal proteins, just like soy.  So, I
      think it is possible that your idea could be correct.  But I think it
      would depend on the answer to the question: just how close is the quinoa
      protein to animal protein?  Is the difference significant enough to make
      quinoa behave more like other plant proteins or more like soy?


      I don’t think we know the answer to this question.  However, I have an idea for you.  if you are interested, you can go to
      the following site and get protein profiles (amount of each type of amino acid)
      in various foods.  You could use this
      site to compare percentages and see how say soy and quinoa differ in amino acid
      percentages from say chicken and beef. 
       It would be interesting even if
      not conclusive to anything.
      To get to the protein profiles: (1) Type a food at top and press search.  (2) click into the food that you are
      interested in.  (3) scroll to the part
      that mentions the protein and click the little down arrow/tab.  When you do that, you will see a list of the
      amino acids and the amounts of each one. 
      (4) copy that data into a spreadsheet to calculate percentages if you want.

        1.  Wow.  That’s like the best compliment ever. You have made my day!

          And may I also say that I enjoy reading your posts as well.  I think that the comments under the videos are an important part of this site.  Your good quality comments add to the whole.

          1. I might be missing something, but i think the “completeness” some people refer to is the fact that soy, like animal proteins, contain the 9 essential amino acids that we cannot make ourselves by eating other stuff..

            I mean, we can construct the majority of proteins by eating carbs and fat, but not the 7 essential amino acids :D

            Soy has them! :P I dont eat alot of soy though.. If you combine lentils/beans with Rice or wheat protein, you will get all the essential AA*s :)

            1. HI Ali,

              All plant foods contain all the amino acids. When people refer to “completeness”, what they really mean is the ratio of amino acids. This also does not matter, as our body can draw from the circulating pool of amino acids over the course of the day. Thus, we do not need to try and eat “complete” within the same meal, or even the same day. Protein deficiency will never occur as long as one consumes enough calories of whole plant foods.

              1. I see what you’re saying, but iv’e always read that you had to complete the protein profile within same meals / days..
                Im not saying that you are wrong, but do you have anything to back it up? where did you get that info? :) I wanna read about it :P

                1. Hi Ali, You can go to the USDA food database and search any plant food. You will find that they all contain the essential amino acids. Regardless of what you have heard (I have heard the same), no plant food is missing any amino acid.

                  “Plant protein can meet protein requirements when a variety of plant foods is consumed and energy needs are met. Research indicates that an assortment of plant foods eaten over the course of a day can provide all essential amino acids and ensure adequate nitrogen retention and use in healthy adults; thus, complementary proteins do not need to be consumed at the same meal ”


                  Here is Jeff Novick, an excellent plant based dietician, expanding greatly on the topic


            2. Ali: Toxins gave a really great, concise response. If you want to learn more, here are my favorite resource for understanding human protein needs and what “completeness” means in terms of human health:

              To fill in yet some more details is Dr. McDougall article from December 2003.
              You might also check out the January 2004 newsletter article, Protein Overload.

    2. Liz, the concern is with getting too much of the protein, not just the “completeness” of it which only has to do with ratios. A cup of soybeans has 22 grams of protein while a cup of quinoa has only 8. If IGF-1 levels were an issue with quinoa, which i doubt, one would have to eat several cups worth to get to 1 serving of soy.

    3. Hi, Liz. The only study I have found on quinoa and IGF-1 was done on malnourished children. In the study, the children consumed 100g of a quinoa slurry twice daily. It did increase serum IGF-1 in those children, but that would most likely be beneficial for malnourished children, and may not be indicative of its effects in healthy adults. I suspect that a person would have to consume a lot of quinoa for that to become a problem. I hope that helps!

  3. I’m with the folks asking “what is a serving”? For me, a serving has been:

    8 ounces of edamame (in the pod0.
    7 ounces of tofu
    11 ounces (by weight) of plain unsweetened soy milk (about 1/3 of a quart container)

  4. Didn’t yesterday’s video say that IGF-1 binding increased along with  IGF-1 levels in those eating lots of soy which explained why east Asians who consume lots of soy do not get the cancers of those with high IGF-1 levels obtained from animal protein?

  5. Now we know how much soy is “safe” to eat to not raise IGF levels…but what about how much soy is safe to consume to not affect the thyroid and hormone balance due to the possible phytoestrogens and goitergens?

    And does the sprouted soy offer the same “protective benefits” as fermented soy?

        1. Yes it does, the study regarding the neutral benefits were specifically in regards to men. For women, the studies all show better health outcomes in terms of breast cancer prevention.

        2. There were some pretty conclusive studies that suggested tofu is bad for you coming out of Thailand. It turns out the problematic ingredient was formaldehyde. If you get tofu from Thailand it is probably good to verify that you get the non-formaldehyde version.

          The phytoestrogens were based on chemical similarity, but there are actually two relevant receptors – a down-regulator and an up-regulator. The harmful estrogens trigger the up-regulator, I believe, and soy triggers the down-regulator. That’s from memory so double check me.

  6. Hi Dr Mike,  I emailed you recently and you asked me to publish in the comments.  I cant find an exact topic that suits so Im asking here:

    1.  Can you explain the difference (in chemistry and the way our bodies utilise it) between “estrogen” from animals and “phytoestrogen” in plants which mimics estrogen in humans?

    2. Is there any evidence for the effects on vegan diets for Poly Cystic Ovarian Syndrome (PCOS) ?

    Thanks again and keep up the good work!


  7. I thoroughly enjoy your videos and am so excited to have found your website, Dr Greger. Thank you for providing this great resource!

    I am new to the principle of limiting animal protein intake to prevent cancer. After reading the ‘China Study’ two years ago, I changed my family’s diet. This was the information that I had been searching for, as my oldest son had been subjected to a lot of x-rays when he was a toddler. The realisation that all this radiation could result in problems later in life, made me hunt for a way of reducing any risks to his health. Since then I have also discovered un-denatured whey protein. The clinical studies certainly indicate that whey is useful for preventing and treating cancer. I immediaitely put my family onto whey protein and find that it certainly boosts the immune system as we all have far fewer colds despite having young children who bring home anything that is going around at school.

    I know that this is off the topic, but after watching all these videos reinforcing the role of animal protein in the promotion of cancer, I cannot help but wonder if whey protein is as good as our experience demonstrates it to be. I wonder if anyone can clarify whether the benefits of un-denatured whey protein (increase in glutathione) outweigh the negatives of consuming animal protein.

    Also, any advice on what else to do to prevent the potential negative effects of the radiation would be appreciated. I am slowly ploughing through all the videos but I will be grateful for any shortcuts.

    Thank you!

  8. Has anyone else come across the suggestion (e.g. as from that it’s fermented soy which is best for us? That means tempeh, miso and tamari soy sauce – the last two high in sodium!! Does the fermentation process alter the sodium for the better??

    1. noelene: I have heard several people report that fermented soy is best. However, I have also read (now I can’t remember where) that that is a myth. And Dr. Greger’s videos along with other sources seem to indicate that soy does not have to be fermented to be beneficial. Hope that helps.

    2. Naturopath physician, Joseph Mercola, NMD, who is not a vegetarian or vegan, has indicated that the only soy one should eat, assuming it is certified organic, is fermented soy because he says fermented soy has vitamin K2, a little known vitamin which is amongst other data, is beneficial in keeping calcium in the bone and not leaching out into the blood stream. He cites fellow naturopath, (and grass fed meat eater) Kate Rheaume-Bleue, a graduate from Toronto’s Canadian College of Naturopathic Medicine in 2002. More about Dr. Kate at

      She authored the book: “Vitamin K2 and the Calcium Paradox: How a Little-Known Vitamin Could Save Your Life,” available at

      Dr. Andrew Weil, M.D. also recommends supplementing with vitamin K2 especially if one has been diagnosed with osteoporosis, which I have. But, I would rather get some vitamin k2 from food and flavor my dark leafy greens with Eden Organic Shiro Miso, which is lower in sodium content than most other misos. According to Eden Foods, the Shiro has 330 mg sodium per tablespoon. Additionally Eden (is certified) Organic and non-GMO Project verified. This is one of the few food company’s worthy of trust, in my opinion.

      I would still be interested in reading Dr. Greger’s input on this book as well as scientific studies.

    1. A study to determine normal values of serum IGF-1 in adults, ages 21-70 years old, found that there was no difference in the values observed between healthy men and women. However, a progressive reduction in IGF-1 levels was seen in advancing age. Below is what the study found (1).

      Reference values (mean ± 2 SD) Age IGF-1

      21-25 years 115-345 μg/L

      26-30 years 116-324 μg/L

      31-35 years 112-300 μg/L

      36-40 years 105-280 μg/L

      41-45 years 97-263 μg/L

      46-50 years 90-249 μg/L

      51-55 years 84-236 μg/L

      56-60 years 78-222 μg/L

      61-65 years 72-210 μg/L

      66-70 years 66-198 μg/L

      71-75 years 61-186 μg/L

      76-80 years 57-174 μg/L

      81-85 years 52-164 μg/L

      1. Rosaria P W., Normal values of serum IGF-1 in adults: results from a Brazilian Population. Arq Bras Endocrinol Metab 2010;54/6.

  9. Hi, I recently read an article suggesting people should avoid foods such as tofu, soymilk and tofurky because they contain soy protein isolate. The article was concerned with the fact that SPI is highly processed. Granted whole foods are better for me, but as a vegan, I eat a lot of tofu. It’s convenient and tasty. Is SPI really something I should avoid?

    1. Patricia: I’m not an expert, so I can’t comment authoritatively. However, it is my understanding that normal traditional soy foods like tofu, soymilk, and tempeh contain NO soy protein isolate. Yes, they contain soy protein, which as far as we know is very good for you as part of a traditional soy food. However soy protein and soy protein isolate are two different animals. It’s like talking about beets and beet sugar. One is good for you. The other? No so much.

      Now, “processed” foods (non-traditional foods sold in packages like tofurky and snack bars) on the other hand, often DO have soy protein isolate added. THOSE foods are probably not so good for you in large amounts anyway. At least I have read that soy protein isolates can increase ifg-1 levels as much or more than dairy. I don’t know if that is true or not, just repeating what I have heard.

      I have read several essays and chapters on soy and gone to lectures from experts and watched Dr. Greger’s videos. The bottom line is: the science currently tells us that traditional soy products (including tofu) are not only NOT bad for you, but likely have a protective/healthful effect.

      Hope that helps and best of luck.

  10. Were the participants involved in this study fed organic soy or GMO soy? Also known as Roundup ready soy crops. That bit of information would be helpful in determining how effective this study was.

  11. Tofu, soymilk, soy yogurt are an extract from soy beans, with okara being the remaining pulp. Would eating okara with tofu etc have an effect? Thanks

  12. Soy is a legume native to East Asia, widely grown for its edible bean. Quinoa is a grain-like crop grown primarily for its edible seeds. Quinoa is closely related to species such as beets or spinach, according to Wikipedia. Quinoa can be substituted for rice and eaten with soy or other beans and lentils..

  13. I have just read here that ‘Besides the fact that nearly all non-organic soy ingredients are of GM origin, most soy additives are processed using a toxic chemical known as hexane, which is linked to causing birth defects, reproductive problems, and cancer. Soy that has not been fermented is also highly estrogenic, which can throw your natural hormone balance out of whack. ‘ What do you think of it? If it is true, how can I find THE SOYA?

  14. Have you come across any studies that link soy consumption to functional ovarian cysts? Some sources suggest eliminating soy products from one’s diet if she wants to prevent/treat follicular ovarian cysts (since hormonal imbalances or excess estrogen seem to cause them). I consume soy daily and periodically develop functional cysts, so I’d love to know if there is any scientific merit to these suggestions.

  15. I know a child who is nine months old that had a number of problems with cow’s milk formula. So I have recommended that the child use soy formula. The mom says the child vomited the soy formula but does well with the regular soy milk. The problems resolved but the child has not gained weight over the last 3 weeks. The child’s pediatrician says to go back to cow’s milk because of the estrogen effects of soy. We know cow’s milk is not a healthy option, but I can find no studies that provide a good evidence base for using soy milk (not formula) in a child under one year of age. Any thoughts? Also, does not cow’s milk formula contain IGF1 or is the IGF1 processed out of infant milk formulas?

    1. Charlie: I don’t have a full answer for you, but I wanted to share a couple of points.

      re: “The child’s pediatrician says to go back to cow’s milk because of the estrogen effects of soy.”
      Soy has plant estrogen, but cow’s milk has estrogen-estrogen. If estrogen is really a concern for this doctor, the last thing he/she should be doing is recommending cow’s milk. Some of these videos may prove helpful:

      These videos show other problems with babies and dairy milk:

      Plus, I want to mention that Dr. McDougall believes that there is a connection between dairy milk and type 1 diabetes. I don’t personally have that research, but my experience is that Dr. McDougall doesn’t make claims without data to back it up.

      I like the following quote from the following NutritionFacts article because it quotes Dr. Spock. (There is a video which covers this in a smidge more detail somewhere.):

      “Breast is always best, but the breast milk of women eating plant-based diets may be better still since they not only reduce or eliminate exposure to bovine casomorphins, but also contain lower levels of industrial pollutants like dioxins. See, for example, my 4-min. video Flame Retardant Chemical Contamination. For other effects animal products may have on healthy development see Dairy & Sexual Precocity and Protein and Puberty. No wonder Dr. Spock—the most esteemed pediatrician of all time—ended up recommending children be raised without exposure to meat and dairy.”

      On the other side, while I don’t know about any specific research on soy and babies, we do know that soy is generally protective/very healthy for older humans. There are plenty of videos on this site to that effect.


      Concerning: “Also, does not cow’s milk formula contain IGF1 or is the IGF1 processed out of infant milk formulas?”

      The issue with diary is that it contains animal protein. And animal protein convinced the body to create more IGF1 than might be healthy. Cancer loves extra IGF1. So, the issue is *not* that dairy contains IGF1 so much as that it triggers the human body to create excess IGF1. This site has a wonderful series on this topic. Check out these titles:

      • IGF-1 as One-Stop Cancer Shop
      • Cancer-Proofing Mutation
      • The Answer to the Pritikin Puzzle
      • Protein Intake & IGF-1 Production
      • Higher Quality May Mean Higher Risk
      • Animalistic Plant Proteins
      • Too Much Soy May Neutralize Benefits
      • How Much Soy Is Too Much?
      • Plant-Based Bodybuilding

      Hope that helps!

  16. Hello, I would like to know what the doctor recommends for people with low thyroid function. I would also like to know more about thyroid fiction and how diet effects it in general.

  17. Should I be worried about getting too much protein from other plant foods? Like should I watch my bean & lentil intake to make sure I’m not getting too much protein?

  18. So what is the conclusion regarding the 3-5 servings per day?

    It is a little frustrating to now know a number (like 3-5 servings) but still to be totally clueless regarding the daily intake in the form of soybeans, soymilk and tofu.

    Referring to the studies doesn’t help much, because the majority is only available through sites where you have to either pay for the full text or be a member of a scientific research program to get access.

    So what’s the latest consensus regarding soy beans or soy protein? If possible in grams per day please.

  19. I have a few questions regarding the safe intake levels of soy: Do the current “safe” limits (3-5 servings) for soy products extend to women with endometriosis? And is IGF-1 a different component than estrogen? How about the levels in infant formula, do they exceed the 3-5? Also, how much is a serving in respect to the variety of soy products out there and their concentrations, or what would be a serving of isolated soy as an ingredient versus a serving from a whole soy product such as edamame?? THANK YOU.

  20. Thanks! What do you think about Medifast? That has a lot of soy protein isolate, and you get about 50 g of soy protein a day while losing 10 lbs a month…I figure it’s more life saving to lose the weight than life damaging to consume the protein…what do you think?

  21. While this video covers soy recommendations in regards to IGF levels, it does not consider the other detrimental health effects of eating soy products. A health website recently reported that:

    The majority of soybeans (over 80%) are genetically modified, and they contain one of the highest levels of pesticide contamination of all foods.

    – Soybeans also contain hemaglutinins, which cause red blood cells to clump together. Soybeans also have growth-depressant substances, which are not fully eliminated by processing.

    – Soybeans are a source of natural toxins, also known as antinutrients, which means that they also contain a large quantity of inhibitors that deter the enzymes needed for protein digestion. In addition, these enzyme inhibitors are not completely disabled during ordinary cooking, so they often cause extensive gastric distress and chronic deficiencies in amino acid uptake, which can afterwards cause dangerous pancreatic impairments and cancer.

    – Soybeans are also very high in phytates, which prevent the absorption of minerals which are co-factors for optimal biochemistry in the body. These include calcium, magnesium, iron and zinc.

    – Soy contains goitrogens, which are often linked to depressed thyroid function.

    All claims are hyperlinked to online empirical studies, which has me worried about the amount of soy I’ve been eating since going plant-based (roughly 1-2 servings a day)

    Any closure on this would be really helpful!

    1. Nate: Those bullet points are concerns raised by the paleo crowd and are easily countered.

      The devil is in the details. Take for example the concern that over 80% of soybeans are genetically modified. Let’s assume for the moment that number is true. What is also true is that the vast majority of those GMO beans are fed to animals. Just try to find say tofu that is GMO. It is really hard where I live. Every box I have seen either says “organic” (which means GMO-free) or specifically says, GMO-free. GMO soybeans in human food is likely to be in highly processed foods (maybe a fake meat), something you would want to avoid anyway. Stay away from animal and processed foods and your soy should be fine.

      Another example we can easily debunk is the concern over “phytates” (which is usually the same substance listed as the big “anti-nutrient”). Dr. Greger has some great videos covering the health *benefits* of phytates

      Rather than address each bullet point: When I see lists like this, I find it helpful to step back and take a look at the big picture. The bottom line is that some cultures of very, very healthy people eat plenty of soy every day and do very well. Your 1-2 servings (assuming we are talking about traditional soy products like tofu, tempeh, soy milk, miso, etc) is very conservative. If this is the only NutritionFacts video on soy that you have seen, I recommend taking a peak at some more. I think it will help you with your concerns. The following overview page was updated just last week!

      My take-away is: You may want to re-think visiting that “health website”. And good for you for eating 1-2 servings of soy a day. The best science we have says that you are doing your body good.

      Hope that helps.

  22. Dr. Greger, WHO just updated their cancer warnings to include processed meat and red meat. It seems like a lot of the worry has to do with cooking animal protein at high temperatures. What about vegan mock meat that is made with large concentrated amounts of pea protein or soy protein or wheat protein?

  23. I am having 100grams boiled soybeans everyday to complete my protein need for muscel building. I keep dry beans for soaking and then boil. Am I doing right?

  24. trying to form a unbiased opinion about Soylent (the “superfood”?/all in one nutrition pack).

    My current thoughts, before I’ve done much research is that I’m sceptical. My reasons for being so is based on a few things, but I dont know if they’re really something to worrie about.

    so, Soylent is vegan (good, you won’t find any Cholesterol here! or animal suffering). However, it’s not GMO-free, though this is not necessarily something to worry about, as I think GMO’s can be safe (give me warning if there something you what to highlight about GMO’s. I’m under the impression that it’s not always bad, nor always good, and can be used with care).

    It contains large amount of Algal Oil (of which I have no clue about).

    one serving is 400 calories by (414 ml liquid), gets a wopping 190 of those from fat (!) ?? (explain this to me), although only 2 grams of saturated fat, and no transfat or cholesterol. 20 grams of protein from (soy protein isolate, please tell me how many servings of soy protein isolate that is with regards to IGF-1 risk factors), only 3g of dietary fiber, 9 grams of sugar and a total for 37 grams total carbs. Furthermore it contains 300mg of sodium and 700 mg of potassium and about 20% of daily recommended values of all vitamins and minerals. Marketed as “a complete meal” and that you could live of it.

    I’m not interested in Soylent for my own consumption, but a friend of mine is convinced that it’s very good, and was sceptical towards my sceptisim as he himself have done a lot of research on it already, coming with good logical arguments and anecdotal evidence that people who have been eating it for a while don’t have any deficiencies and therefore it’s good for you.

    Could Dr. Greger make a video about Soylent? or alteast anyone give me something about Soylent or the possitive or negative effects of the ingredients? Soy protein isolate seems to be a good source of Arginine for example.

  25. Hello doctor!!
    I would like to know if a cup of soy beans per day is harmful???
    After boiling them…it turns out to be atleast 2 cup of soy beans…so is its consumption each day harmful???if yes…how much soy bean should i have per day???

    1. At the end of the video, Dr. Greger says that 3-5 servings/day of legumes is ideal. One serving is 1/2 cup, so your 2 cups of soy beans should be fine. That said, “variety is the spice of life” and also of good health. Why not mix it up and have some other beans and plant-based protein sources some days? The more variety you get, the more likely you are to get all the wonderful health benefits a WFPB diet can offer.

    1. Great timing on your question, Craig. Check out today’s video on protein: Protein video

      As the video explains, protein deficiency is unlikely for anyone eating a WFPB diet, but there is a common myth out in the world that humans need meat for health.

  26. Regarding soy. In Mexico (where we reside part time) they have a soy product that is commonly used by Mexicans. It is de-defatted by removing The Oil is removed from the soy with Hexane an oil product. The end product is a TVP (textured vegetable protein). Are their any studies on this product. Also to be considered is that the soy may be a GMO. The second process by which oil is extracted is by using a squeeze process for extraction of oil that results in a similar dry soy product that may be activated by adding water. It is this product that is used in making soy meat prducts as a substitute for animal meat products. We have a recipe for making veggie burgers that we make on a regular basis. We maintain the three to five servings per day consumption limitations in our failing eating schedule. The laboratory studies regarding the use of Hexane on laboratory rats reveal there are dangers in consuming Hexane. The massive quantities of this on rats in studies does not nearly equal the residue left in de-fatted soy. Yes there is risk on use of oil products in oil extraction of soy. My concern is it a product that should be avoided. Your comments will be appreciated.

    1. jpmex1946: I am familiar with TVP as it is readily available in the US as well. I am also familiar with the hexane concern. I have read that the amount of hexane left in the TVP varies quite a bit depending on the manufacturer and also that the levels in TVP are small enough not to worry. But like you, I’m not so comfortable with it.
      I don’t know if you can get it in Mexico or not, but there is a product in the US called Soy Curls, which has a texture and cooking preparation similar to TVP, but Soy Curls are just the whole soy bean. I do not believe that they use Soy Curls in the processing. There is a dehydration process, but they don’t remove the fat I don’t think. If you could get this product shipped to Mexico, I’m thinking it might be the best of both worlds – ie, being able to use your TVP recipes without having the health concerns. It’s just an idea. If you want to learn more, you can do a web search for “Soy Curls vs TVP” and come up with some interesting articles. And also here is the website for the company:
      I hope others will jump in with their opinion of TVP as I am also interested.

  27. I keep coming across that soy can suppress thyroid function. Is this true? I take bio identical thyroid and would like to know if soy is ok for me?

  28. So how many Smart Dogs (soy protein isolate dogs) can I have per day, if no other soy? I can’t make head or tail or the serving size/grams/ounces discussion. Please, I just want to know if I’ve been overdoing my Smart Dogs when I eat three of them. Does anyone have this answer? I would surely appreciate help with this. Thanks.

    1. ArtichokeAddict: I would say that Smart Dogs are not so smart, because they include soy protein isolates. If it is not clear in this particular video, when Dr. Greger talks about the health advantages of soy foods, he has made clear in other videos that he is talking about traditional soy foods: tofu, tempeh, edamame, soy milk, etc. Isolated soy protein is not a whole food (it’s like making table sugar out of beets). I don’t have a reference, but people have reported that there are studies showing that soy protein isolate may raise IGF-1 levels as much as meat dairy and egg white.
      So, while Smart Dogs will avoid some health risks over animal-based “dogs”, they are not such a healthy food. I’m not an expert, but I would recommend eating Smart Dogs once a month or less as a special treat rather than daily. But having said that, if you are in transition from a SAD diet to a plant food diet, you may want to keep eating your Smart Dogs for a while as a stepping stone to transition you to the next step in healthier eating. For example, at some point, you might look into healthier alternatives, perhaps tofu that has been seasoned to taste like a hot dog and cooked so that it has a firm texture. (Just an idea.)
      FYI: In Dr. Greger’s new book, How Not To Die, he defines a serving of tofu or tempeh as 1/2 cup.

      I know it is not the news you were looking for, but I hope it helps.

      1. Thea: it certainly does help. I don’t have to worry about servings now. I’ll cut them out completely. I have cooked with tofu. It’s just that it takes so long and I really liked the speed factor of the fake dogs. And they were a vehicle for my homemade ketchup and curry. Now I’ll have to find something else to put ketchup on. But I very much appreciate the response! Thanks.

        1. ArtichokeAddict: re: convenience factor. I so get that! Your homemade ketchup and curry sounds awesome. I hope you are able to find a good and fast replacement.
          In case you are interested in some ideas (not as convenient as store bought fake meat, but maybe close):
          >> I can bake most sweet potatoes in my microwave in less than 10 minutes, and I think spuds would be a good vehicle for your gourmet condiments.
          >> Jeff Novick has a “Fast Food” DVD series. The second video is on making your own burgers and “fries”. But these burgers are truly healthy and are pretty fast/easy to make. And they would make an excellent repository for the ketchup and curry. Here’s how it gets better/faster: If you make a bunch of burgers and freeze them, the burgers are literally ready to go in 1 minute in the microwave whenever you want. And they seem to last a long time in the freezer. I try to always have some home-made burgers in the freezer ready for whenever I need a fast meal and don’t want to cook.
          >> Can of beans. Even just a can of beans might work for you, especially for the curry.
          re: “artichoke addict” I may not be an addict, but I too love artichokes. Just in case you happen to have a Trader Joes near you and were not aware: Trader Joes sells pre-cooked, quartered, frozen artichoke hearts. I just thaw and put in various dishes. So yummy and so easy.
          Good luck to you.

  29. Hello Dr. Greger, I have a question for you.
    According to Dr. John McDougall, fake meats and soy supplements (that are higly processed foods that contains high concentrates of protein soy) must be avoided because are cancirogens as makes increase production of IGF-1. Could you please make a new video telling if you agree with this posture or not? May be instead of just saying like in this video how many servings a day, you could speak about fake meats and soy supplements for bodybuilders? Or how much soy protein is too much may be?

  30. I’m interested in making my own soy milk, but dislike the strong “beany” taste that I get when I do. Miyoko Schinner’s book recommends not soaking the beans in advance (to avoid this beany taste), but I am wondering if NOT soaking them fails to eliminate some problem I’ve heard about regarding soy and thyroid function? So the question is, is the “soy is safe” message still true if the beans are not soaked before being made into soymilk or tofu?

  31. Silken tofu has soy protein isolate (for non-gmo) and soy protein (for organic) listed as the second ingredient behind whole soybeans. Would you, or others on this site recommend against it? Dr. Mcdougall is vehemently against soy protein isolate, but I am having a hard time finding the literature to support such an overwhelming apprehension towards it. Any information or citation would be greatly appreciated. Thanks to anyone who provides some insight!

  32. Soy is bad. Nasty stuff. I don’t care how much lower Japan’s breast cancer rate is than ours—-phytoestrogens can cause estrogen driven cancer. Plus I know how soybeans are raised. The herbicides and pesticides alone are enough to cause problems not to mention most of them are gmo’s.l

    1. Erin: Do you have any evidence to back up the following claim? “phytoestrogens can cause estrogen driven cancer.” The evidence I have seen shows the opposite. For example: Soy & Breast Cancer
      Also, it is easy enough to get organic soy, which means non-GMO. Most soy used in traditional soy products fed to humans (tofu, tempeh, edamame, etc) is non-GMO. Your claims about soy being bad do not seem to match the evidence.

      1. I apologize for my sweeping comment against soy. I was blaming soy for my estrogen driven cancer when it most likely was a combination of a dozen different factors. My doctor has told me to avoid all soy products, and I think many patients get this advice once they are diagnosed with that kind of cancer. Since I posted the angry comment about soy , I have learned that the sources of estrogen are everywhere. But I do think organic is safer than regular soybeans. Thank you for the video suggestions, Joan.

    2. Erin, Fortunately you can eat a whole food plant-based diet without relying on soy. However, before you completely eliminate soy from your diet you may want to check this video out which poinst out: Soy, like all beans is heart healthy.
      Soy Worth a Hill of Beans? |
      Studies are ongoing about GMO and pesticides and you may want to check this video out:

  33. I’m eating my daily dozen religiously but feel like it’s a lot of beans and my stomach is swollen and bloated. I imagine this is a transitional phase whilst my body adjusts. I was wondering though, I use soy milk in my oats and would like to know whether soy milk actually counts towards your daily serving of beans the way tofu does?

    1. Thanks for your comment,

      Whey protein intake leads to higher IGF-1 levels and increased TMAO activity, this could negatively affect our health in many different ways (1). Plus, whey protein has been found to be contaminated with various dangerous compounds (2, 3).

      I should not that soy protein would also lead to high IGF-1 levels, but a recent review suggests (4):

      “the evidence that large amounts (40 g/ day) of soy protein increase unbound IGF-1 in com- parison with dairy protein is unimpressive. However, it is possible that as a high-quality protein, soy protein may increase IGF-1 levels among those who do not con- sume animal protein, but the evidence in support of this speculation is extremely limited. Furthermore, all of the starting and ending IGF-1 values for both the control and soy protein groups fell within the normal reference range [83]. Given all of the evidence, a reasonable con- clusion is that a decision to incorporate soyfoods into the diet should not be based on the possible effects on IGF-1 system.”

      Nevertheless, Dr McDougall has an opposing view to the quote above mentioned about soy protein (5)

      When it comes to the environment, it is well established that the consumption of animal based foods (including whey protein) is the leading cause of the destruction of our planet and therefore such recommendations could worsen the current environmental state of the planet.

      Hope this answer helps.

    1. Dear spring03, good morning !

      Thank you for your reply.

      However, my question was how many grams are each serving of soy, for example each serving of soy equals to 120 grams of soy ? equals to 240 grams of soy ? something else ?

      Thank you again for your time

    1. Thanks a lot Christine! You brought more light(and exact number) into this :) Also regaring soy milk I found an interview with Dr. Greger where he calculates 1 serving of soy milk as 250ml = 1 cup(calculated from his statement that: “20 servings of soy = 5 litres of soymilk).

      Video source: (time 9:32).

      So if I got it right the bottom line is following:

      1 serving of cooked tofu or tempeh = 130g
      1 serving of soymilk a day = 250ml / 1 cup

      Therefore if 5 servings of soy a day is a high end it means that a smart move would be not to consume more than 650g of tofu/tepmeh a day or drink 5 cups/1250ml of soymilk a day.

      Also important to watch out for combinations e.g. 2 cups of soymilk in the morning in your smoothie + 195g of tofu for lunch and 195g of tempeh for dinner brings you also to the high end. It is not hard at all to consume this amount of soy products on a vegan diet.

      Take care everyone :)

  34. Two questions:

    1) How big is a serving in these studies?
    2) Is Dr. Greger saying that we should limit soy consumption to 3-5 servings a day, or all legume consumption to 3-5 servings a day?

  35. You asked if that 3-5 servings/day limit applied to all legumes or just soy. Just soy, since that is the food that has shown potential for increased IGF-1. You also asked how big a serving is in the studies cited. I reviewed the sources and sometimes there was no clarification of exact amount, just an indication that the subjects were consuming a soy food. In two of the studies serving size was more defined as “two daily servings of soya foods including tofu, soya milk, soya nuts and soya protein powder (equivalent to 50 mg isoflavones and 5-22 g soya protein per serving)” or “58 grams/day.” I think it might be more helpful to focus on what Dr. Greger and others have defined as a serving. I think some of the earlier comments spell that out-130 grams of tofu or tempeh, 1 cup soy milk.
    Hope that helps.

  36. I’m so sorry I’m still confused what specifically is meant by serving.
    In daily dozen Dr. Greger defines a serving of legumes as: : “A serving is defined as a quarter-cup of hummus or bean dip; a half-cup of cooked beans, split peas, lentils, tofu, or tempeh; or a full cup of fresh peas or sprouted lentils.”
    I have been buying dried soy beans (not green outer layer, just the dried beans) and cooking them with onions and tomatoe sauce just like one would cook any other dried bean— like how one would make chili.
    So when limiting the soy I eat to “2-3 servings a day” in order not to risk increasing IGF-1 should I treat it like any other dried legume. In other words if I limit the soy I eat to 2-3 half cups of cooked soy beans (without the green outer layer just the dried soy bean) is that right?
    My second question pertains to whether soy is good for leucine reduction.
    With deepest respect

    1. In other words I am asking if when Dr Greger suggests that in order to be safe we limit our soy consumption to 2-3 servings a day, if he means his own definition of a serving that I quoted above—- or if “serving” is defined differently in the people who have done research on too much soy consumption

    2. You’ve got it! About 1.5 cups a day of cooked beans will get the health benefits associated with them. A plant based diet has more than enough leucine for its health benefits without having so much that it can become pro-inflammatory. Whole soy beans, tempeh, and tofu are found to have health benefits.

      1. Thank you so much Mr. Manderson —so when the researchers say we need to limit soy to 2-3 servings a day in order for it not to be harmful they are using the same definition of serving as Dr. Greger?

  37. Hello, Dr. Greger !

    Thank you for the excellent video !

    I would like to ask how many grammars is one serving of soy, so as to calculate the recommended amount of 3 to 5 servings a day.

    Thanks in advance for your time

    Best Regards

  38. May you fix this reference, the link doesn’t work: Arjmandi BH, Khalil DA, Smith BJ, Lucas EA, Juma S, Payton ME, Wild RA. 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.

  39. I’ve only skim read this series of articles on soy but one thing strikes me…. I wonder whether it is the amount of soy that’s the problem, or the amount of protein? Yes soy is a complete protein but you get the complete amino acid profile by eating a variety of plant foods. So masses of beans and rice would give you masses of complete protein (albeit with more fibre and carbs I’d imagine). Soy products are just very easy to consume in larger amounts. I wonder if 7+ portions of chickpeas would have the same effect as 7+ portions of soy on IGF1? The varied vegans from the article on neutralising benefits probably weren’t consuming nearly as much protein as the soy heavy group. Plus the soy heavy group would presumable have been eating other sources of protein (grains…etc) on top of their soya. Does anyone know whether the studies controlled for protein intake? Sorry I haven’t got time to trawl the references!

    Also “3-5 servings is OK” really means “3 servings is OK”. Five servings was bad and we don’t know about 4. Also the amount that is OK for an individual will depend on protein requirements, surely? A 6’5” athlete will need more protein (and so may tolerate more soy) than a slender 5 foot women. So portion size will depend on the individual.

    For me the take home message here is to eat 3ish portions of legumes and make sure they’re not all soya. That way you can’t go wrong!

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